Merge branch 'master' of https://github.com/Z3Prover/Z3

CMakeLists.txt

@@ -187,6 +187,7 @@ endif()
 # Note for some reason we have to leave off ``-D`` here otherwise
 # we get ``-D-DZ3DEBUG`` passed to the compiler
 list(APPEND Z3_COMPONENT_CXX_DEFINES $<$<CONFIG:Debug>:Z3DEBUG>)
+list(APPEND Z3_COMPONENT_CXX_DEFINES $<$<CONFIG:Debug>:LEAN_DEBUG>)
 list(APPEND Z3_COMPONENT_CXX_DEFINES $<$<CONFIG:Release>:_EXTERNAL_RELEASE>)
 list(APPEND Z3_COMPONENT_CXX_DEFINES $<$<CONFIG:RelWithDebInfo>:_EXTERNAL_RELEASE>)
 
@@ -212,6 +213,16 @@ endif()
 ################################################################################
 include(${CMAKE_SOURCE_DIR}/cmake/z3_add_cxx_flag.cmake)
 
+################################################################################
+# C++ language version
+################################################################################
+# FIXME: Use CMake's own mechanism for selecting language version
+if (("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU") OR ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang"))
+  z3_add_cxx_flag("-std=c++11" REQUIRED)
+else()
+  message(AUTHOR_WARNING "Not setting C++ language version for compiler")
+endif()
+
 ################################################################################
 # Platform detection
 ################################################################################
@@ -244,6 +255,7 @@ else()
   message(FATAL_ERROR "Platform \"${CMAKE_SYSTEM_NAME}\" not recognised")
 endif()
 
+list(APPEND Z3_COMPONENT_EXTRA_INCLUDE_DIRS "${CMAKE_SOURCE_DIR}/src")
 
 ################################################################################
 # GNU multiple precision library support
@@ -287,6 +299,7 @@ if (USE_OPENMP)
     message(WARNING "OpenMP support was requested but your compiler doesn't support it")
   endif()
 endif()
+
 if (OPENMP_FOUND)
     list(APPEND Z3_COMPONENT_CXX_FLAGS ${OpenMP_CXX_FLAGS})
     # GCC and Clang need to have additional flags passed to the linker.
@@ -325,6 +338,8 @@ if (("${TARGET_ARCHITECTURE}" STREQUAL "x86_64") OR ("${TARGET_ARCHITECTURE}" ST
   unset(SSE_FLAGS)
 endif()
 
+
+
 # FIXME: Remove "x.." when CMP0054 is set to NEW
 if ("x${CMAKE_CXX_COMPILER_ID}" STREQUAL "xMSVC")
   # This is the default for MSVC already but to replicate the

contrib/cmake/src/CMakeLists.txt

@@ -35,6 +35,7 @@ endforeach()
 # raised if you try to declare a component is dependent on another component
 # that has not yet been declared.
 add_subdirectory(util)
+add_subdirectory(util/lp)
 add_subdirectory(math/polynomial)
 add_subdirectory(sat)
 add_subdirectory(nlsat)

contrib/cmake/src/shell/CMakeLists.txt

@@ -27,6 +27,7 @@ add_executable(shell
   opt_frontend.cpp
   smtlib_frontend.cpp
   z3_log_frontend.cpp
+  lp_frontend.cpp
 # FIXME: shell should really link against libz3 but it can't due to requiring
 # use of some hidden symbols. Also libz3 has the ``api_dll`` component which
 # we don't want (I think).

contrib/cmake/src/smt/CMakeLists.txt

@@ -55,9 +55,11 @@ z3_add_component(smt
     theory_dl.cpp
     theory_dummy.cpp
     theory_fpa.cpp
+    theory_lra.cpp
     theory_opt.cpp
     theory_pb.cpp
     theory_seq.cpp
+    theory_str.cpp
     theory_utvpi.cpp
     theory_wmaxsat.cpp
     uses_theory.cpp
@@ -68,6 +70,7 @@ z3_add_component(smt
     euclid
     fpa
     grobner
+    lp
     macros
     normal_forms
     parser_util

contrib/cmake/src/smt/params/CMakeLists.txt

@@ -8,6 +8,7 @@ z3_add_component(smt_params
     theory_array_params.cpp
     theory_bv_params.cpp
     theory_pb_params.cpp
+    theory_str_params.cpp
   COMPONENT_DEPENDENCIES
     ast
     bit_blaster

contrib/cmake/src/test/CMakeLists.txt

@@ -117,6 +117,7 @@ add_executable(test-z3
   upolynomial.cpp
   var_subst.cpp
   vector.cpp
+  lp.cpp
   ${z3_test_extra_object_files}
 )
 z3_add_install_tactic_rule(${z3_test_deps})
@@ -128,3 +129,14 @@ target_link_libraries(test-z3 PRIVATE ${Z3_DEPENDENT_LIBS})
 target_include_directories(test-z3 PRIVATE ${Z3_COMPONENT_EXTRA_INCLUDE_DIRS})
 z3_append_linker_flag_list_to_target(test-z3 ${Z3_DEPENDENT_EXTRA_CXX_LINK_FLAGS})
 z3_add_component_dependencies_to_target(test-z3 ${z3_test_expanded_deps})
+
+add_executable(lp_tst lp_main.cpp lp.cpp $<TARGET_OBJECTS:util>   $<TARGET_OBJECTS:lp>)
+target_compile_definitions(lp_tst PRIVATE ${Z3_COMPONENT_CXX_DEFINES})
+target_compile_options(lp_tst PRIVATE ${Z3_COMPONENT_CXX_FLAGS})
+target_include_directories(lp_tst PRIVATE ${Z3_COMPONENT_EXTRA_INCLUDE_DIRS})
+target_link_libraries(lp_tst PRIVATE ${Z3_DEPENDENT_LIBS})
+z3_append_linker_flag_list_to_target(lp_tst ${Z3_DEPENDENT_EXTRA_CXX_LINK_FLAGS})
+
+
+
+

contrib/cmake/src/util/lp/CMakeLists.txt

@@ -0,0 +1,35 @@
+z3_add_component(lp
+  SOURCES
+    lp_utils.cpp
+    binary_heap_priority_queue_instances.cpp
+    binary_heap_upair_queue_instances.cpp
+    bound_propagator.cpp
+    core_solver_pretty_printer_instances.cpp
+    dense_matrix_instances.cpp
+    eta_matrix_instances.cpp
+    indexed_vector_instances.cpp
+    lar_core_solver_instances.cpp
+    lp_core_solver_base_instances.cpp
+    lp_dual_core_solver_instances.cpp
+    lp_dual_simplex_instances.cpp
+    lp_primal_core_solver_instances.cpp
+    lp_primal_simplex_instances.cpp
+    lp_settings_instances.cpp
+    lp_solver_instances.cpp
+    lu_instances.cpp
+    matrix_instances.cpp
+    permutation_matrix_instances.cpp
+	quick_xplain.cpp
+    row_eta_matrix_instances.cpp
+    scaler_instances.cpp
+    sparse_matrix_instances.cpp
+    square_dense_submatrix_instances.cpp
+    static_matrix_instances.cpp
+    random_updater_instances.cpp      
+  COMPONENT_DEPENDENCIES
+    util
+  PYG_FILES
+    lp_params.pyg
+)
+
+include_directories(${src_SOURCE_DIR})

scripts/mk_project.py

@@ -11,6 +11,7 @@ from mk_util import *
 def init_project_def():
     set_version(4, 5, 1, 0)
     add_lib('util', [])
+    add_lib('lp', ['util'], 'util/lp')
     add_lib('polynomial', ['util'], 'math/polynomial')
     add_lib('sat', ['util'])
     add_lib('nlsat', ['polynomial', 'sat'])
@@ -52,7 +53,7 @@ def init_project_def():
     add_lib('smt_params', ['ast', 'simplifier', 'pattern', 'bit_blaster'], 'smt/params')
     add_lib('proto_model', ['model', 'simplifier', 'smt_params'], 'smt/proto_model')
     add_lib('smt', ['bit_blaster', 'macros', 'normal_forms', 'cmd_context', 'proto_model',
-                    'substitution', 'grobner', 'euclid', 'simplex', 'proof_checker', 'pattern', 'parser_util', 'fpa'])
+                    'substitution', 'grobner', 'euclid', 'simplex', 'proof_checker', 'pattern', 'parser_util', 'fpa', 'lp'])
     add_lib('bv_tactics', ['tactic', 'bit_blaster', 'core_tactics'], 'tactic/bv')
     add_lib('fuzzing', ['ast'], 'test/fuzzing')
     add_lib('smt_tactic', ['smt'], 'smt/tactic')

scripts/mk_util.py

@@ -774,8 +774,13 @@ def extract_c_includes(fname):
     linenum = 1
     for line in f:
         m1 = std_inc_pat.match(line)
-        if m1:
+        if m1: 
-            result.append(m1.group(1))
+            root_file_name = m1.group(1)
+            slash_pos =  root_file_name.rfind('/')
+            if slash_pos >= 0  and root_file_name.find("..") < 0 : #it is a hack for lp include files that behave as continued from "src"
+                print(root_file_name)
+                root_file_name = root_file_name[slash_pos+1:]
+            result.append(root_file_name)
         elif not system_inc_pat.match(line) and non_std_inc_pat.match(line):
             raise MKException("Invalid #include directive at '%s':%s" % (fname, line))
         linenum = linenum + 1
@@ -999,6 +1004,7 @@ class Component:
         out.write('%s =' % include_defs)
         for dep in self.deps:
             out.write(' -I%s' % get_component(dep).to_src_dir)
+        out.write(' -I%s' % os.path.join(REV_BUILD_DIR,"src"))
         out.write('\n')
         mk_dir(os.path.join(BUILD_DIR, self.build_dir))
         if VS_PAR and IS_WINDOWS:

src/ast/arith_decl_plugin.h

@@ -305,6 +305,7 @@ public:
     MATCH_UNARY(is_uminus);
     MATCH_UNARY(is_to_real);
     MATCH_UNARY(is_to_int);
+    MATCH_UNARY(is_is_int);
     MATCH_BINARY(is_sub);
     MATCH_BINARY(is_add);
     MATCH_BINARY(is_mul);
@@ -377,6 +378,9 @@ public:
     app * mk_real(int i) {
         return mk_numeral(rational(i), false);
     }
+    app * mk_real(rational const& r) {
+        return mk_numeral(r, false);
+    }
     app * mk_le(expr * arg1, expr * arg2) const { return m_manager.mk_app(m_afid, OP_LE, arg1, arg2); }
     app * mk_ge(expr * arg1, expr * arg2) const { return m_manager.mk_app(m_afid, OP_GE, arg1, arg2); }
     app * mk_lt(expr * arg1, expr * arg2) const { return m_manager.mk_app(m_afid, OP_LT, arg1, arg2); }

src/ast/rewriter/rewriter.txt

@@ -7,6 +7,7 @@ The following classes implement theory specific rewriting rules:
   - array_rewriter
   - datatype_rewriter
   - fpa_rewriter
+  - seq_rewriter
 
 Each of them provide the method
     br_status mk_app_core(func_decl * f, unsigned num_args, expr * const * args, expr_ref & result)

src/ast/rewriter/seq_rewriter.cpp

@@ -1434,6 +1434,7 @@ br_status seq_rewriter::mk_re_star(expr* a, expr_ref& result) {
  * (re.range c_1 c_n) = (re.union (str.to.re c1) (str.to.re c2) ... (str.to.re cn))
  */
 br_status seq_rewriter::mk_re_range(expr* lo, expr* hi, expr_ref& result) {
+    return BR_FAILED;
     TRACE("seq", tout << "rewrite re.range [" << mk_pp(lo, m()) << " " << mk_pp(hi, m()) << "]\n";);
     zstring str_lo, str_hi;
     if (m_util.str.is_string(lo, str_lo) && m_util.str.is_string(hi, str_hi)) {

src/opt/opt_solver.cpp

@@ -26,6 +26,7 @@ Notes:
 #include "theory_diff_logic.h"
 #include "theory_dense_diff_logic.h"
 #include "theory_pb.h"
+#include "theory_lra.h"
 #include "ast_pp.h"
 #include "ast_smt_pp.h"
 #include "pp_params.hpp"
@@ -143,6 +144,9 @@ namespace opt {
         else if (typeid(smt::theory_dense_si&) == typeid(*arith_theory)) {   
             return dynamic_cast<smt::theory_dense_si&>(*arith_theory); 
         }
+        else if (typeid(smt::theory_lra&) == typeid(*arith_theory)) {
+            return dynamic_cast<smt::theory_lra&>(*arith_theory); 
+        }
         else {
             UNREACHABLE();
             return dynamic_cast<smt::theory_mi_arith&>(*arith_theory); 
@@ -401,6 +405,14 @@ namespace opt {
             return th.mk_ge(m_fm, v, val);
         }
 
+
+        if (typeid(smt::theory_lra) == typeid(opt)) {
+            smt::theory_lra& th = dynamic_cast<smt::theory_lra&>(opt); 
+            SASSERT(val.is_finite());
+            return th.mk_ge(m_fm, v, val.get_numeral());            
+        }
+
+        // difference logic?
         if (typeid(smt::theory_dense_si) == typeid(opt) &&
             val.get_infinitesimal().is_zero()) {
             smt::theory_dense_si& th = dynamic_cast<smt::theory_dense_si&>(opt);

src/parsers/smt2/smt2parser.cpp

@@ -66,7 +66,7 @@ namespace smt2 {
 
         scoped_ptr<bv_util>               m_bv_util;
         scoped_ptr<arith_util>            m_arith_util;
-        scoped_ptr<seq_util>              m_seq_util;
+        scoped_ptr<seq_util>              m_seq_util;      
         scoped_ptr<pattern_validator>     m_pattern_validator;
         scoped_ptr<var_shifter>           m_var_shifter;
 

src/shell/lp_frontend.cpp

@@ -0,0 +1,111 @@
+/*++
+Copyright (c) 2016 Microsoft Corporation
+
+Author: 
+
+    Lev Nachmanson 2016-10-27
+
+--*/
+
+#include "lp_params.hpp"
+#include "util/lp/lp_settings.h"
+#include "util/lp/mps_reader.h"
+#include "timeout.h"
+#include "cancel_eh.h"
+#include "scoped_timer.h"
+#include "rlimit.h"
+#include "gparams.h"
+#include <signal.h>
+
+static lean::lp_solver<double, double>* g_solver = 0;
+
+static void display_statistics() {
+    if (g_solver && g_solver->settings().print_statistics) {
+        // TBD display relevant information about statistics
+    }
+}
+
+static void STD_CALL on_ctrl_c(int) {
+    signal (SIGINT, SIG_DFL);
+    #pragma omp critical (g_display_stats)
+    {
+        display_statistics();
+    }
+    raise(SIGINT);
+}
+
+static void on_timeout() {
+    #pragma omp critical (g_display_stats)
+    {
+        display_statistics();
+        exit(0);
+    }
+}
+
+struct front_end_resource_limit : public lean::lp_resource_limit {
+    reslimit& m_reslim;
+
+    front_end_resource_limit(reslimit& lim):
+        m_reslim(lim)
+    {}
+
+    virtual bool get_cancel_flag() { return !m_reslim.inc(); }
+};
+
+void run_solver(lp_params & params, char const * mps_file_name) {
+
+    reslimit rlim;    
+    unsigned timeout = gparams::get().get_uint("timeout", 0);
+    unsigned rlimit  = gparams::get().get_uint("rlimit", 0);
+    front_end_resource_limit lp_limit(rlim);
+
+    scoped_rlimit _rlimit(rlim, rlimit);
+    cancel_eh<reslimit> eh(rlim);
+    scoped_timer timer(timeout, &eh);
+
+    std::string fn(mps_file_name);
+    lean::mps_reader<double, double> reader(fn);
+    reader.set_message_stream(&std::cout); // can be redirected
+    reader.read();
+    if (!reader.is_ok()) {
+        std::cerr << "cannot process " << mps_file_name << std::endl;
+        return;
+    }
+    lean::lp_solver<double, double> * solver =  reader.create_solver(false);  // false - to create the primal solver
+    solver->settings().set_resource_limit(lp_limit);
+    g_solver = solver;
+    if (params.min()) {
+        solver->flip_costs();
+    }
+    solver->settings().set_message_ostream(&std::cout);
+    solver->settings().report_frequency = params.rep_freq();
+    solver->settings().print_statistics = params.print_stats();
+    solver->settings().presolve_with_double_solver_for_lar = params.presolve_with_dbl();
+    solver->find_maximal_solution();
+
+    *(solver->settings().get_message_ostream()) << "status is " << lp_status_to_string(solver->get_status()) << std::endl;
+    if (solver->get_status() == lean::OPTIMAL) {
+        if (params.min()) {
+            solver->flip_costs();
+        }
+        solver->print_model(std::cout);
+    }
+    
+//    #pragma omp critical (g_display_stats)
+    {    
+        display_statistics();
+        register_on_timeout_proc(0);
+        g_solver = 0;
+    }
+    delete solver;
+}
+
+unsigned read_mps_file(char const * mps_file_name) {
+    signal(SIGINT, on_ctrl_c);
+    register_on_timeout_proc(on_timeout);
+    lp_params p;
+    param_descrs r;
+    p.collect_param_descrs(r);
+    run_solver(p, mps_file_name);
+    return 0;
+}

src/shell/lp_frontend.h

@@ -0,0 +1,7 @@
+/*
+  Copyright (c) 2013 Microsoft Corporation. All rights reserved.
+
+  Author: Lev Nachmanson
+*/
+#pragma once
+unsigned read_mps_file(char const * mps_file_name);

src/shell/main.cpp

@@ -35,8 +35,9 @@ Revision History:
 #include"error_codes.h"
 #include"gparams.h"
 #include"env_params.h"
+#include "lp_frontend.h"
 
-typedef enum { IN_UNSPECIFIED, IN_SMTLIB, IN_SMTLIB_2, IN_DATALOG, IN_DIMACS, IN_WCNF, IN_OPB, IN_Z3_LOG } input_kind;
+typedef enum { IN_UNSPECIFIED, IN_SMTLIB, IN_SMTLIB_2, IN_DATALOG, IN_DIMACS, IN_WCNF, IN_OPB, IN_Z3_LOG, IN_MPS } input_kind;
 
 std::string         g_aux_input_file;
 char const *        g_input_file          = 0;
@@ -342,6 +343,10 @@ int STD_CALL main(int argc, char ** argv) {
                 else if (strcmp(ext, "smt") == 0) {
                     g_input_kind = IN_SMTLIB;
                 }
+                else if (strcmp(ext, "mps") == 0 || strcmp(ext, "sif") == 0 ||
+                         strcmp(ext, "MPS") == 0 || strcmp(ext, "SIF") == 0) {
+                    g_input_kind = IN_MPS;
+                }
             }
     }
         switch (g_input_kind) {
@@ -367,6 +372,9 @@ int STD_CALL main(int argc, char ** argv) {
         case IN_Z3_LOG:
             replay_z3_log(g_input_file);
             break;
+        case IN_MPS:
+            return_value = read_mps_file(g_input_file);
+            break;
         default:
             UNREACHABLE();
         }

src/smt/params/smt_params.cpp

@@ -32,6 +32,7 @@ void smt_params::updt_local_params(params_ref const & _p) {
     m_restart_factor = p.restart_factor();
     m_case_split_strategy = static_cast<case_split_strategy>(p.case_split());
     m_theory_case_split = p.theory_case_split();
+    m_theory_aware_branching = p.theory_aware_branching();
     m_delay_units = p.delay_units();
     m_delay_units_threshold = p.delay_units_threshold();
     m_preprocess = _p.get_bool("preprocess", true); // hidden parameter

src/smt/params/smt_params.h

@@ -25,6 +25,7 @@ Revision History:
 #include"theory_arith_params.h"
 #include"theory_array_params.h"
 #include"theory_bv_params.h"
+#include"theory_str_params.h"
 #include"theory_pb_params.h"
 #include"theory_datatype_params.h"
 #include"preprocessor_params.h"
@@ -76,6 +77,7 @@ struct smt_params : public preprocessor_params,
                     public theory_arith_params, 
                     public theory_array_params, 
                     public theory_bv_params,
+                    public theory_str_params,
                     public theory_pb_params,
                     public theory_datatype_params {
     bool             m_display_proof;
@@ -111,6 +113,7 @@ struct smt_params : public preprocessor_params,
     unsigned            m_rel_case_split_order;
     bool                m_lookahead_diseq;
     bool                m_theory_case_split;
+    bool                m_theory_aware_branching;
 
     // -----------------------------------
     //
@@ -248,6 +251,8 @@ struct smt_params : public preprocessor_params,
         m_case_split_strategy(CS_ACTIVITY_DELAY_NEW),
         m_rel_case_split_order(0),
         m_lookahead_diseq(false),
+        m_theory_case_split(false),
+        m_theory_aware_branching(false),
         m_delay_units(false),
         m_delay_units_threshold(32),
         m_theory_resolve(false),
@@ -290,7 +295,7 @@ struct smt_params : public preprocessor_params,
         m_check_at_labels(false),
         m_dump_goal_as_smt(false),
         m_auto_config(true),
-        m_string_solver(symbol("seq")){
+        m_string_solver(symbol("auto")){
         updt_local_params(p);
     }
 

src/smt/params/smt_params_helper.pyg

@@ -64,6 +64,18 @@ def_module_params(module_name='smt',
                           ('theory_case_split', BOOL, False, 'Allow the context to use heuristics involving theory case splits, which are a set of literals of which exactly one can be assigned True. If this option is false, the context will generate extra axioms to enforce this instead.'),
                           ('string_solver', SYMBOL, 'seq', 'solver for string/sequence theories. options are: \'z3str3\' (specialized string solver), \'seq\' (sequence solver), \'auto\' (use static features to choose best solver)'),
                           ('core.validate', BOOL, False, 'validate unsat core produced by SMT context'),
+                          ('str.strong_arrangements', BOOL, True, 'assert equivalences instead of implications when generating string arrangement axioms'),
+                          ('str.aggressive_length_testing', BOOL, False, 'prioritize testing concrete length values over generating more options'),
+                          ('str.aggressive_value_testing', BOOL, False, 'prioritize testing concrete string constant values over generating more options'),
+                          ('str.aggressive_unroll_testing', BOOL, True, 'prioritize testing concrete regex unroll counts over generating more options'),
+                          ('str.fast_length_tester_cache', BOOL, False, 'cache length tester constants instead of regenerating them'),
+                          ('str.fast_value_tester_cache', BOOL, True, 'cache value tester constants instead of regenerating them'),
+                          ('str.string_constant_cache', BOOL, True, 'cache all generated string constants generated from anywhere in theory_str'),
+                          ('str.use_binary_search', BOOL, False, 'use a binary search heuristic for finding concrete length values for free variables in theory_str (set to False to use linear search)'),
+                          ('str.binary_search_start', UINT, 64, 'initial upper bound for theory_str binary search'),
+                          ('theory_aware_branching', BOOL, False, 'Allow the context to use extra information from theory solvers regarding literal branching prioritization.'),
+                          ('str.finite_overlap_models', BOOL, False, 'attempt a finite model search for overlapping variables instead of completely giving up on the arrangement'),
+                          ('str.overlap_priority', DOUBLE, -0.1, 'theory-aware priority for overlapping variable cases; use smt.theory_aware_branching=true'),
                           ('core.minimize', BOOL, False, 'minimize unsat core produced by SMT context'),
                           ('core.extend_patterns', BOOL, False, 'extend unsat core with literals that trigger (potential) quantifier instances'),
                           ('core.extend_patterns.max_distance', UINT, UINT_MAX, 'limits the distance of a pattern-extended unsat core'),

src/smt/params/theory_str_params.cpp

@@ -0,0 +1,34 @@
+/*++
+Module Name:
+
+    theory_str_params.cpp
+
+Abstract:
+
+    Parameters for string theory plugin
+
+Author:
+
+    Murphy Berzish (mtrberzi) 2016-12-13
+
+Revision History:
+
+--*/
+
+#include"theory_str_params.h"
+#include"smt_params_helper.hpp"
+
+void theory_str_params::updt_params(params_ref const & _p) {
+    smt_params_helper p(_p);
+    m_StrongArrangements = p.str_strong_arrangements();
+    m_AggressiveLengthTesting = p.str_aggressive_length_testing();
+    m_AggressiveValueTesting = p.str_aggressive_value_testing();
+    m_AggressiveUnrollTesting = p.str_aggressive_unroll_testing();
+    m_UseFastLengthTesterCache = p.str_fast_length_tester_cache();
+    m_UseFastValueTesterCache = p.str_fast_value_tester_cache();
+    m_StringConstantCache = p.str_string_constant_cache();
+    m_FiniteOverlapModels = p.str_finite_overlap_models();
+    m_UseBinarySearch = p.str_use_binary_search();
+    m_BinarySearchInitialUpperBound = p.str_binary_search_start();
+    m_OverlapTheoryAwarePriority = p.str_overlap_priority();
+}

src/smt/params/theory_str_params.h

@@ -0,0 +1,102 @@
+/*++
+Module Name:
+
+    theory_str_params.h
+
+Abstract:
+
+    Parameters for string theory plugin
+
+Author:
+
+    Murphy Berzish (mtrberzi) 2016-12-13
+
+Revision History:
+
+--*/
+
+#ifndef THEORY_STR_PARAMS_H
+#define THEORY_STR_PARAMS_H
+
+#include"params.h"
+
+struct theory_str_params {
+    /*
+     * If AssertStrongerArrangements is set to true,
+     * the implications that would normally be asserted during arrangement generation
+     * will instead be asserted as equivalences.
+     * This is a stronger version of the standard axiom.
+     * The Z3str2 axioms can be simulated by setting this to false.
+     */
+    bool m_StrongArrangements;
+
+    /*
+     * If AggressiveLengthTesting is true, we manipulate the phase of length tester equalities
+     * to prioritize trying concrete length options over choosing the "more" option.
+     */
+    bool m_AggressiveLengthTesting;
+
+    /*
+     * Similarly, if AggressiveValueTesting is true, we manipulate the phase of value tester equalities
+     * to prioritize trying concrete value options over choosing the "more" option.
+     */
+    bool m_AggressiveValueTesting;
+
+    /*
+     * If AggressiveUnrollTesting is true, we manipulate the phase of regex unroll tester equalities
+     * to prioritize trying concrete unroll counts over choosing the "more" option.
+     */
+    bool m_AggressiveUnrollTesting;
+
+    /*
+     * If UseFastLengthTesterCache is set to true,
+     * length tester terms will not be generated from scratch each time they are needed,
+     * but will be saved in a map and looked up.
+     */
+    bool m_UseFastLengthTesterCache;
+
+    /*
+     * If UseFastValueTesterCache is set to true,
+     * value tester terms will not be generated from scratch each time they are needed,
+     * but will be saved in a map and looked up.
+     */
+    bool m_UseFastValueTesterCache;
+
+    /*
+     * If StringConstantCache is set to true,
+     * all string constants in theory_str generated from anywhere will be cached and saved.
+     */
+    bool m_StringConstantCache;
+
+    /*
+     * If FiniteOverlapModels is set to true,
+     * arrangements that result in overlapping variables will generate a small number of models
+     * to test instead of completely giving up on the case.
+     */
+    bool m_FiniteOverlapModels;
+
+    bool m_UseBinarySearch;
+    unsigned m_BinarySearchInitialUpperBound;
+
+    double m_OverlapTheoryAwarePriority;
+
+    theory_str_params(params_ref const & p = params_ref()):
+        m_StrongArrangements(true),
+        m_AggressiveLengthTesting(false),
+        m_AggressiveValueTesting(false),
+        m_AggressiveUnrollTesting(true),
+        m_UseFastLengthTesterCache(false),
+        m_UseFastValueTesterCache(true),
+        m_StringConstantCache(true),
+        m_FiniteOverlapModels(false),
+        m_UseBinarySearch(false),
+        m_BinarySearchInitialUpperBound(64),
+        m_OverlapTheoryAwarePriority(-0.1)
+    {
+        updt_params(p);
+    }
+
+    void updt_params(params_ref const & p);
+};
+
+#endif /* THEORY_STR_PARAMS_H */

src/smt/smt_context.cpp

@@ -2448,8 +2448,9 @@ namespace smt {
         
         ptr_vector<theory>::iterator it  = m_theory_set.begin();
         ptr_vector<theory>::iterator end = m_theory_set.end();
-        for (; it != end; ++it)
+        for (; it != end; ++it) {
             (*it)->pop_scope_eh(num_scopes);
+        }
 
         del_justifications(m_justifications, s.m_justifications_lim);
 
@@ -3013,6 +3014,10 @@ namespace smt {
         }
     }
 
+    void context::add_theory_aware_branching_info(bool_var v, double priority, lbool phase) {
+        m_case_split_queue->add_theory_aware_branching_info(v, priority, phase);
+    }
+
     void context::undo_th_case_split(literal l) {
         m_all_th_case_split_literals.remove(l.index());
         if (m_literal2casesplitsets.contains(l.index())) {
@@ -3022,10 +3027,6 @@ namespace smt {
         }
     }
 
-    void context::add_theory_aware_branching_info(bool_var v, double priority, lbool phase) {
-        m_case_split_queue->add_theory_aware_branching_info(v, priority, phase);
-    }
-
     bool context::propagate_th_case_split(unsigned qhead) {
         if (m_all_th_case_split_literals.empty())
             return true;
@@ -3034,7 +3035,7 @@ namespace smt {
         // not counting any literals that get assigned by this method
         // this relies on bcp() to give us its old m_qhead and therefore
         // bcp() should always be called before this method
-
+	
         unsigned assigned_literal_end = m_assigned_literals.size();
         for (; qhead < assigned_literal_end; ++qhead) {
             literal l = m_assigned_literals[qhead];
@@ -3114,11 +3115,18 @@ namespace smt {
     }
 
     bool is_valid_assumption(ast_manager & m, expr * assumption) {
+        expr* arg;
         if (!m.is_bool(assumption))
             return false;
         if (is_uninterp_const(assumption))
             return true;
-        if (m.is_not(assumption) && is_uninterp_const(to_app(assumption)->get_arg(0)))
+        if (m.is_not(assumption, arg) && is_uninterp_const(arg))
+            return true;
+        if (!is_app(assumption)) 
+            return false;
+        if (to_app(assumption)->get_num_args() == 0)
+            return true;
+        if (m.is_not(assumption, arg) && is_app(arg) && to_app(arg)->get_num_args() == 0)
             return true;
         return false;
     }

src/smt/smt_setup.cpp

@@ -20,6 +20,7 @@ Revision History:
 #include"smt_setup.h"
 #include"static_features.h"
 #include"theory_arith.h"
+#include"theory_lra.h"
 #include"theory_dense_diff_logic.h"
 #include"theory_diff_logic.h"
 #include"theory_utvpi.h"
@@ -33,6 +34,7 @@ Revision History:
 #include"theory_seq.h"
 #include"theory_pb.h"
 #include"theory_fpa.h"
+#include"theory_str.h"
 
 namespace smt {
 
@@ -205,7 +207,7 @@ namespace smt {
     void setup::setup_QF_BVRE() {
         setup_QF_BV();
         setup_QF_LIA();
-        setup_seq();
+        m_context.register_plugin(alloc(theory_seq, m_manager));
     }
 
     void setup::setup_QF_UF(static_features const & st) {
@@ -441,7 +443,7 @@ namespace smt {
         m_params.m_arith_propagate_eqs = false;
         m_params.m_eliminate_term_ite  = true;
         m_params.m_nnf_cnf             = false;
-        setup_mi_arith();
+        setup_r_arith();
     }
 
     void setup::setup_QF_LRA(static_features const & st) {
@@ -466,7 +468,7 @@ namespace smt {
             m_params.m_restart_adaptive      = false;
         }
         m_params.m_arith_small_lemma_size = 32;
-        setup_mi_arith();
+        setup_r_arith();
     }
 
     void setup::setup_QF_LIA() {
@@ -538,7 +540,7 @@ namespace smt {
         m_params.m_relevancy_lvl       = 0;
         m_params.m_arith_reflect       = false; 
         m_params.m_nnf_cnf             = false;
-        setup_mi_arith();
+        setup_r_arith();
     }
 
     void setup::setup_QF_BV() {
@@ -705,7 +707,8 @@ namespace smt {
     }
 
     void setup::setup_QF_S() {
-        setup_seq();
+        m_context.register_plugin(alloc(smt::theory_mi_arith, m_manager, m_params));
+        m_context.register_plugin(alloc(smt::theory_str, m_manager, m_params));
     }
 
     bool is_arith(static_features const & st) {
@@ -716,6 +719,13 @@ namespace smt {
         m_context.register_plugin(alloc(smt::theory_i_arith, m_manager, m_params));
     }
 
+    void setup::setup_r_arith() {
+        m_context.register_plugin(alloc(smt::theory_mi_arith, m_manager, m_params));
+        
+        // Disabled in initial commit of LRA additions
+        // m_context.register_plugin(alloc(smt::theory_lra, m_manager, m_params));
+    }
+
     void setup::setup_mi_arith() {
         if (m_params.m_arith_mode == AS_OPTINF) {
             m_context.register_plugin(alloc(smt::theory_inf_arith, m_manager, m_params));            
@@ -853,7 +863,8 @@ namespace smt {
     }
 
     void setup::setup_str() {
-        m_context.register_plugin(alloc(smt::theory_seq, m_manager));
+        setup_arith();
+        m_context.register_plugin(alloc(theory_str, m_manager, m_params));
     }
 
     void setup::setup_seq() {

src/smt/smt_setup.h

@@ -99,6 +99,7 @@ namespace smt {
         void setup_card();
         void setup_i_arith();
         void setup_mi_arith();
+        void setup_r_arith();
         void setup_fpa();
         void setup_str();
 

src/smt/smt_theory.cpp

@@ -54,7 +54,7 @@ namespace smt {
         }
     }
 
-    void theory::display_app(std::ostream & out, app * n) const {
+    std::ostream& theory::display_app(std::ostream & out, app * n) const {
         func_decl * d = n->get_decl();
         if (n->get_num_args() == 0) {
             out << d->get_name();
@@ -73,9 +73,10 @@ namespace smt {
         else {
             out << "#" << n->get_id();
         }
+        return out;
     }
 
-    void theory::display_flat_app(std::ostream & out, app * n) const {
+    std::ostream& theory::display_flat_app(std::ostream & out, app * n) const {
         func_decl * d = n->get_decl();
         if (n->get_num_args() == 0) {
             out << d->get_name();
@@ -106,6 +107,7 @@ namespace smt {
         else {
             out << "#" << n->get_id();
         }
+        return out;
     }
     
     bool theory::is_relevant_and_shared(enode * n) const {

src/smt/smt_theory.h

@@ -186,13 +186,13 @@ namespace smt {
         }
 
         /**
-           \brief This method is called from smt_context when an unsat core is generated.
+           \brief This method is called from the smt_context when an unsat core is generated.
            The theory may change the answer to UNKNOWN by returning l_undef from this method.
         */
         virtual lbool validate_unsat_core(expr_ref_vector & unsat_core) {
             return l_false;
         }
-
+	
         /**
            \brief This method is invoked before the search starts.
         */
@@ -337,14 +337,14 @@ namespace smt {
         
         virtual void collect_statistics(::statistics & st) const {
         }
-
-        void display_app(std::ostream & out, app * n) const;
-
-        void display_flat_app(std::ostream & out, app * n) const;
         
-        void display_var_def(std::ostream & out, theory_var v) const { return display_app(out, get_enode(v)->get_owner()); }
+        std::ostream& display_app(std::ostream & out, app * n) const;
         
-        void display_var_flat_def(std::ostream & out, theory_var v) const { return display_flat_app(out, get_enode(v)->get_owner()); }
+        std::ostream& display_flat_app(std::ostream & out, app * n) const;
+        
+        std::ostream& display_var_def(std::ostream & out, theory_var v) const { return display_app(out, get_enode(v)->get_owner()); }
+        
+        std::ostream& display_var_flat_def(std::ostream & out, theory_var v) const { return display_flat_app(out, get_enode(v)->get_owner());  }
 
         /**
            \brief Assume eqs between variable that are equal with respect to the given table.

src/smt/theory_arith.h

@@ -505,7 +505,7 @@ namespace smt {
         struct var_value_eq {
             theory_arith & m_th;
             var_value_eq(theory_arith & th):m_th(th) {}
-            bool operator()(theory_var v1, theory_var v2) const { return m_th.get_value(v1) == m_th.get_value(v2) && m_th.is_int(v1) == m_th.is_int(v2); }
+            bool operator()(theory_var v1, theory_var v2) const { return m_th.get_value(v1) == m_th.get_value(v2) && m_th.is_int_src(v1) == m_th.is_int_src(v2); }
         };
 
         typedef int_hashtable<var_value_hash, var_value_eq> var_value_table;

src/smt/theory_arith_aux.h

@@ -2201,16 +2201,19 @@ namespace smt {
         int num       = get_num_vars();
         for (theory_var v = 0; v < num; v++) {
             enode * n        = get_enode(v);
-            TRACE("func_interp_bug", tout << "#" << n->get_owner_id() << " -> " << m_value[v] << "\n";);
+            TRACE("func_interp_bug", tout << mk_pp(n->get_owner(), get_manager()) << " -> " << m_value[v] << " root #" << n->get_root()->get_owner_id() << " " << is_relevant_and_shared(n) << "\n";);
-            if (!is_relevant_and_shared(n))
+            if (!is_relevant_and_shared(n)) {
                 continue;
+            }
             theory_var other = null_theory_var;
             other = m_var_value_table.insert_if_not_there(v);
-            if (other == v)
+            if (other == v) {
                 continue;
+            }
             enode * n2 = get_enode(other);
-            if (n->get_root() == n2->get_root())
+            if (n->get_root() == n2->get_root()) {
                 continue;
+            }
             TRACE("func_interp_bug", tout << "adding to assume_eq queue #" << n->get_owner_id() << " #" << n2->get_owner_id() << "\n";);
             m_assume_eq_candidates.push_back(std::make_pair(other, v));
             result = true;

src/smt/theory_lra.h

@@ -0,0 +1,96 @@
+/*++
+Copyright (c) 2016 Microsoft Corporation
+
+Module Name:
+
+    theory_lra.h
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Lev Nachmanson (levnach) 2016-25-3
+    Nikolaj Bjorner (nbjorner)
+
+Revision History:
+
+
+--*/
+#pragma once
+
+#include "theory_opt.h"
+
+namespace smt {
+    class theory_lra : public theory, public theory_opt {
+        class imp;
+        imp* m_imp;
+    public:
+        theory_lra(ast_manager& m, theory_arith_params& params);
+        virtual ~theory_lra();
+        virtual theory* mk_fresh(context* new_ctx);
+        virtual char const* get_name() const { return "lra"; }
+        
+        virtual void init(context * ctx);
+
+        virtual bool internalize_atom(app * atom, bool gate_ctx);
+                                                     
+        virtual bool internalize_term(app * term);
+
+        virtual void internalize_eq_eh(app * atom, bool_var v);
+
+        virtual void assign_eh(bool_var v, bool is_true);
+
+        virtual void new_eq_eh(theory_var v1, theory_var v2);
+
+        virtual bool use_diseqs() const;
+
+        virtual void new_diseq_eh(theory_var v1, theory_var v2);
+
+        virtual void push_scope_eh();
+
+        virtual void pop_scope_eh(unsigned num_scopes);
+
+        virtual void restart_eh();
+
+        virtual void relevant_eh(app* e);
+
+        virtual void init_search_eh();
+
+        virtual final_check_status final_check_eh();
+
+        virtual bool is_shared(theory_var v) const;
+    
+        virtual bool can_propagate();
+        
+        virtual void propagate();
+        
+        virtual justification * why_is_diseq(theory_var v1, theory_var v2);
+
+        // virtual void flush_eh();
+
+        virtual void reset_eh();
+
+        virtual void init_model(model_generator & m);
+        
+        virtual model_value_proc * mk_value(enode * n, model_generator & mg);
+
+        virtual bool get_value(enode* n, expr_ref& r);
+
+        virtual bool validate_eq_in_model(theory_var v1, theory_var v2, bool is_true) const;
+                
+        virtual void display(std::ostream & out) const;
+        
+        virtual void collect_statistics(::statistics & st) const;
+
+        // optimization
+        virtual inf_eps value(theory_var);
+        virtual inf_eps maximize(theory_var v, expr_ref& blocker, bool& has_shared); 
+        virtual theory_var add_objective(app* term);
+        virtual expr_ref mk_ge(filter_model_converter& fm, theory_var v, inf_rational const& val);
+
+
+    };
+
+}

src/smt/theory_str.h

@@ -0,0 +1,653 @@
+/*++
+  Module Name:
+
+  theory_str.h
+
+  Abstract:
+
+  String Theory Plugin
+
+  Author:
+
+  Murphy Berzish and Yunhui Zheng
+
+  Revision History:
+
+  --*/
+#ifndef _THEORY_STR_H_
+#define _THEORY_STR_H_
+
+#include"smt_theory.h"
+#include"theory_str_params.h"
+#include"trail.h"
+#include"th_rewriter.h"
+#include"value_factory.h"
+#include"smt_model_generator.h"
+#include"arith_decl_plugin.h"
+#include<set>
+#include<stack>
+#include<vector>
+#include<map>
+#include"seq_decl_plugin.h"
+#include"union_find.h"
+
+namespace smt {
+
+typedef hashtable<symbol, symbol_hash_proc, symbol_eq_proc> symbol_set;
+
+class str_value_factory : public value_factory {
+    seq_util u;
+    symbol_set m_strings;
+    std::string delim;
+    unsigned m_next;
+public:
+    str_value_factory(ast_manager & m, family_id fid) :
+        value_factory(m, fid),
+        u(m), delim("!"), m_next(0) {}
+    virtual ~str_value_factory() {}
+    virtual expr * get_some_value(sort * s) {
+        return u.str.mk_string(symbol("some value"));
+    }
+    virtual bool get_some_values(sort * s, expr_ref & v1, expr_ref & v2) {
+        v1 = u.str.mk_string(symbol("value 1"));
+        v2 = u.str.mk_string(symbol("value 2"));
+        return true;
+    }
+    virtual expr * get_fresh_value(sort * s) {
+        if (u.is_string(s)) {
+            while (true) {
+                std::ostringstream strm;
+                strm << delim << std::hex << (m_next++) << std::dec << delim;
+                symbol sym(strm.str().c_str());
+                if (m_strings.contains(sym)) continue;
+                m_strings.insert(sym);
+                return u.str.mk_string(sym);
+            }
+        }
+        sort* seq = 0;
+        if (u.is_re(s, seq)) {
+            expr* v0 = get_fresh_value(seq);
+            return u.re.mk_to_re(v0);
+        }
+        TRACE("t_str", tout << "unexpected sort in get_fresh_value(): " << mk_pp(s, m_manager) << std::endl;);
+        UNREACHABLE(); return NULL;
+    }
+    virtual void register_value(expr * n) { /* Ignore */ }
+};
+
+// rather than modify obj_pair_map I inherit from it and add my own helper methods
+class theory_str_contain_pair_bool_map_t : public obj_pair_map<expr, expr, expr*> {
+public:
+    expr * operator[](std::pair<expr*, expr*> key) const {
+        expr * value;
+        bool found = this->find(key.first, key.second, value);
+        if (found) {
+            return value;
+        } else {
+            TRACE("t_str", tout << "WARNING: lookup miss in contain_pair_bool_map!" << std::endl;);
+            return NULL;
+        }
+    }
+
+    bool contains(std::pair<expr*, expr*> key) const {
+        expr * unused;
+        return this->find(key.first, key.second, unused);
+    }
+};
+
+template<typename Ctx>
+class binary_search_trail : public trail<Ctx> {
+    obj_map<expr, ptr_vector<expr> > & target;
+    expr * entry;
+public:
+    binary_search_trail(obj_map<expr, ptr_vector<expr> > & target, expr * entry) :
+        target(target), entry(entry) {}
+    virtual ~binary_search_trail() {}
+    virtual void undo(Ctx & ctx) {
+        TRACE("t_str_binary_search", tout << "in binary_search_trail::undo()" << std::endl;);
+        if (target.contains(entry)) {
+            if (!target[entry].empty()) {
+                target[entry].pop_back();
+            } else {
+                TRACE("t_str_binary_search", tout << "WARNING: attempt to remove length tester from an empty stack" << std::endl;);
+            }
+        } else {
+            TRACE("t_str_binary_search", tout << "WARNING: attempt to access length tester map via invalid key" << std::endl;);
+        }
+    }
+};
+
+
+class nfa {
+protected:
+    bool m_valid;
+    unsigned m_next_id;
+
+    unsigned next_id() {
+        unsigned retval = m_next_id;
+        ++m_next_id;
+        return retval;
+    }
+
+    unsigned m_start_state;
+    unsigned m_end_state;
+
+    std::map<unsigned, std::map<char, unsigned> > transition_map;
+    std::map<unsigned, std::set<unsigned> > epsilon_map;
+
+    void make_transition(unsigned start, char symbol, unsigned end) {
+        transition_map[start][symbol] = end;
+    }
+
+    void make_epsilon_move(unsigned start, unsigned end) {
+        epsilon_map[start].insert(end);
+    }
+
+    // Convert a regular expression to an e-NFA using Thompson's construction
+    void convert_re(expr * e, unsigned & start, unsigned & end, seq_util & u);
+
+public:
+    nfa(seq_util & u, expr * e)
+: m_valid(true), m_next_id(0), m_start_state(0), m_end_state(0) {
+        convert_re(e, m_start_state, m_end_state, u);
+    }
+
+    nfa() : m_valid(false), m_next_id(0), m_start_state(0), m_end_state(0) {}
+
+    bool is_valid() const {
+        return m_valid;
+    }
+
+    void epsilon_closure(unsigned start, std::set<unsigned> & closure);
+
+    bool matches(zstring input);
+};
+
+class theory_str : public theory {
+    struct T_cut
+    {
+        int level;
+        std::map<expr*, int> vars;
+
+        T_cut() {
+            level = -100;
+        }
+    };
+
+    typedef trail_stack<theory_str> th_trail_stack;
+    typedef union_find<theory_str> th_union_find;
+
+    typedef map<rational, expr*, obj_hash<rational>, default_eq<rational> > rational_map;
+    struct zstring_hash_proc {
+        unsigned operator()(zstring const & s) const {
+            return string_hash(s.encode().c_str(), static_cast<unsigned>(s.length()), 17);
+        }
+    };
+    typedef map<zstring, expr*, zstring_hash_proc, default_eq<zstring> > string_map;
+
+protected:
+    theory_str_params const & m_params;
+
+    /*
+     * Setting EagerStringConstantLengthAssertions to true allows some methods,
+     * in particular internalize_term(), to add
+     * length assertions about relevant string constants.
+     * Note that currently this should always be set to 'true', or else *no* length assertions
+     * will be made about string constants.
+     */
+    bool opt_EagerStringConstantLengthAssertions;
+
+    /*
+     * If VerifyFinalCheckProgress is set to true, continuing after final check is invoked
+     * without asserting any new axioms is considered a bug and will throw an exception.
+     */
+    bool opt_VerifyFinalCheckProgress;
+
+    /*
+     * This constant controls how eagerly we expand unrolls in unbounded regex membership tests.
+     */
+    int opt_LCMUnrollStep;
+
+    /*
+     * If NoQuickReturn_IntegerTheory is set to true,
+     * integer theory integration checks that assert axioms
+     * will not return from the function after asserting their axioms.
+     * The default behaviour of Z3str2 is to set this to 'false'. This may be incorrect.
+     */
+    bool opt_NoQuickReturn_IntegerTheory;
+
+    /*
+     * If DisableIntegerTheoryIntegration is set to true,
+     * ALL calls to the integer theory integration methods
+     * (get_value, get_len_value, lower_bound, upper_bound)
+     * will ignore what the arithmetic solver believes about length terms,
+     * and will return no information.
+     *
+     * This reduces performance significantly, but can be useful to enable
+     * if it is suspected that string-integer integration, or the arithmetic solver itself,
+     * might have a bug.
+     *
+     * The default behaviour of Z3str2 is to set this to 'false'.
+     */
+    bool opt_DisableIntegerTheoryIntegration;
+
+    /*
+     * If DeferEQCConsistencyCheck is set to true,
+     * expensive calls to new_eq_check() will be deferred until final check,
+     * at which time the consistency of *all* string equivalence classes will be validated.
+     */
+    bool opt_DeferEQCConsistencyCheck;
+
+    /*
+     * If CheckVariableScope is set to true,
+     * pop_scope_eh() and final_check_eh() will run extra checks
+     * to determine whether the current assignment
+     * contains references to any internal variables that are no longer in scope.
+     */
+    bool opt_CheckVariableScope;
+
+    /*
+     * If ConcatOverlapAvoid is set to true,
+     * the check to simplify Concat = Concat in handle_equality() will
+     * avoid simplifying wrt. pairs of Concat terms that will immediately
+     * result in an overlap. (false = Z3str2 behaviour)
+     */
+    bool opt_ConcatOverlapAvoid;
+
+    bool search_started;
+    arith_util m_autil;
+    seq_util u;
+    int sLevel;
+
+    bool finalCheckProgressIndicator;
+
+    expr_ref_vector m_trail; // trail for generated terms
+
+    str_value_factory * m_factory;
+
+    // terms we couldn't go through set_up_axioms() with because they weren't internalized
+    expr_ref_vector m_delayed_axiom_setup_terms;
+
+    ptr_vector<enode> m_basicstr_axiom_todo;
+    svector<std::pair<enode*,enode*> > m_str_eq_todo;
+    ptr_vector<enode> m_concat_axiom_todo;
+    ptr_vector<enode> m_string_constant_length_todo;
+    ptr_vector<enode> m_concat_eval_todo;
+
+    // enode lists for library-aware/high-level string terms (e.g. substr, contains)
+    ptr_vector<enode> m_library_aware_axiom_todo;
+
+    // hashtable of all exprs for which we've already set up term-specific axioms --
+    // this prevents infinite recursive descent with respect to axioms that
+    // include an occurrence of the term for which axioms are being generated
+    obj_hashtable<expr> axiomatized_terms;
+
+    int tmpStringVarCount;
+    int tmpXorVarCount;
+    int tmpLenTestVarCount;
+    int tmpValTestVarCount;
+    std::map<std::pair<expr*, expr*>, std::map<int, expr*> > varForBreakConcat;
+
+    bool avoidLoopCut;
+    bool loopDetected;
+    obj_map<expr, std::stack<T_cut*> > cut_var_map;
+    expr_ref m_theoryStrOverlapAssumption_term;
+
+    obj_hashtable<expr> variable_set;
+    obj_hashtable<expr> internal_variable_set;
+    obj_hashtable<expr> regex_variable_set;
+    std::map<int, std::set<expr*> > internal_variable_scope_levels;
+
+    obj_hashtable<expr> internal_lenTest_vars;
+    obj_hashtable<expr> internal_valTest_vars;
+    obj_hashtable<expr> internal_unrollTest_vars;
+
+    obj_hashtable<expr> input_var_in_len;
+
+    obj_map<expr, unsigned int> fvar_len_count_map;
+    std::map<expr*, ptr_vector<expr> > fvar_lenTester_map;
+    obj_map<expr, expr*> lenTester_fvar_map;
+
+    std::map<expr*, std::map<int, svector<std::pair<int, expr*> > > > fvar_valueTester_map;
+    std::map<expr*, expr*> valueTester_fvar_map;
+
+    std::map<expr*, int_vector> val_range_map;
+
+    // This can't be an expr_ref_vector because the constructor is wrong,
+    // we would need to modify the allocator so we pass in ast_manager
+    std::map<expr*, std::map<std::set<expr*>, ptr_vector<expr> > > unroll_tries_map;
+    std::map<expr*, expr*> unroll_var_map;
+    std::map<std::pair<expr*, expr*>, expr*> concat_eq_unroll_ast_map;
+
+    expr_ref_vector contains_map;
+
+    theory_str_contain_pair_bool_map_t contain_pair_bool_map;
+    //obj_map<expr, obj_pair_set<expr, expr> > contain_pair_idx_map;
+    std::map<expr*, std::set<std::pair<expr*, expr*> > > contain_pair_idx_map;
+
+    std::map<std::pair<expr*, zstring>, expr*> regex_in_bool_map;
+    std::map<expr*, std::set<zstring> > regex_in_var_reg_str_map;
+
+    std::map<expr*, nfa> regex_nfa_cache; // Regex term --> NFA
+
+    char * char_set;
+    std::map<char, int> charSetLookupTable;
+    int charSetSize;
+
+    obj_pair_map<expr, expr, expr*> concat_astNode_map;
+
+    // all (str.to-int) and (int.to-str) terms
+    expr_ref_vector string_int_conversion_terms;
+    obj_hashtable<expr> string_int_axioms;
+
+    // used when opt_FastLengthTesterCache is true
+    rational_map lengthTesterCache;
+    // used when opt_FastValueTesterCache is true
+    string_map valueTesterCache;
+
+    string_map stringConstantCache;
+    unsigned long totalCacheAccessCount;
+    unsigned long cacheHitCount;
+    unsigned long cacheMissCount;
+
+    // cache mapping each string S to Length(S)
+    obj_map<expr, app*> length_ast_map;
+
+    th_union_find m_find;
+    th_trail_stack m_trail_stack;
+    theory_var get_var(expr * n) const;
+    expr * get_eqc_next(expr * n);
+    app * get_ast(theory_var i);
+
+    // binary search heuristic data
+    struct binary_search_info {
+        rational lowerBound;
+        rational midPoint;
+        rational upperBound;
+        rational windowSize;
+
+        binary_search_info() : lowerBound(rational::zero()), midPoint(rational::zero()),
+                upperBound(rational::zero()), windowSize(rational::zero()) {}
+        binary_search_info(rational lower, rational mid, rational upper, rational windowSize) :
+            lowerBound(lower), midPoint(mid), upperBound(upper), windowSize(windowSize) {}
+
+        void calculate_midpoint() {
+            midPoint = floor(lowerBound + ((upperBound - lowerBound) / rational(2)) );
+        }
+    };
+    // maps a free string var to a stack of active length testers.
+    // can use binary_search_trail to record changes to this object
+    obj_map<expr, ptr_vector<expr> > binary_search_len_tester_stack;
+    // maps a length tester var to the *active* search window
+    obj_map<expr, binary_search_info> binary_search_len_tester_info;
+    // maps a free string var to the first length tester to be (re)used
+    obj_map<expr, expr*> binary_search_starting_len_tester;
+    // maps a length tester to the next length tester to be (re)used if the split is "low"
+    obj_map<expr, expr*> binary_search_next_var_low;
+    // maps a length tester to the next length tester to be (re)used if the split is "high"
+    obj_map<expr, expr*> binary_search_next_var_high;
+
+    // finite model finding data
+    // maps a finite model tester var to a list of variables that will be tested
+    obj_map<expr, ptr_vector<expr> > finite_model_test_varlists;
+protected:
+    void assert_axiom(expr * e);
+    void assert_implication(expr * premise, expr * conclusion);
+    expr * rewrite_implication(expr * premise, expr * conclusion);
+
+    expr * mk_string(zstring const& str);
+    expr * mk_string(const char * str);
+
+    app * mk_strlen(expr * e);
+    expr * mk_concat(expr * n1, expr * n2);
+    expr * mk_concat_const_str(expr * n1, expr * n2);
+    app * mk_contains(expr * haystack, expr * needle);
+    app * mk_indexof(expr * haystack, expr * needle);
+    app * mk_fresh_const(char const* name, sort* s);
+
+    literal mk_literal(expr* _e);
+    app * mk_int(int n);
+    app * mk_int(rational & q);
+
+    void check_and_init_cut_var(expr * node);
+    void add_cut_info_one_node(expr * baseNode, int slevel, expr * node);
+    void add_cut_info_merge(expr * destNode, int slevel, expr * srcNode);
+    bool has_self_cut(expr * n1, expr * n2);
+
+    // for ConcatOverlapAvoid
+    bool will_result_in_overlap(expr * lhs, expr * rhs);
+
+    void track_variable_scope(expr * var);
+    app * mk_str_var(std::string name);
+    app * mk_int_var(std::string name);
+    app * mk_nonempty_str_var();
+    app * mk_internal_xor_var();
+    expr * mk_internal_valTest_var(expr * node, int len, int vTries);
+    app * mk_regex_rep_var();
+    app * mk_unroll_bound_var();
+    app * mk_unroll_test_var();
+    void add_nonempty_constraint(expr * s);
+
+    void instantiate_concat_axiom(enode * cat);
+    void try_eval_concat(enode * cat);
+    void instantiate_basic_string_axioms(enode * str);
+    void instantiate_str_eq_length_axiom(enode * lhs, enode * rhs);
+
+    void instantiate_axiom_CharAt(enode * e);
+    void instantiate_axiom_prefixof(enode * e);
+    void instantiate_axiom_suffixof(enode * e);
+    void instantiate_axiom_Contains(enode * e);
+    void instantiate_axiom_Indexof(enode * e);
+    void instantiate_axiom_Indexof2(enode * e);
+    void instantiate_axiom_LastIndexof(enode * e);
+    void instantiate_axiom_Substr(enode * e);
+    void instantiate_axiom_Replace(enode * e);
+    void instantiate_axiom_str_to_int(enode * e);
+    void instantiate_axiom_int_to_str(enode * e);
+
+    expr * mk_RegexIn(expr * str, expr * regexp);
+    void instantiate_axiom_RegexIn(enode * e);
+    app * mk_unroll(expr * n, expr * bound);
+
+    void process_unroll_eq_const_str(expr * unrollFunc, expr * constStr);
+    void unroll_str2reg_constStr(expr * unrollFunc, expr * eqConstStr);
+    void process_concat_eq_unroll(expr * concat, expr * unroll);
+
+    void set_up_axioms(expr * ex);
+    void handle_equality(expr * lhs, expr * rhs);
+
+    app * mk_value_helper(app * n);
+    expr * get_eqc_value(expr * n, bool & hasEqcValue);
+    expr * z3str2_get_eqc_value(expr * n , bool & hasEqcValue);
+    bool in_same_eqc(expr * n1, expr * n2);
+    expr * collect_eq_nodes(expr * n, expr_ref_vector & eqcSet);
+
+    bool get_value(expr* e, rational& val) const;
+    bool get_len_value(expr* e, rational& val);
+    bool lower_bound(expr* _e, rational& lo);
+    bool upper_bound(expr* _e, rational& hi);
+
+    bool can_two_nodes_eq(expr * n1, expr * n2);
+    bool can_concat_eq_str(expr * concat, zstring& str);
+    bool can_concat_eq_concat(expr * concat1, expr * concat2);
+    bool check_concat_len_in_eqc(expr * concat);
+    bool check_length_consistency(expr * n1, expr * n2);
+    bool check_length_const_string(expr * n1, expr * constStr);
+    bool check_length_eq_var_concat(expr * n1, expr * n2);
+    bool check_length_concat_concat(expr * n1, expr * n2);
+    bool check_length_concat_var(expr * concat, expr * var);
+    bool check_length_var_var(expr * var1, expr * var2);
+    void check_contain_in_new_eq(expr * n1, expr * n2);
+    void check_contain_by_eqc_val(expr * varNode, expr * constNode);
+    void check_contain_by_substr(expr * varNode, expr_ref_vector & willEqClass);
+    void check_contain_by_eq_nodes(expr * n1, expr * n2);
+    bool in_contain_idx_map(expr * n);
+    void compute_contains(std::map<expr*, expr*> & varAliasMap,
+            std::map<expr*, expr*> & concatAliasMap, std::map<expr*, expr *> & varConstMap,
+            std::map<expr*, expr*> & concatConstMap, std::map<expr*, std::map<expr*, int> > & varEqConcatMap);
+    expr * dealias_node(expr * node, std::map<expr*, expr*> & varAliasMap, std::map<expr*, expr*> & concatAliasMap);
+    void get_grounded_concats(expr* node, std::map<expr*, expr*> & varAliasMap,
+            std::map<expr*, expr*> & concatAliasMap, std::map<expr*, expr*> & varConstMap,
+            std::map<expr*, expr*> & concatConstMap, std::map<expr*, std::map<expr*, int> > & varEqConcatMap,
+            std::map<expr*, std::map<std::vector<expr*>, std::set<expr*> > > & groundedMap);
+    void print_grounded_concat(expr * node, std::map<expr*, std::map<std::vector<expr*>, std::set<expr*> > > & groundedMap);
+    void check_subsequence(expr* str, expr* strDeAlias, expr* subStr, expr* subStrDeAlias, expr* boolVar,
+            std::map<expr*, std::map<std::vector<expr*>, std::set<expr*> > > & groundedMap);
+    bool is_partial_in_grounded_concat(const std::vector<expr*> & strVec, const std::vector<expr*> & subStrVec);
+
+    void get_nodes_in_concat(expr * node, ptr_vector<expr> & nodeList);
+    expr * simplify_concat(expr * node);
+
+    void simplify_parent(expr * nn, expr * eq_str);
+
+    void simplify_concat_equality(expr * lhs, expr * rhs);
+    void solve_concat_eq_str(expr * concat, expr * str);
+
+    void infer_len_concat_equality(expr * nn1, expr * nn2);
+    bool infer_len_concat(expr * n, rational & nLen);
+    void infer_len_concat_arg(expr * n, rational len);
+
+    bool is_concat_eq_type1(expr * concatAst1, expr * concatAst2);
+    bool is_concat_eq_type2(expr * concatAst1, expr * concatAst2);
+    bool is_concat_eq_type3(expr * concatAst1, expr * concatAst2);
+    bool is_concat_eq_type4(expr * concatAst1, expr * concatAst2);
+    bool is_concat_eq_type5(expr * concatAst1, expr * concatAst2);
+    bool is_concat_eq_type6(expr * concatAst1, expr * concatAst2);
+
+    void process_concat_eq_type1(expr * concatAst1, expr * concatAst2);
+    void process_concat_eq_type2(expr * concatAst1, expr * concatAst2);
+    void process_concat_eq_type3(expr * concatAst1, expr * concatAst2);
+    void process_concat_eq_type4(expr * concatAst1, expr * concatAst2);
+    void process_concat_eq_type5(expr * concatAst1, expr * concatAst2);
+    void process_concat_eq_type6(expr * concatAst1, expr * concatAst2);
+
+    void print_cut_var(expr * node, std::ofstream & xout);
+
+    void generate_mutual_exclusion(expr_ref_vector & exprs);
+    void add_theory_aware_branching_info(expr * term, double priority, lbool phase);
+
+    bool new_eq_check(expr * lhs, expr * rhs);
+    void group_terms_by_eqc(expr * n, std::set<expr*> & concats, std::set<expr*> & vars, std::set<expr*> & consts);
+
+    int ctx_dep_analysis(std::map<expr*, int> & strVarMap, std::map<expr*, int> & freeVarMap,
+            std::map<expr*, std::set<expr*> > & unrollGroupMap, std::map<expr*, std::map<expr*, int> > & var_eq_concat_map);
+    void trace_ctx_dep(std::ofstream & tout,
+            std::map<expr*, expr*> & aliasIndexMap,
+            std::map<expr*, expr*> & var_eq_constStr_map,
+            std::map<expr*, std::map<expr*, int> > & var_eq_concat_map,
+            std::map<expr*, std::map<expr*, int> > & var_eq_unroll_map,
+            std::map<expr*, expr*> & concat_eq_constStr_map,
+            std::map<expr*, std::map<expr*, int> > & concat_eq_concat_map,
+            std::map<expr*, std::set<expr*> > & unrollGroupMap);
+
+    void classify_ast_by_type(expr * node, std::map<expr*, int> & varMap,
+            std::map<expr*, int> & concatMap, std::map<expr*, int> & unrollMap);
+    void classify_ast_by_type_in_positive_context(std::map<expr*, int> & varMap,
+            std::map<expr*, int> & concatMap, std::map<expr*, int> & unrollMap);
+
+    expr * mk_internal_lenTest_var(expr * node, int lTries);
+    expr * gen_len_val_options_for_free_var(expr * freeVar, expr * lenTesterInCbEq, zstring lenTesterValue);
+    void process_free_var(std::map<expr*, int> & freeVar_map);
+    expr * gen_len_test_options(expr * freeVar, expr * indicator, int tries);
+    expr * gen_free_var_options(expr * freeVar, expr * len_indicator,
+            zstring len_valueStr, expr * valTesterInCbEq, zstring valTesterValueStr);
+    expr * gen_val_options(expr * freeVar, expr * len_indicator, expr * val_indicator,
+            zstring lenStr, int tries);
+    void print_value_tester_list(svector<std::pair<int, expr*> > & testerList);
+    bool get_next_val_encode(int_vector & base, int_vector & next);
+    zstring gen_val_string(int len, int_vector & encoding);
+
+    // binary search heuristic
+    expr * binary_search_length_test(expr * freeVar, expr * previousLenTester, zstring previousLenTesterValue);
+    expr_ref binary_search_case_split(expr * freeVar, expr * tester, binary_search_info & bounds, literal_vector & case_split_lits);
+
+    bool free_var_attempt(expr * nn1, expr * nn2);
+    void more_len_tests(expr * lenTester, zstring lenTesterValue);
+    void more_value_tests(expr * valTester, zstring valTesterValue);
+
+    expr * get_alias_index_ast(std::map<expr*, expr*> & aliasIndexMap, expr * node);
+    expr * getMostLeftNodeInConcat(expr * node);
+    expr * getMostRightNodeInConcat(expr * node);
+    void get_var_in_eqc(expr * n, std::set<expr*> & varSet);
+    void get_concats_in_eqc(expr * n, std::set<expr*> & concats);
+    void get_const_str_asts_in_node(expr * node, expr_ref_vector & constList);
+    expr * eval_concat(expr * n1, expr * n2);
+
+    bool finalcheck_str2int(app * a);
+    bool finalcheck_int2str(app * a);
+
+    // strRegex
+
+    void get_eqc_allUnroll(expr * n, expr * &constStr, std::set<expr*> & unrollFuncSet);
+    void get_eqc_simpleUnroll(expr * n, expr * &constStr, std::set<expr*> & unrollFuncSet);
+    void gen_assign_unroll_reg(std::set<expr*> & unrolls);
+    expr * gen_assign_unroll_Str2Reg(expr * n, std::set<expr*> & unrolls);
+    expr * gen_unroll_conditional_options(expr * var, std::set<expr*> & unrolls, zstring lcmStr);
+    expr * gen_unroll_assign(expr * var, zstring lcmStr, expr * testerVar, int l, int h);
+    void reduce_virtual_regex_in(expr * var, expr * regex, expr_ref_vector & items);
+    void check_regex_in(expr * nn1, expr * nn2);
+    zstring get_std_regex_str(expr * r);
+
+    void dump_assignments();
+    void initialize_charset();
+
+    void check_variable_scope();
+    void recursive_check_variable_scope(expr * ex);
+
+    void collect_var_concat(expr * node, std::set<expr*> & varSet, std::set<expr*> & concatSet);
+    bool propagate_length(std::set<expr*> & varSet, std::set<expr*> & concatSet, std::map<expr*, int> & exprLenMap);
+    void get_unique_non_concat_nodes(expr * node, std::set<expr*> & argSet);
+    bool propagate_length_within_eqc(expr * var);
+
+    // TESTING
+    void refresh_theory_var(expr * e);
+
+    expr_ref set_up_finite_model_test(expr * lhs, expr * rhs);
+    void finite_model_test(expr * v, expr * c);
+
+public:
+    theory_str(ast_manager & m, theory_str_params const & params);
+    virtual ~theory_str();
+
+    virtual char const * get_name() const { return "seq"; }
+    virtual void display(std::ostream & out) const;
+
+    bool overlapping_variables_detected() const { return loopDetected; }
+
+    th_trail_stack& get_trail_stack() { return m_trail_stack; }
+    void merge_eh(theory_var, theory_var, theory_var v1, theory_var v2) {}
+    void after_merge_eh(theory_var r1, theory_var r2, theory_var v1, theory_var v2) { }
+    void unmerge_eh(theory_var v1, theory_var v2) {}
+protected:
+    virtual bool internalize_atom(app * atom, bool gate_ctx);
+    virtual bool internalize_term(app * term);
+    virtual enode* ensure_enode(expr* e);
+    virtual theory_var mk_var(enode * n);
+
+    virtual void new_eq_eh(theory_var, theory_var);
+    virtual void new_diseq_eh(theory_var, theory_var);
+
+    virtual theory* mk_fresh(context*) { return alloc(theory_str, get_manager(), m_params); }
+    virtual void init_search_eh();
+    virtual void add_theory_assumptions(expr_ref_vector & assumptions);
+    virtual lbool validate_unsat_core(expr_ref_vector & unsat_core);
+    virtual void relevant_eh(app * n);
+    virtual void assign_eh(bool_var v, bool is_true);
+    virtual void push_scope_eh();
+    virtual void pop_scope_eh(unsigned num_scopes);
+    virtual void reset_eh();
+
+    virtual bool can_propagate();
+    virtual void propagate();
+
+    virtual final_check_status final_check_eh();
+    virtual void attach_new_th_var(enode * n);
+
+    virtual void init_model(model_generator & m);
+    virtual model_value_proc * mk_value(enode * n, model_generator & mg);
+    virtual void finalize_model(model_generator & mg);
+};
+
+};
+
+#endif /* _THEORY_STR_H_ */

src/test/argument_parser.h

@@ -0,0 +1,144 @@
+/*
+Copyright (c) 2013 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Lev Nachmanson
+*/
+
+#include <unordered_map>
+#include <vector>
+#include <string>
+#include <set>
+#include <iostream>
+
+namespace lean {
+class argument_parser {
+    std::unordered_map<std::string, std::string> m_options;
+    std::unordered_map<std::string, std::string> m_options_with_after_string;
+    std::set<std::string> m_used_options;
+    std::unordered_map<std::string, std::string> m_used_options_with_after_string;
+    std::vector<std::string> m_free_args;
+    std::vector<std::string> m_args;
+
+public:
+    std::string m_error_message;
+    argument_parser(unsigned argn, char * const* args) {
+        for (unsigned i = 0; i < argn; i++) {
+            m_args.push_back(std::string(args[i]));
+        }
+    }
+
+    void add_option(std::string s) {
+        add_option_with_help_string(s, "");
+    }
+
+    void add_option_with_help_string(std::string s, std::string help_string) {
+        m_options[s]=help_string;
+    }
+
+    void add_option_with_after_string(std::string s) {
+        add_option_with_after_string_with_help(s, "");
+    }
+
+    void add_option_with_after_string_with_help(std::string s, std::string help_string) {
+        m_options_with_after_string[s]=help_string;
+    }
+
+
+    bool parse() {
+        bool status_is_ok = true;
+        for (unsigned i = 0; i < m_args.size(); i++) {
+            std::string ar = m_args[i];
+            if (m_options.find(ar) != m_options.end() )
+                m_used_options.insert(ar);
+            else if (m_options_with_after_string.find(ar) != m_options_with_after_string.end()) {
+                if (i == m_args.size() - 1) {
+                    m_error_message = "Argument is missing after "+ar;
+                    return false;
+                }
+                i++;
+                m_used_options_with_after_string[ar] = m_args[i];
+            } else {
+                 if (starts_with(ar, "-") || starts_with(ar, "//")) 
+                     status_is_ok = false;
+
+                m_free_args.push_back(ar);
+            }
+        }
+        return status_is_ok;
+    }
+
+    bool contains(std::unordered_map<std::string, std::string> & m, std::string s) {
+        return m.find(s) != m.end();
+    }
+
+    bool contains(std::set<std::string> & m, std::string s) {
+        return m.find(s) != m.end();
+    }
+
+    bool option_is_used(std::string option) {
+        return contains(m_used_options, option) || contains(m_used_options_with_after_string, option);
+    }
+
+    std::string get_option_value(std::string option) {
+        auto t = m_used_options_with_after_string.find(option);
+        if (t != m_used_options_with_after_string.end()){
+            return t->second;
+        }
+        return std::string();
+    }
+
+    bool starts_with(std::string s, char const * prefix) {
+        return starts_with(s, std::string(prefix));
+    }
+
+    bool starts_with(std::string s, std::string prefix) {
+        return s.substr(0, prefix.size()) == prefix;
+    }
+
+    std::string usage_string() {
+        std::string ret = "";
+        std::vector<std::string> unknown_options;
+        for (auto t : m_free_args) {
+            if (starts_with(t, "-") || starts_with(t, "\\")) {
+                unknown_options.push_back(t);
+            }
+        }
+        if (unknown_options.size()) {
+            ret = "Unknown options:";
+        }
+        for (auto unknownOption : unknown_options) {
+            ret += unknownOption;
+            ret += ",";
+        }
+        ret += "\n";
+        ret += "Usage:\n";
+        for (auto allowed_option : m_options)
+            ret += allowed_option.first + " " + (allowed_option.second.size() == 0 ? std::string("") : std::string("/") + allowed_option.second) + std::string("\n");
+        for (auto s : m_options_with_after_string) {
+            ret += s.first + " " + (s.second.size() == 0? " \"option value\"":("\""+ s.second+"\"")) + "\n";
+        }
+        return ret;
+    }
+
+    void print() {
+        if (m_used_options.size() == 0 && m_used_options_with_after_string.size() == 0 && m_free_args.size() == 0) {
+            std::cout << "no options are given" << std::endl;
+            return;
+        }
+        std::cout << "options are: " << std::endl;
+        for (std::string s : m_used_options) {
+            std::cout << s << std::endl;
+        }
+        for (auto & t : m_used_options_with_after_string) {
+            std::cout << t.first << " " << t.second << std::endl;
+        }
+        if (m_free_args.size() > 0) {
+            std::cout << "free arguments are: "  << std::endl;
+            for (auto & t : m_free_args) {
+                std::cout << t << " " <<  std::endl;
+            }
+        }
+    }
+};
+}

src/test/lp_main.cpp

@@ -0,0 +1,14 @@
+void        gparams_register_modules(){}
+void mem_initialize() {}
+void mem_finalize() {}
+#include "util/rational.h"
+namespace lean {
+void test_lp_local(int argc, char**argv);
+}
+int main(int argn, char**argv){
+    rational::initialize();
+    lean::test_lp_local(argn, argv);
+    rational::finalize();
+    return 0;
+}
+

src/test/main.cpp

@@ -239,6 +239,7 @@ int main(int argc, char ** argv) {
     TST(pdr);
     TST_ARGV(ddnf);
     TST(model_evaluator);
+    TST_ARGV(lp);
     TST(get_consequences);
     TST(pb2bv);
     TST_ARGV(cnf_backbones);

src/test/smt2print_parse.cpp

@@ -13,8 +13,9 @@ Copyright (c) 2015 Microsoft Corporation
 void test_print(Z3_context ctx, Z3_ast a) {
     Z3_set_ast_print_mode(ctx, Z3_PRINT_SMTLIB2_COMPLIANT);
     char const* spec1 = Z3_benchmark_to_smtlib_string(ctx, "test", 0, 0, 0, 0, 0, a);
-    std::cout << spec1 << "\n";
+    std::cout << "spec1: benchmark->string\n" << spec1 << "\n";
 
+    std::cout << "attempting to parse spec1...\n";
     Z3_ast b = 
         Z3_parse_smtlib2_string(ctx, 
                                 spec1,
@@ -24,14 +25,14 @@ void test_print(Z3_context ctx, Z3_ast a) {
                                 0,
                                 0,
                                 0);
-
+    std::cout << "parse successful, converting ast->string\n";
     char const* spec2 = Z3_ast_to_string(ctx, b);
-    std::cout << spec2 << "\n";    
+    std::cout << "spec2: string->ast->string\n" << spec2 << "\n";
 }
 
 void test_parseprint(char const* spec) {
     Z3_context ctx = Z3_mk_context(0);
-    std::cout << spec << "\n";
+    std::cout << "spec:\n" << spec << "\n";
 
     Z3_ast a = 
         Z3_parse_smtlib2_string(ctx, 
@@ -43,8 +44,12 @@ void test_parseprint(char const* spec) {
                                 0,
                                 0);
     
+    std::cout << "done parsing\n";
+
     test_print(ctx, a);
 
+    std::cout << "done printing\n";
+
     Z3_del_context(ctx);
 }
 
@@ -104,6 +109,12 @@ void tst_smt2print_parse() {
 
     test_parseprint(spec5);
 
+    // Test strings
+    char const* spec6 =
+        "(assert (= \"abc\" \"abc\"))";
+
+    test_parseprint(spec6);
+
     // Test ?     
 
 }

src/test/smt_reader.h

@@ -0,0 +1,392 @@
+/*
+  Copyright (c) 2013 Microsoft Corporation. All rights reserved.
+  Released under Apache 2.0 license as described in the file LICENSE.
+
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+
+// reads an MPS file reperesenting a Mixed Integer Program
+#include <string>
+#include <vector>
+#include <unordered_map>
+#include "util/lp/lp_primal_simplex.h"
+#include "util/lp/lp_dual_simplex.h"
+#include "util/lp/lar_solver.h"
+#include <iostream>
+#include <fstream>
+#include <functional>
+#include <algorithm>
+#include "util/lp/mps_reader.h"
+#include "util/lp/ul_pair.h"
+#include "util/lp/lar_constraints.h"
+#include <sstream>
+#include <cstdlib>
+namespace lean {
+
+    template<typename T>
+    T from_string(const std::string& str) {
+        std::istringstream ss(str);
+        T ret;
+        ss >> ret;
+        return ret;
+    }
+
+    class smt_reader {
+    public:
+        struct lisp_elem {
+            std::string m_head;
+            std::vector<lisp_elem> m_elems;
+            void print() {
+                if (m_elems.size()) {
+                    std::cout << '(';
+                    std::cout << m_head << ' ';
+                    for (auto & el : m_elems)
+                        el.print();
+
+                    std::cout << ')';
+                } else {
+                    std::cout << " " << m_head;
+                }
+            }
+            unsigned size() const { return static_cast<unsigned>(m_elems.size()); }
+            bool is_simple() const { return size() == 0; }
+        };
+        struct formula_constraint {
+            lconstraint_kind m_kind;
+            std::vector<std::pair<mpq, std::string>> m_coeffs;
+            mpq m_right_side = numeric_traits<mpq>::zero();
+            void add_pair(mpq c, std::string name) {
+                m_coeffs.push_back(make_pair(c, name));
+            }
+        };
+
+        lisp_elem m_formula_lisp_elem;
+
+        std::unordered_map<std::string, unsigned> m_name_to_var_index;
+        std::vector<formula_constraint> m_constraints;
+        std::string m_file_name;
+        std::ifstream m_file_stream;
+        std::string m_line;
+        bool m_is_OK = true;
+        unsigned m_line_number = 0;
+        smt_reader(std::string file_name): 
+            m_file_name(file_name), m_file_stream(file_name) {
+        }
+
+        void set_error() {
+            std::cout << "setting error" << std::endl;
+            m_is_OK = false;
+        }
+
+        bool is_ok() {
+            return m_is_OK;
+        }
+
+        bool prefix(const char * pr) {
+            return m_line.find(pr) == 0;
+        }
+
+        int first_separator() {
+            unsigned blank_pos = static_cast<unsigned>(m_line.find(' '));
+            unsigned br_pos = static_cast<unsigned>(m_line.find('('));
+            unsigned reverse_br_pos = static_cast<unsigned>(m_line.find(')'));
+            return std::min(blank_pos, std::min(br_pos, reverse_br_pos));
+        }
+
+        void fill_lisp_elem(lisp_elem & lm) {
+            if (m_line[0] == '(')
+                fill_nested_elem(lm);
+            else
+                fill_simple_elem(lm);
+        }
+
+        void fill_simple_elem(lisp_elem & lm) {
+            int separator = first_separator();
+            lean_assert(-1 != separator && separator != 0);
+            lm.m_head = m_line.substr(0, separator);
+            m_line = m_line.substr(separator);
+        }
+
+        void fill_nested_elem(lisp_elem & lm) {
+            lean_assert(m_line[0] == '(');
+            m_line = m_line.substr(1);
+            int separator = first_separator();
+            lm.m_head = m_line.substr(0, separator);
+            m_line = m_line.substr(lm.m_head.size());
+            eat_blanks();
+            while (m_line.size()) {
+                if (m_line[0] == '(') {
+                    lisp_elem el;
+                    fill_nested_elem(el);
+                    lm.m_elems.push_back(el);
+                } else {
+                    if (m_line[0] == ')') {
+                        m_line = m_line.substr(1);
+                        break;
+                    }
+                    lisp_elem el;
+                    fill_simple_elem(el);
+                    lm.m_elems.push_back(el);
+                }
+                eat_blanks();
+            }
+        }
+
+        void eat_blanks() {
+            while (m_line.size()) {
+                if (m_line[0] == ' ')
+                    m_line = m_line.substr(1);
+                else
+                    break;
+            }
+        }
+
+        void fill_formula_elem() {
+            fill_lisp_elem(m_formula_lisp_elem);
+        }
+
+        void parse_line() {
+            if (m_line.find(":formula") == 0) {
+                int first_br = static_cast<int>(m_line.find('('));
+                if (first_br == -1) {
+                    std::cout << "empty formula" << std::endl;
+                    return;
+                }
+                m_line = m_line.substr(first_br);
+                fill_formula_elem();
+            }
+        }
+
+        void set_constraint_kind(formula_constraint & c, lisp_elem & el) {
+            if (el.m_head == "=") {
+                c.m_kind = EQ;
+            } else if (el.m_head == ">=") {
+                c.m_kind = GE;
+            } else if (el.m_head == "<=") {
+                c.m_kind = LE;
+            } else if (el.m_head == ">") {
+                c.m_kind = GT;
+            } else if (el.m_head == "<") {
+                c.m_kind = LT;
+            } else {
+                std::cout << "kind " << el.m_head << " is not supported " << std::endl;
+                set_error();
+            }
+        }
+
+        void adjust_rigth_side(formula_constraint & /* c*/, lisp_elem & /*el*/) {
+            // lean_assert(el.m_head == "0"); // do nothing for the time being
+        }
+
+        void set_constraint_coeffs(formula_constraint & c, lisp_elem & el) {
+            lean_assert(el.m_elems.size() == 2);
+            set_constraint_coeffs_on_coeff_element(c, el.m_elems[0]);
+            adjust_rigth_side(c, el.m_elems[1]);
+        }
+
+
+        bool is_integer(std::string & s) {
+            if (s.size() == 0) return false;
+            return atoi(s.c_str()) != 0 || isdigit(s.c_str()[0]);
+        }
+
+        void add_complex_sum_elem(formula_constraint & c, lisp_elem & el) {
+            if (el.m_head == "*") {
+                add_mult_elem(c, el.m_elems);
+            } else if (el.m_head == "~") {
+                lisp_elem & minel = el.m_elems[0];
+                lean_assert(minel.is_simple());
+                c.m_right_side += mpq(str_to_int(minel.m_head));
+            } else {
+                std::cout << "unexpected input " << el.m_head << std::endl;
+                set_error();
+                return;
+            }
+        }
+
+        std::string get_name(lisp_elem & name) {
+            lean_assert(name.is_simple());
+            lean_assert(!is_integer(name.m_head));
+            return name.m_head;
+        }
+
+
+        void add_mult_elem(formula_constraint & c, std::vector<lisp_elem> & els) {
+            lean_assert(els.size() == 2);
+            mpq coeff = get_coeff(els[0]);
+            std::string col_name = get_name(els[1]);
+            c.add_pair(coeff, col_name);
+        }
+
+        mpq get_coeff(lisp_elem & le) {
+            if (le.is_simple()) {
+                return mpq(str_to_int(le.m_head));
+            } else {
+                lean_assert(le.m_head == "~");
+                lean_assert(le.size() == 1);
+                lisp_elem & el = le.m_elems[0];
+                lean_assert(el.is_simple());
+                return -mpq(str_to_int(el.m_head));
+            }
+        }
+
+        int str_to_int(std::string & s) {
+            lean_assert(is_integer(s));
+            return atoi(s.c_str());
+        }
+
+        void add_sum_elem(formula_constraint & c, lisp_elem & el) {
+            if (el.size()) {
+                add_complex_sum_elem(c, el);
+            } else {
+                lean_assert(is_integer(el.m_head));
+                int v = atoi(el.m_head.c_str());
+                mpq vr(v);
+                c.m_right_side -= vr;
+            }
+        }
+
+        void add_sum(formula_constraint & c, std::vector<lisp_elem> & sum_els) {
+            for (auto & el : sum_els)
+                add_sum_elem(c, el);
+        }
+
+        void set_constraint_coeffs_on_coeff_element(formula_constraint & c, lisp_elem & el) {
+            if (el.m_head == "*") {
+                add_mult_elem(c, el.m_elems);
+            } else if (el.m_head == "+") {
+                add_sum(c, el.m_elems);
+            } else {
+                lean_assert(false); // unexpected input
+            }
+        }
+
+        void create_constraint(lisp_elem & el) {
+            formula_constraint c;
+            set_constraint_kind(c, el);
+            set_constraint_coeffs(c, el);
+            m_constraints.push_back(c);
+        }
+
+        void fill_constraints() {
+            if (m_formula_lisp_elem.m_head != "and") {
+                std::cout << "unexpected top element " << m_formula_lisp_elem.m_head << std::endl;
+                set_error();
+                return;
+            }
+            for (auto & el : m_formula_lisp_elem.m_elems)
+                create_constraint(el);
+        }
+
+        void read() {
+            if (!m_file_stream.is_open()){
+                std::cout << "cannot open file " << m_file_name << std::endl;
+                set_error();
+                return;
+            }
+            while (m_is_OK && getline(m_file_stream, m_line)) {
+                parse_line();
+                m_line_number++;
+            }
+
+            m_file_stream.close();
+            fill_constraints();
+        }
+
+        /*
+        void fill_lar_solver_on_row(row * row, lar_solver *solver)  {
+            if (row->m_name != m_cost_row_name) {
+                lar_constraint c(get_lar_relation_from_row(row->m_type), row->m_right_side);
+                for (auto s : row->m_row_columns) {
+                    var_index i = solver->add_var(s.first);
+                    c.add_variable_to_constraint(i, s.second);
+                }
+                solver->add_constraint(&c);
+            } else {
+                // ignore the cost row
+            }
+        }
+
+
+        void fill_lar_solver_on_rows(lar_solver * solver) {
+            for (auto row_it : m_rows) {
+                fill_lar_solver_on_row(row_it.second, solver);
+            }
+        }
+
+        void create_low_constraint_for_var(column* col, bound * b, lar_solver *solver) {
+            lar_constraint c(GE, b->m_low);
+            var_index i = solver->add_var(col->m_name);
+            c.add_variable_to_constraint(i, numeric_traits<T>::one());
+            solver->add_constraint(&c);
+        }
+
+        void create_upper_constraint_for_var(column* col, bound * b, lar_solver *solver) {
+            lar_constraint c(LE, b->m_upper);
+            var_index i = solver->add_var(col->m_name);
+            c.add_variable_to_constraint(i, numeric_traits<T>::one());
+            solver->add_constraint(&c);
+        }
+
+        void create_equality_contraint_for_var(column* col, bound * b, lar_solver *solver) {
+            lar_constraint c(EQ, b->m_fixed_value);
+            var_index i = solver->add_var(col->m_name);
+            c.add_variable_to_constraint(i, numeric_traits<T>::one());
+            solver->add_constraint(&c);
+        }
+
+        void fill_lar_solver_on_columns(lar_solver * solver) {
+            for (auto s : m_columns) {
+                mps_reader::column * col = s.second;
+                solver->add_var(col->m_name);
+                auto b = col->m_bound;
+                if (b == nullptr) return;
+
+                if (b->m_free) continue;
+
+                if (b->m_low_is_set) {
+                    create_low_constraint_for_var(col, b, solver);
+                }
+                if (b->m_upper_is_set) {
+                    create_upper_constraint_for_var(col, b, solver);
+                }
+                if (b->m_value_is_fixed) {
+                    create_equality_contraint_for_var(col, b, solver);
+                }
+            }
+        }
+        */
+
+        unsigned register_name(std::string s) {
+            auto it = m_name_to_var_index.find(s);
+            if (it!= m_name_to_var_index.end())
+                return it->second;
+
+            unsigned ret= m_name_to_var_index.size();
+            m_name_to_var_index[s] = ret;
+            return ret;
+        }
+        
+        void add_constraint_to_solver(lar_solver * solver, formula_constraint & fc) {
+            vector<std::pair<mpq, var_index>> ls;
+            for (auto & it : fc.m_coeffs) {
+                ls.push_back(std::make_pair(it.first, solver->add_var(register_name(it.second))));
+            }
+            solver->add_constraint(ls, fc.m_kind, fc.m_right_side);
+        }
+
+        void fill_lar_solver(lar_solver * solver) {
+            for (formula_constraint & fc : m_constraints)
+                add_constraint_to_solver(solver, fc);
+        }
+
+
+        lar_solver * create_lar_solver() {
+            lar_solver * ls = new lar_solver();
+            fill_lar_solver(ls);
+            return ls;
+        }
+    };
+}

src/test/test_file_reader.h

@@ -0,0 +1,73 @@
+/*
+Copyright (c) 2013 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Lev Nachmanson
+*/
+#pragma once
+
+// reads a text file
+#include <string>
+#include <vector>
+#include <unordered_map>
+#include <iostream>
+#include <fstream>
+#include "util/lp/lp_utils.h"
+#include "util/lp/lp_solver.h"
+
+namespace lean {
+
+template <typename T>
+struct test_result {
+    lp_status m_status;
+    T m_cost;
+    std::unordered_map<std::string, T> column_values;
+};
+
+template <typename T>
+class test_file_reader {
+    struct raw_blob {
+        std::vector<std::string> m_unparsed_strings;
+        std::vector<raw_blob> m_blobs;
+    };
+
+    struct test_file_blob {
+        std::string m_name;
+        std::string m_content;
+        std::unordered_map<std::string, std::string> m_table;
+        std::unordered_map<std::string, test_file_blob> m_blobs;
+
+        test_result<T> * get_test_result() {
+            test_result<T> * tr = new test_result<T>();
+            throw "not impl";
+            return tr;
+        }
+    };
+    std::ifstream m_file_stream;
+public:
+    // constructor
+    test_file_reader(std::string file_name) :  m_file_stream(file_name) {
+        if (!m_file_stream.is_open()) {
+            std::cout << "cannot open file " << "\'" << file_name << "\'" << std::endl;
+        }
+    }
+
+    raw_blob scan_to_row_blob() {
+    }
+
+    test_file_blob scan_row_blob_to_test_file_blob(raw_blob /* rblob */) {
+    }
+
+    test_result<T> * get_test_result() {
+        if (!m_file_stream.is_open()) {
+            return nullptr;
+        }
+
+        raw_blob rblob = scan_to_row_blob();
+
+        test_file_blob tblob = scan_row_blob_to_test_file_blob(rblob);
+
+        return tblob.get_test_result();
+    }
+};
+}

src/util/lp/binary_heap_priority_queue.h

@@ -0,0 +1,71 @@
+
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/vector.h"
+#include "util/debug.h"
+#include "util/lp/lp_utils.h"
+namespace lean {
+// the elements with the smallest priority are dequeued first
+template <typename T>
+class binary_heap_priority_queue {
+    vector<T> m_priorities;
+
+    // indexing for A starts from 1
+    vector<unsigned> m_heap; // keeps the elements of the queue
+    vector<int> m_heap_inverse; // o = m_heap[m_heap_inverse[o]]
+    unsigned m_heap_size = 0;
+
+    // is is the child place in heap
+    void swap_with_parent(unsigned i);
+    void put_at(unsigned i, unsigned h);
+    void decrease_priority(unsigned o, T newPriority);
+public:
+#ifdef LEAN_DEBUG
+    bool is_consistent() const;
+#endif
+public:
+    void remove(unsigned o);
+    unsigned size() const { return m_heap_size; }
+    binary_heap_priority_queue(): m_heap(1) {} // the empty constructror
+    // n is the initial queue capacity.
+    // The capacity will be enlarged two times automatically if needed
+    binary_heap_priority_queue(unsigned n);
+
+    void clear() {
+        for (unsigned i = 0; i < m_heap_size; i++) {
+            unsigned o = m_heap[i+1];
+            m_heap_inverse[o] = -1;
+        }
+        m_heap_size = 0;
+    }
+
+    void resize(unsigned n);
+    void put_to_heap(unsigned i, unsigned o);
+
+    void enqueue_new(unsigned o, const T& priority);
+
+    // This method can work with an element that is already in the queue.
+    // In this case the priority will be changed and the queue adjusted.
+    void enqueue(unsigned o, const T & priority);
+    void change_priority_for_existing(unsigned o, const T & priority);
+    T get_priority(unsigned o) const { return m_priorities[o]; }
+    bool is_empty() const { return m_heap_size == 0; }
+
+    /// return the first element of the queue and removes it from the queue
+    unsigned dequeue_and_get_priority(T & priority);
+    void fix_heap_under(unsigned i);
+    void put_the_last_at_the_top_and_fix_the_heap();
+    /// return the first element of the queue and removes it from the queue
+    unsigned dequeue();
+    unsigned peek() const {
+        lean_assert(m_heap_size > 0);
+        return m_heap[1];
+    }
+#ifdef LEAN_DEBUG
+    void print(std::ostream & out);
+#endif
+};
+}

src/util/lp/binary_heap_priority_queue.hpp

@@ -0,0 +1,193 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/vector.h"
+#include "util/lp/binary_heap_priority_queue.h"
+namespace lean {
+// is is the child place in heap
+template <typename T> void binary_heap_priority_queue<T>::swap_with_parent(unsigned i) {
+    unsigned parent = m_heap[i >> 1];
+    put_at(i >> 1, m_heap[i]);
+    put_at(i, parent);
+}
+
+template <typename T> void binary_heap_priority_queue<T>::put_at(unsigned i, unsigned h) {
+    m_heap[i] = h;
+    m_heap_inverse[h] = i;
+}
+
+template <typename T> void binary_heap_priority_queue<T>::decrease_priority(unsigned o, T newPriority) {
+    m_priorities[o] = newPriority;
+    int i = m_heap_inverse[o];
+    while (i > 1) {
+        if (m_priorities[m_heap[i]] < m_priorities[m_heap[i >> 1]])
+            swap_with_parent(i);
+        else
+            break;
+        i >>= 1;
+    }
+}
+
+#ifdef LEAN_DEBUG
+template <typename T> bool binary_heap_priority_queue<T>::is_consistent() const {
+    for (int i = 0; i < m_heap_inverse.size(); i++) {
+        int i_index = m_heap_inverse[i];
+        lean_assert(i_index <= static_cast<int>(m_heap_size));
+        lean_assert(i_index == -1 || m_heap[i_index] == i);
+    }
+    for (unsigned i = 1; i < m_heap_size; i++) {
+        unsigned ch = i << 1;
+        for (int k = 0; k < 2; k++) {
+            if (ch > m_heap_size) break;
+            if (!(m_priorities[m_heap[i]] <= m_priorities[m_heap[ch]])){
+                return false;
+            }
+            ch++;
+        }
+    }
+    return true;
+}
+#endif
+template <typename T> void binary_heap_priority_queue<T>::remove(unsigned o) {
+    T priority_of_o = m_priorities[o];
+    int o_in_heap = m_heap_inverse[o];
+    if (o_in_heap == -1)  {
+        return;  // nothing to do
+    }
+    lean_assert(static_cast<unsigned>(o_in_heap) <= m_heap_size);
+    if (static_cast<unsigned>(o_in_heap) < m_heap_size) {
+        put_at(o_in_heap, m_heap[m_heap_size--]);
+        if (m_priorities[m_heap[o_in_heap]] > priority_of_o) {
+            fix_heap_under(o_in_heap);
+        } else { // we need to propogate the m_heap[o_in_heap] up
+            unsigned i = o_in_heap;
+            while (i > 1) {
+                unsigned ip = i >> 1;
+                if (m_priorities[m_heap[i]] < m_priorities[m_heap[ip]])
+                    swap_with_parent(i);
+                else
+                    break;
+                i = ip;
+            }
+        }
+    } else {
+        lean_assert(static_cast<unsigned>(o_in_heap) == m_heap_size);
+        m_heap_size--;
+    }
+    m_heap_inverse[o] = -1;
+    // lean_assert(is_consistent());
+}
+// n is the initial queue capacity.
+// The capacity will be enlarged two times automatically if needed
+template <typename T> binary_heap_priority_queue<T>::binary_heap_priority_queue(unsigned n) :
+    m_priorities(n),
+    m_heap(n + 1), // because the indexing for A starts from 1
+    m_heap_inverse(n, -1)
+{ }
+
+
+template <typename T> void binary_heap_priority_queue<T>::resize(unsigned n) {
+    m_priorities.resize(n);
+    m_heap.resize(n + 1);
+    m_heap_inverse.resize(n, -1);
+}
+
+template <typename T> void binary_heap_priority_queue<T>::put_to_heap(unsigned i, unsigned o) {
+    m_heap[i] = o;
+    m_heap_inverse[o] = i;
+}
+
+template <typename T> void binary_heap_priority_queue<T>::enqueue_new(unsigned o, const T& priority) {
+    m_heap_size++;
+    int i = m_heap_size;
+    lean_assert(o < m_priorities.size());
+    m_priorities[o] = priority;
+    put_at(i, o);
+    while (i > 1 && m_priorities[m_heap[i >> 1]] > priority) {
+        swap_with_parent(i);
+        i >>= 1;
+    }
+}
+// This method can work with an element that is already in the queue.
+// In this case the priority will be changed and the queue adjusted.
+template <typename T> void binary_heap_priority_queue<T>::enqueue(unsigned o, const T & priority) {
+    if (o >= m_priorities.size()) {
+        resize(o << 1); // make the size twice larger
+    }
+    if (m_heap_inverse[o] == -1)
+        enqueue_new(o, priority);
+    else
+        change_priority_for_existing(o, priority);
+}
+
+template <typename T> void binary_heap_priority_queue<T>::change_priority_for_existing(unsigned o, const T & priority) {
+    if (m_priorities[o] > priority) {
+        decrease_priority(o, priority);
+    } else {
+        m_priorities[o] = priority;
+        fix_heap_under(m_heap_inverse[o]);
+    }
+}
+
+
+/// return the first element of the queue and removes it from the queue
+template <typename T> unsigned binary_heap_priority_queue<T>::dequeue_and_get_priority(T & priority) {
+    lean_assert(m_heap_size != 0);
+    int ret = m_heap[1];
+    priority = m_priorities[ret];
+    put_the_last_at_the_top_and_fix_the_heap();
+    return ret;
+}
+
+template <typename T> void binary_heap_priority_queue<T>::fix_heap_under(unsigned i) {
+    while (true) {
+        unsigned smallest = i;
+        unsigned l = i << 1;
+        if (l <= m_heap_size && m_priorities[m_heap[l]] < m_priorities[m_heap[i]])
+            smallest = l;
+        unsigned r = l + 1;
+        if (r <= m_heap_size && m_priorities[m_heap[r]] < m_priorities[m_heap[smallest]])
+            smallest = r;
+        if (smallest != i)
+            swap_with_parent(smallest);
+        else
+            break;
+        i = smallest;
+    }
+}
+
+template <typename T> void binary_heap_priority_queue<T>::put_the_last_at_the_top_and_fix_the_heap() {
+    if (m_heap_size > 1) {
+        put_at(1, m_heap[m_heap_size--]);
+        fix_heap_under(1);
+    } else {
+        m_heap_size--;
+    }
+}
+/// return the first element of the queue and removes it from the queue
+template <typename T> unsigned binary_heap_priority_queue<T>::dequeue() {
+    lean_assert(m_heap_size > 0);
+    int ret = m_heap[1];
+    put_the_last_at_the_top_and_fix_the_heap();
+    m_heap_inverse[ret] = -1;
+    return ret;
+}
+#ifdef LEAN_DEBUG
+template <typename T> void binary_heap_priority_queue<T>::print(std::ostream & out) {
+    vector<int> index;
+    vector<T> prs;
+    while (size()) {
+        T prior;
+        int j = dequeue_and_get_priority(prior);
+        index.push_back(j);
+        prs.push_back(prior);
+        out << "(" << j << ", " << prior << ")";
+    }
+    out << std::endl;
+    // restore the queue
+    for (int i = 0; i < index.size(); i++)
+        enqueue(index[i], prs[i]);
+}
+#endif
+}

src/util/lp/binary_heap_priority_queue_instances.cpp

@@ -0,0 +1,26 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/numeric_pair.h"
+#include "util/lp/binary_heap_priority_queue.hpp"
+namespace lean {
+template binary_heap_priority_queue<int>::binary_heap_priority_queue(unsigned int);
+template unsigned binary_heap_priority_queue<int>::dequeue();
+template void binary_heap_priority_queue<int>::enqueue(unsigned int, int const&);
+template void binary_heap_priority_queue<double>::enqueue(unsigned int, double const&);
+template void binary_heap_priority_queue<mpq>::enqueue(unsigned int, mpq const&);
+template void binary_heap_priority_queue<int>::remove(unsigned int);
+template unsigned binary_heap_priority_queue<numeric_pair<mpq> >::dequeue();
+template unsigned binary_heap_priority_queue<double>::dequeue();
+template unsigned binary_heap_priority_queue<mpq>::dequeue();
+template void binary_heap_priority_queue<numeric_pair<mpq> >::enqueue(unsigned int, numeric_pair<mpq> const&);
+template void binary_heap_priority_queue<numeric_pair<mpq> >::resize(unsigned int);
+template void lean::binary_heap_priority_queue<double>::resize(unsigned int);
+template binary_heap_priority_queue<unsigned int>::binary_heap_priority_queue(unsigned int);
+template void binary_heap_priority_queue<unsigned>::resize(unsigned int);
+template unsigned binary_heap_priority_queue<unsigned int>::dequeue();
+template void binary_heap_priority_queue<unsigned int>::enqueue(unsigned int, unsigned int const&);
+template void binary_heap_priority_queue<unsigned int>::remove(unsigned int);
+template void lean::binary_heap_priority_queue<mpq>::resize(unsigned int);
+}

src/util/lp/binary_heap_upair_queue.h

@@ -0,0 +1,50 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include <unordered_set>
+#include <unordered_map>
+#include <queue>
+#include "util/vector.h"
+#include <set>
+#include <utility>
+#include "util/lp/binary_heap_priority_queue.h"
+
+
+typedef std::pair<unsigned, unsigned> upair;
+
+namespace lean {
+template <typename  T>
+class binary_heap_upair_queue {
+    binary_heap_priority_queue<T> m_q;
+    std::unordered_map<upair, unsigned> m_pairs_to_index;
+    vector<upair> m_pairs; // inverse to index
+    vector<unsigned> m_available_spots;
+public:
+    binary_heap_upair_queue(unsigned size);
+
+    unsigned dequeue_available_spot();
+    bool is_empty() const { return m_q.is_empty(); }
+
+    unsigned size() const {return m_q.size(); }
+
+    bool contains(unsigned i, unsigned j) const { return m_pairs_to_index.find(std::make_pair(i, j)) != m_pairs_to_index.end();
+    }
+
+    void remove(unsigned i, unsigned j);
+    bool ij_index_is_new(unsigned ij_index) const;
+    void enqueue(unsigned i, unsigned j, const T & priority);
+    void dequeue(unsigned & i, unsigned &j);
+    T get_priority(unsigned i, unsigned j) const;
+#ifdef LEAN_DEBUG
+    bool pair_to_index_is_a_bijection() const;
+    bool available_spots_are_correct() const;
+    bool is_correct() const {
+        return m_q.is_consistent() && pair_to_index_is_a_bijection() && available_spots_are_correct();
+    }
+#endif
+    void resize(unsigned size) { m_q.resize(size); }
+};
+}

src/util/lp/binary_heap_upair_queue.hpp

@@ -0,0 +1,110 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#include <set>
+#include "util/lp/lp_utils.h"
+#include "util/lp/binary_heap_upair_queue.h"
+namespace lean {
+template <typename T> binary_heap_upair_queue<T>::binary_heap_upair_queue(unsigned size) : m_q(size), m_pairs(size) {
+    for (unsigned i = 0; i < size; i++)
+        m_available_spots.push_back(i);
+}
+
+template <typename T> unsigned
+binary_heap_upair_queue<T>::dequeue_available_spot() {
+    lean_assert(m_available_spots.empty() == false);
+    unsigned ret = m_available_spots.back();
+    m_available_spots.pop_back();
+    return ret;
+}
+
+template <typename T> void binary_heap_upair_queue<T>::remove(unsigned i, unsigned j) {
+    upair p(i, j);
+    auto it = m_pairs_to_index.find(p);
+    if (it == m_pairs_to_index.end())
+        return; // nothing to do
+    m_q.remove(it->second);
+    m_available_spots.push_back(it->second);
+    m_pairs_to_index.erase(it);
+}
+
+
+template <typename T> bool binary_heap_upair_queue<T>::ij_index_is_new(unsigned ij_index) const {
+    for (auto it : m_pairs_to_index) {
+        if (it.second == ij_index)
+            return false;
+    }
+    return true;
+}
+
+template <typename T> void binary_heap_upair_queue<T>::enqueue(unsigned i, unsigned j, const T & priority) {
+    upair p(i, j);
+    auto it = m_pairs_to_index.find(p);
+    unsigned ij_index;
+    if (it == m_pairs_to_index.end()) {
+        // it is a new pair, let us find a spot for it
+        if (m_available_spots.empty()) {
+            // we ran out of empty spots
+            unsigned size_was = static_cast<unsigned>(m_pairs.size());
+            unsigned new_size = size_was << 1;
+            for (unsigned i = size_was; i < new_size; i++)
+                m_available_spots.push_back(i);
+            m_pairs.resize(new_size);
+        }
+        ij_index = dequeue_available_spot();
+        // lean_assert(ij_index<m_pairs.size() && ij_index_is_new(ij_index));
+        m_pairs[ij_index] = p;
+        m_pairs_to_index[p] = ij_index;
+    } else {
+        ij_index = it->second;
+    }
+    m_q.enqueue(ij_index, priority);
+}
+
+template <typename T> void binary_heap_upair_queue<T>::dequeue(unsigned & i, unsigned &j) {
+    lean_assert(!m_q.is_empty());
+    unsigned ij_index = m_q.dequeue();
+    upair & p = m_pairs[ij_index];
+    i = p.first;
+    j = p.second;
+    m_available_spots.push_back(ij_index);
+    m_pairs_to_index.erase(p);
+}
+
+
+template <typename T> T binary_heap_upair_queue<T>::get_priority(unsigned i, unsigned j) const {
+    auto it =  m_pairs_to_index.find(std::make_pair(i, j));
+    if (it == m_pairs_to_index.end())
+        return T(0xFFFFFF); // big number
+    return m_q.get_priority(it->second);
+}
+
+#ifdef LEAN_DEBUG
+template <typename T> bool binary_heap_upair_queue<T>::pair_to_index_is_a_bijection() const {
+    std::set<int> tmp;
+    for (auto p : m_pairs_to_index) {
+        unsigned j = p.second;
+        unsigned size = tmp.size();
+        tmp.insert(j);
+        if (tmp.size() == size)
+            return false;
+    }
+    return true;
+}
+
+template <typename T> bool binary_heap_upair_queue<T>::available_spots_are_correct() const {
+    std::set<int> tmp;
+    for (auto p : m_available_spots){
+        tmp.insert(p);
+    }
+    if (tmp.size() != m_available_spots.size())
+        return false;
+    for (auto it : m_pairs_to_index)
+        if (tmp.find(it.second) != tmp.end())
+            return false;
+    return true;
+}
+#endif
+}

src/util/lp/binary_heap_upair_queue_instances.cpp

@@ -0,0 +1,17 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/binary_heap_upair_queue.hpp"
+namespace lean {
+template binary_heap_upair_queue<int>::binary_heap_upair_queue(unsigned int);
+template binary_heap_upair_queue<unsigned int>::binary_heap_upair_queue(unsigned int);
+template unsigned binary_heap_upair_queue<int>::dequeue_available_spot();
+template unsigned binary_heap_upair_queue<unsigned int>::dequeue_available_spot();
+template void binary_heap_upair_queue<int>::enqueue(unsigned int, unsigned int, int const&);
+template void binary_heap_upair_queue<int>::remove(unsigned int, unsigned int);
+template void binary_heap_upair_queue<unsigned int>::remove(unsigned int, unsigned int);
+template void binary_heap_upair_queue<int>::dequeue(unsigned int&, unsigned int&);
+template void binary_heap_upair_queue<unsigned int>::enqueue(unsigned int, unsigned int, unsigned int const&);
+template void binary_heap_upair_queue<unsigned int>::dequeue(unsigned int&, unsigned int&);
+}

src/util/lp/bound_analyzer_on_row.h

@@ -0,0 +1,333 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/vector.h"
+#include "util/lp/linear_combination_iterator.h"
+#include "implied_bound.h"
+#include "test_bound_analyzer.h"
+#include <functional>
+#include "util/lp/bound_propagator.h"
+// We have an equality : sum by j of row[j]*x[j] = rs
+// We try to pin a var by pushing the total by using the variable bounds
+// In a loop we drive the partial sum down, denoting the variables of this process by _u.
+// In the same loop trying to pin variables by pushing the partial sum up, denoting the variable related to it by _l
+namespace lean {
+
+class bound_analyzer_on_row {
+    
+    linear_combination_iterator<mpq> & m_it;
+    unsigned m_row_or_term_index;
+    int m_column_of_u = -1; // index of an unlimited from above monoid
+    // -1 means that such a value is not found, -2 means that at least two of such monoids were found
+    int m_column_of_l = -1; // index of an unlimited from below monoid
+    impq m_rs;
+    bound_propagator & m_bp;
+public :
+    // constructor
+    bound_analyzer_on_row(
+                          linear_combination_iterator<mpq> &it,
+                          const numeric_pair<mpq>& rs,
+                          unsigned row_or_term_index,
+                          bound_propagator & bp
+                          )
+        :
+        m_it(it),
+        m_row_or_term_index(row_or_term_index),
+        m_rs(rs),
+        m_bp(bp)
+    {}
+
+
+    unsigned j;
+    void analyze() {
+        
+        mpq a; unsigned j;
+        while (((m_column_of_l != -2) || (m_column_of_u != -2)) && m_it.next(a, j))
+            analyze_bound_on_var_on_coeff(j, a);
+
+        if (m_column_of_u >= 0)
+            limit_monoid_u_from_below();
+        else if (m_column_of_u == -1)
+            limit_all_monoids_from_below();
+
+        if (m_column_of_l >= 0)
+            limit_monoid_l_from_above();
+        else if (m_column_of_l == -1)
+            limit_all_monoids_from_above();
+    }
+
+    bool bound_is_available(unsigned j, bool low_bound) {
+        return (low_bound && low_bound_is_available(j)) ||
+            (!low_bound && upper_bound_is_available(j));
+    }
+
+    bool upper_bound_is_available(unsigned j) const {
+        switch (m_bp.get_column_type(j))
+        {
+        case column_type::fixed:
+        case column_type::boxed:
+        case column_type::upper_bound:
+            return true;
+        default:
+            return false;
+        }
+    }
+
+    bool low_bound_is_available(unsigned j) const {
+        switch (m_bp.get_column_type(j))
+        {
+        case column_type::fixed:
+        case column_type::boxed:
+        case column_type::low_bound:
+            return true;
+        default:
+            return false;
+        }
+    }
+
+    const impq & ub(unsigned j) const {
+        lean_assert(upper_bound_is_available(j));
+        return m_bp.get_upper_bound(j);
+    }
+    const impq & lb(unsigned j) const {
+        lean_assert(low_bound_is_available(j));
+        return m_bp.get_low_bound(j);
+    }
+
+
+    const mpq & monoid_max_no_mult(bool a_is_pos, unsigned j, bool & strict) const {
+        if (a_is_pos) {
+            strict = !is_zero(ub(j).y);
+            return ub(j).x;
+        }
+        strict = !is_zero(lb(j).y);
+        return lb(j).x;
+    }
+    mpq monoid_max(const mpq & a, unsigned j) const {
+        if (is_pos(a)) {
+            return a * ub(j).x;
+        }
+        return a * lb(j).x;
+    }
+	mpq monoid_max(const mpq & a, unsigned j, bool & strict) const {
+		if (is_pos(a)) {
+			strict = !is_zero(ub(j).y);
+			return a * ub(j).x;
+		}
+		strict = !is_zero(lb(j).y);
+		return a * lb(j).x;
+	}
+	const mpq & monoid_min_no_mult(bool a_is_pos, unsigned j, bool & strict) const {
+		if (!a_is_pos) {
+			strict = !is_zero(ub(j).y);
+			return ub(j).x;
+		}
+		strict = !is_zero(lb(j).y);
+		return lb(j).x;
+	}
+
+    mpq monoid_min(const mpq & a, unsigned j, bool& strict) const {
+        if (is_neg(a)) {
+            strict = !is_zero(ub(j).y);
+            return a * ub(j).x;
+        }
+        
+        strict = !is_zero(lb(j).y);
+        return a * lb(j).x;
+    }
+
+    mpq monoid_min(const mpq & a, unsigned j) const {
+        if (is_neg(a)) {
+            return a * ub(j).x;
+        }
+        
+        return a * lb(j).x;
+    }
+    
+
+    void limit_all_monoids_from_above() {
+        int strict = 0;
+        mpq total;
+        lean_assert(is_zero(total));
+        m_it.reset();
+        mpq a; unsigned j;
+        while (m_it.next(a, j)) {
+            bool str;
+            total -= monoid_min(a, j, str);
+            if (str)
+                strict++;
+        }
+
+        m_it.reset();
+        while (m_it.next(a, j)) {
+            bool str;
+			bool a_is_pos = is_pos(a);
+            mpq bound = total / a + monoid_min_no_mult(a_is_pos, j, str);
+            if (a_is_pos) {
+                limit_j(j, bound, true, false, strict - static_cast<int>(str) > 0);
+            }
+            else {
+                limit_j(j, bound, false, true, strict - static_cast<int>(str) > 0);
+            }
+        }
+    }
+
+    void limit_all_monoids_from_below() {
+        int strict = 0;
+        mpq total;
+        lean_assert(is_zero(total));
+        m_it.reset();
+        mpq a; unsigned j;
+        while (m_it.next(a, j)) {
+            bool str;
+            total -= monoid_max(a, j, str);
+            if (str)
+                strict++;
+        }
+        m_it.reset();
+        while (m_it.next(a, j)) {
+            bool str;
+			bool a_is_pos = is_pos(a);
+			mpq bound = total / a + monoid_max_no_mult(a_is_pos, j, str);
+            bool astrict = strict - static_cast<int>(str) > 0; 
+            if (a_is_pos) {
+                limit_j(j, bound, true, true, astrict);
+            }
+            else {
+                limit_j(j, bound, false, false, astrict);
+            }
+        }
+    }
+
+    
+    void limit_monoid_u_from_below() {
+        // we are going to limit from below the monoid m_column_of_u,
+        // every other monoid is impossible to limit from below
+        mpq u_coeff, a;
+        unsigned j;
+        mpq bound = -m_rs.x;
+        m_it.reset();
+        bool strict = false;
+        while (m_it.next(a, j)) {
+            if (j == static_cast<unsigned>(m_column_of_u)) {
+                u_coeff = a;
+                continue;
+            }
+            bool str;
+            bound -= monoid_max(a, j, str);
+            if (str)
+                strict = true;
+        }
+
+        bound /= u_coeff;
+        
+        if (numeric_traits<impq>::is_pos(u_coeff)) {
+            limit_j(m_column_of_u, bound, true, true, strict);
+        } else {
+            limit_j(m_column_of_u, bound, false, false, strict);
+        }
+    }
+
+
+    void limit_monoid_l_from_above() {
+        // we are going to limit from above the monoid m_column_of_l,
+        // every other monoid is impossible to limit from above
+        mpq l_coeff, a;
+        unsigned j;
+        mpq bound = -m_rs.x;
+        bool strict = false;
+        m_it.reset();
+        while (m_it.next(a, j)) {
+            if (j == static_cast<unsigned>(m_column_of_l)) {
+                l_coeff = a;
+                continue;
+            }
+
+            bool str;
+            bound -= monoid_min(a, j, str);
+            if (str)
+                strict = true;
+        }
+
+        bound /= l_coeff;
+        if (is_pos(l_coeff)) {
+            limit_j(m_column_of_l, bound, true, false, strict);
+        } else {
+            limit_j(m_column_of_l, bound, false, true, strict);
+        }
+    }
+    
+    // // it is the coefficent before the bounded column
+    // void provide_evidence(bool coeff_is_pos) {
+    //     /*
+    //     auto & be = m_ibounds.back();
+    //     bool low_bound = be.m_low_bound;
+    //     if (!coeff_is_pos)
+    //         low_bound = !low_bound;
+    //     auto it = m_it.clone();
+    //     mpq a; unsigned j;
+    //     while (it->next(a, j)) {
+    //         if (be.m_j == j) continue;
+    //         lean_assert(bound_is_available(j, is_neg(a) ? low_bound : !low_bound));
+    //         be.m_vector_of_bound_signatures.emplace_back(a, j, numeric_traits<impq>::
+    //                                                      is_neg(a)? low_bound: !low_bound);
+    //     }
+    //     delete it;
+    //     */
+    // }
+
+    void limit_j(unsigned j, const mpq& u, bool coeff_before_j_is_pos, bool is_low_bound, bool strict){
+        m_bp.try_add_bound(u, j, is_low_bound, coeff_before_j_is_pos, m_row_or_term_index, strict);
+    }
+
+    
+    void advance_u(unsigned j) {
+        if (m_column_of_u == -1)
+            m_column_of_u = j;
+        else
+            m_column_of_u = -2;
+    }
+    
+    void advance_l(unsigned j) {
+        if (m_column_of_l == -1)
+            m_column_of_l = j;
+        else
+            m_column_of_l = -2;
+    }
+    
+    void analyze_bound_on_var_on_coeff(int j, const mpq &a) {
+        switch (m_bp.get_column_type(j)) {
+        case column_type::low_bound:
+            if (numeric_traits<mpq>::is_pos(a))
+                advance_u(j);
+            else 
+                advance_l(j);
+            break;
+        case column_type::upper_bound:
+            if(numeric_traits<mpq>::is_neg(a))
+                advance_u(j);
+            else
+                advance_l(j);
+            break;
+        case column_type::free_column:
+            advance_u(j);
+            advance_l(j);
+            break;
+        default:
+            break;
+        }
+    }
+
+    static void analyze_row(linear_combination_iterator<mpq> &it,
+                            const numeric_pair<mpq>& rs,
+                            unsigned row_or_term_index,
+                            bound_propagator & bp
+                            ) {
+        bound_analyzer_on_row a(it, rs, row_or_term_index, bp);
+        a.analyze();
+    }
+
+};
+}

src/util/lp/bound_propagator.cpp

@@ -0,0 +1,47 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/lar_solver.h"
+namespace lean {
+bound_propagator::bound_propagator(lar_solver & ls):
+    m_lar_solver(ls) {}
+column_type bound_propagator::get_column_type(unsigned j) const {
+    return m_lar_solver.m_mpq_lar_core_solver.m_column_types()[j];
+}
+const impq & bound_propagator::get_low_bound(unsigned j) const {
+    return m_lar_solver.m_mpq_lar_core_solver.m_r_low_bounds()[j];
+}
+const impq & bound_propagator::get_upper_bound(unsigned j) const {
+    return m_lar_solver.m_mpq_lar_core_solver.m_r_upper_bounds()[j];
+}
+void bound_propagator::try_add_bound(const mpq & v, unsigned j, bool is_low, bool coeff_before_j_is_pos, unsigned row_or_term_index, bool strict) {
+    j = m_lar_solver.adjust_column_index_to_term_index(j);
+    lconstraint_kind kind = is_low? GE : LE;
+    if (strict)
+        kind = static_cast<lconstraint_kind>(kind / 2);
+    
+    if (!bound_is_interesting(j, kind, v))
+        return;
+     unsigned k; // index to ibounds
+     if (is_low) {
+         if (try_get_val(m_improved_low_bounds, j, k)) {
+             auto & found_bound = m_ibounds[k];
+             if (v > found_bound.m_bound || (v == found_bound.m_bound && found_bound.m_strict == false && strict))
+                 found_bound = implied_bound(v, j, is_low, coeff_before_j_is_pos, row_or_term_index, strict);
+         } else {
+             m_improved_low_bounds[j] = m_ibounds.size();
+             m_ibounds.push_back(implied_bound(v, j, is_low, coeff_before_j_is_pos, row_or_term_index, strict));
+         }
+     } else { // the upper bound case
+         if (try_get_val(m_improved_upper_bounds, j, k)) {
+             auto & found_bound = m_ibounds[k];
+             if (v < found_bound.m_bound || (v == found_bound.m_bound && found_bound.m_strict == false && strict))
+                 found_bound = implied_bound(v, j, is_low, coeff_before_j_is_pos, row_or_term_index, strict);
+         } else {
+             m_improved_upper_bounds[j] = m_ibounds.size();
+             m_ibounds.push_back(implied_bound(v, j, is_low, coeff_before_j_is_pos, row_or_term_index, strict));
+        }
+     }
+}
+}

src/util/lp/bound_propagator.h

@@ -0,0 +1,27 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/lp_settings.h"
+namespace lean {
+class lar_solver;
+class bound_propagator {
+    std::unordered_map<unsigned, unsigned> m_improved_low_bounds; // these maps map a column index to the corresponding index in ibounds
+    std::unordered_map<unsigned, unsigned> m_improved_upper_bounds;
+    lar_solver & m_lar_solver;
+public:
+    vector<implied_bound> m_ibounds;
+public:
+    bound_propagator(lar_solver & ls);
+    column_type get_column_type(unsigned) const;
+    const impq & get_low_bound(unsigned) const;
+    const impq & get_upper_bound(unsigned) const;
+    void try_add_bound(const mpq & v, unsigned j, bool is_low, bool coeff_before_j_is_pos, unsigned row_or_term_index, bool strict);
+    virtual bool bound_is_interesting(unsigned vi,
+                                      lean::lconstraint_kind kind,
+                                      const rational & bval) {return true;}
+    unsigned number_of_found_bounds() const { return m_ibounds.size(); }
+    virtual void consume(mpq const& v, unsigned j) { std::cout << "doh\n"; }
+};
+}

src/util/lp/breakpoint.h

@@ -0,0 +1,20 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+
+namespace lean {
+enum breakpoint_type {
+    low_break, upper_break, fixed_break
+};
+template <typename X>
+struct breakpoint {
+    unsigned m_j; // the basic column
+    breakpoint_type m_type;
+    X m_delta;
+    breakpoint(){}
+    breakpoint(unsigned j, X delta, breakpoint_type type):m_j(j), m_type(type), m_delta(delta) {}
+};
+}

src/util/lp/column_info.h

@@ -0,0 +1,235 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include <unordered_map>
+#include <string>
+#include <algorithm>
+#include "util/lp/lp_settings.h"
+namespace lean {
+inline bool is_valid(unsigned j) { return static_cast<int>(j) >= 0;}
+
+template <typename T>
+class column_info {
+    std::string m_name;
+    bool m_low_bound_is_set = false;
+    bool m_low_bound_is_strict = false;
+    bool m_upper_bound_is_set = false;
+    bool m_upper_bound_is_strict = false;
+    T m_low_bound;
+    T m_upper_bound;
+    T m_cost = numeric_traits<T>::zero();
+    T m_fixed_value;
+    bool m_is_fixed = false;
+    unsigned m_column_index = static_cast<unsigned>(-1);
+public:
+    bool operator==(const column_info & c) const {
+        return     m_name == c.m_name &&
+            m_low_bound_is_set == c.m_low_bound_is_set &&
+            m_low_bound_is_strict == c.m_low_bound_is_strict &&
+            m_upper_bound_is_set == c.m_upper_bound_is_set&&
+            m_upper_bound_is_strict == c.m_upper_bound_is_strict&&
+            (!m_low_bound_is_set || m_low_bound == c.m_low_bound) &&
+            (!m_upper_bound_is_set || m_upper_bound == c.m_upper_bound) &&
+            m_cost == c.m_cost&&
+            m_is_fixed == c.m_is_fixed &&
+            (!m_is_fixed || m_fixed_value == c.m_fixed_value) &&
+            m_column_index == c.m_column_index;
+    }
+    bool operator!=(const column_info & c) const { return !((*this) == c); }
+    void set_column_index(unsigned j) {
+        m_column_index = j;
+    }
+    // the default constructor
+    column_info() {}
+
+    column_info(unsigned column_index) : m_column_index(column_index) {
+    }
+
+    column_info(const column_info & ci) {
+        m_name = ci.m_name;
+        m_low_bound_is_set = ci.m_low_bound_is_set;
+        m_low_bound_is_strict = ci.m_low_bound_is_strict;
+        m_upper_bound_is_set = ci.m_upper_bound_is_set;
+        m_upper_bound_is_strict = ci.m_upper_bound_is_strict;
+        m_low_bound = ci.m_low_bound;
+        m_upper_bound = ci.m_upper_bound;
+        m_cost = ci.m_cost;
+        m_fixed_value = ci.m_fixed_value;
+        m_is_fixed = ci.m_is_fixed;
+        m_column_index = ci.m_column_index;
+    }
+
+    unsigned get_column_index() const {
+        return m_column_index;
+    }
+
+    column_type get_column_type() const {
+        return m_is_fixed? column_type::fixed : (m_low_bound_is_set? (m_upper_bound_is_set? column_type::boxed : column_type::low_bound) : (m_upper_bound_is_set? column_type::upper_bound: column_type::free_column));
+    }
+
+    column_type get_column_type_no_flipping() const {
+        if (m_is_fixed) {
+            return column_type::fixed;
+        }
+
+        if (m_low_bound_is_set) {
+            return m_upper_bound_is_set? column_type::boxed: column_type::low_bound;
+        }
+        // we are flipping the bounds!
+        return m_upper_bound_is_set? column_type::upper_bound
+            : column_type::free_column;
+    }
+
+    T get_low_bound() const {
+        lean_assert(m_low_bound_is_set);
+        return m_low_bound;
+    }
+    T get_upper_bound() const {
+        lean_assert(m_upper_bound_is_set);
+        return m_upper_bound;
+    }
+
+    bool low_bound_is_set() const {
+        return m_low_bound_is_set;
+    }
+
+    bool upper_bound_is_set() const {
+        return m_upper_bound_is_set;
+    }
+
+    T get_shift() {
+        if (is_fixed()) {
+            return m_fixed_value;
+        }
+        if (is_flipped()){
+            return m_upper_bound;
+        }
+        return m_low_bound_is_set? m_low_bound : numeric_traits<T>::zero();
+    }
+
+    bool is_flipped() {
+        return m_upper_bound_is_set && !m_low_bound_is_set;
+    }
+
+    bool adjusted_low_bound_is_set() {
+        return !is_flipped()? low_bound_is_set(): upper_bound_is_set();
+    }
+
+    bool adjusted_upper_bound_is_set() {
+        return !is_flipped()? upper_bound_is_set(): low_bound_is_set();
+    }
+
+    T  get_adjusted_upper_bound() {
+        return get_upper_bound() - get_low_bound();
+    }
+
+    bool is_fixed() const {
+        return m_is_fixed;
+    }
+
+    bool is_free() {
+        return !m_low_bound_is_set && !m_upper_bound_is_set;
+    }
+
+    void set_fixed_value(T v) {
+        m_is_fixed = true;
+        m_fixed_value = v;
+    }
+
+    T get_fixed_value() const {
+        lean_assert(m_is_fixed);
+        return m_fixed_value;
+    }
+
+    T get_cost() const {
+        return m_cost;
+    }
+
+    void set_cost(T const & cost) {
+        m_cost = cost;
+    }
+
+    void set_name(std::string const & s) {
+        m_name = s;
+    }
+
+    std::string get_name() const {
+        return m_name;
+    }
+
+    void set_low_bound(T const & l) {
+        m_low_bound = l;
+        m_low_bound_is_set = true;
+    }
+
+    void set_upper_bound(T const & l) {
+        m_upper_bound = l;
+        m_upper_bound_is_set = true;
+    }
+
+    void unset_low_bound() {
+        m_low_bound_is_set = false;
+    }
+
+    void unset_upper_bound() {
+        m_upper_bound_is_set = false;
+    }
+
+    void unset_fixed() {
+        m_is_fixed = false;
+    }
+
+    bool low_bound_holds(T v) {
+        return !low_bound_is_set() || v >= m_low_bound -T(0.0000001);
+    }
+
+    bool upper_bound_holds(T v) {
+        return !upper_bound_is_set() || v <= m_upper_bound + T(0.000001);
+    }
+
+    bool bounds_hold(T v) {
+        return low_bound_holds(v) && upper_bound_holds(v);
+    }
+
+    bool adjusted_bounds_hold(T v) {
+        return adjusted_low_bound_holds(v) && adjusted_upper_bound_holds(v);
+    }
+
+    bool adjusted_low_bound_holds(T v) {
+        return !adjusted_low_bound_is_set() || v >= -T(0.0000001);
+    }
+
+    bool adjusted_upper_bound_holds(T v) {
+        return !adjusted_upper_bound_is_set() || v <= get_adjusted_upper_bound() + T(0.000001);
+    }
+    bool is_infeasible() {
+        if ((!upper_bound_is_set()) || (!low_bound_is_set()))
+            return false;
+        // ok, both bounds are set
+        bool at_least_one_is_strict = upper_bound_is_strict() || low_bound_is_strict();
+        if (!at_least_one_is_strict)
+            return get_upper_bound() < get_low_bound();
+        // at least on bound is strict
+        return get_upper_bound() <= get_low_bound(); // the equality is impossible
+    }
+    bool low_bound_is_strict() const {
+        return m_low_bound_is_strict;
+    }
+
+    void set_low_bound_strict(bool val) {
+        m_low_bound_is_strict = val;
+    }
+
+    bool upper_bound_is_strict() const {
+        return m_upper_bound_is_strict;
+    }
+
+    void set_upper_bound_strict(bool val) {
+        m_upper_bound_is_strict = val;
+    }
+};
+}

src/util/lp/column_namer.h

@@ -0,0 +1,82 @@
+#pragma once
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <string>
+#include "util/lp/linear_combination_iterator.h"
+namespace lean {
+class column_namer {
+public:
+    virtual std::string get_column_name(unsigned j) const = 0;
+    template <typename T>
+    void print_linear_iterator(linear_combination_iterator<T>* it, std::ostream & out) const {
+        vector<std::pair<T, unsigned>> coeff;
+        T a;
+        unsigned i;
+        while (it->next(a, i)) {
+            coeff.emplace_back(a, i);
+        }
+        print_linear_combination_of_column_indices(coeff, out);
+    }
+    template <typename T>
+    void print_linear_iterator_indices_only(linear_combination_iterator<T>* it, std::ostream & out) const {
+        vector<std::pair<T, unsigned>> coeff;
+        T a;
+        unsigned i;
+        while (it->next(a, i)) {
+            coeff.emplace_back(a, i);
+        }
+        print_linear_combination_of_column_indices_only(coeff, out);
+    }
+    
+    template <typename T>
+    void print_linear_combination_of_column_indices_only(const vector<std::pair<T, unsigned>> & coeffs, std::ostream & out) const {
+        bool first = true;
+        for (const auto & it : coeffs) {
+            auto val = it.first;
+            if (first) {
+                first = false;
+            } else {
+                if (numeric_traits<T>::is_pos(val)) {
+                    out << " + ";
+                } else {
+                    out << " - ";
+                    val = -val;
+                }
+            }
+            if (val == -numeric_traits<T>::one())
+                out << " - ";
+            else if (val != numeric_traits<T>::one())
+                out << T_to_string(val);
+        
+            out << "_" << it.second;
+        }
+    }
+    
+    template <typename T>
+    void print_linear_combination_of_column_indices(const vector<std::pair<T, unsigned>> & coeffs, std::ostream & out) const {
+        bool first = true;
+        for (const auto & it : coeffs) {
+            auto val = it.first;
+            if (first) {
+                first = false;
+            } else {
+                if (numeric_traits<T>::is_pos(val)) {
+                    out << " + ";
+                } else {
+                    out << " - ";
+                    val = -val;
+                }
+            }
+            if (val == -numeric_traits<T>::one())
+                out << " - ";
+            else if (val != numeric_traits<T>::one())
+                out << val;
+        
+            out << get_column_name(it.second);
+        }
+    }
+
+};
+}

src/util/lp/core_solver_pretty_printer.h

@@ -0,0 +1,118 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include <limits>
+#include <string>
+#include <algorithm>
+#include "util/vector.h"
+#include <ostream>
+#include "util/lp/lp_settings.h"
+#include "util/lp/indexed_vector.h"
+namespace lean {
+template <typename T, typename X> class lp_core_solver_base; // forward definition
+
+template <typename T, typename X>
+class core_solver_pretty_printer {
+    std::ostream & m_out;
+    template<typename A> using vector = vector<A>;
+    typedef std::string string;
+    lp_core_solver_base<T, X> & m_core_solver;
+    vector<unsigned> m_column_widths;
+    vector<vector<string>> m_A;
+    vector<vector<string>> m_signs;
+    vector<string> m_costs;
+    vector<string> m_cost_signs;
+    vector<string> m_lows; // low bounds
+    vector<string> m_upps; // upper bounds
+    vector<string> m_lows_signs;
+    vector<string> m_upps_signs;
+    unsigned m_rs_width;
+    vector<X> m_rs;
+    unsigned m_title_width;
+    std::string m_cost_title;
+    std::string m_basis_heading_title;
+    std::string m_x_title;
+    std::string m_low_bounds_title = "low";
+    std::string m_upp_bounds_title = "upp";
+    std::string m_exact_norm_title = "exact cn";
+    std::string m_approx_norm_title = "approx cn";
+
+
+    unsigned ncols() { return m_core_solver.m_A.column_count(); }
+    unsigned nrows() { return m_core_solver.m_A.row_count(); }
+    unsigned m_artificial_start = std::numeric_limits<unsigned>::max();
+    indexed_vector<T> m_w_buff;
+    indexed_vector<T> m_ed_buff;
+    vector<T> m_exact_column_norms;
+
+public:
+    core_solver_pretty_printer(lp_core_solver_base<T, X > & core_solver, std::ostream & out);
+
+    void init_costs();
+
+    ~core_solver_pretty_printer();
+    void init_rs_width();
+
+    T current_column_norm();
+
+    void init_m_A_and_signs();
+
+    void init_column_widths();
+
+    void adjust_width_with_low_bound(unsigned column, unsigned & w);
+    void adjust_width_with_upper_bound(unsigned column, unsigned & w);
+
+    void adjust_width_with_bounds(unsigned column, unsigned & w);
+
+    void adjust_width_with_basis_heading(unsigned column, unsigned & w) {
+        w = std::max(w, (unsigned)T_to_string(m_core_solver.m_basis_heading[column]).size());
+    }
+
+    unsigned get_column_width(unsigned column);
+
+    unsigned regular_cell_width(unsigned row, unsigned column, std::string name) {
+        return regular_cell_string(row, column, name).size();
+    }
+
+    std::string regular_cell_string(unsigned row, unsigned column, std::string name);
+
+
+    void set_coeff(vector<string>& row, vector<string> & row_signs, unsigned col, const T & t, string name);
+
+    void print_x();
+
+    std::string get_low_bound_string(unsigned j);
+
+    std::string get_upp_bound_string(unsigned j);
+
+
+    void print_lows();
+
+    void print_upps();
+
+    string get_exact_column_norm_string(unsigned col) {
+        return T_to_string(m_exact_column_norms[col]);
+    }
+
+    void print_exact_norms();
+
+    void print_approx_norms();
+
+    void print();
+
+    void print_basis_heading();
+
+    void print_bottom_line() {
+        m_out << "----------------------" << std::endl;
+    }
+
+    void print_cost();
+
+    void print_given_rows(vector<string> & row, vector<string> & signs, X rst);
+
+    void print_row(unsigned i);
+
+};
+}

src/util/lp/core_solver_pretty_printer.hpp

@@ -0,0 +1,377 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <limits>
+#include <string>
+#include <algorithm>
+#include "util/lp/lp_utils.h"
+#include "util/lp/lp_core_solver_base.h"
+#include "util/lp/core_solver_pretty_printer.h"
+#include "util/lp/numeric_pair.h"
+namespace lean {
+
+
+template <typename T, typename X>
+core_solver_pretty_printer<T, X>::core_solver_pretty_printer(lp_core_solver_base<T, X > & core_solver, std::ostream & out):
+    m_out(out),
+    m_core_solver(core_solver),
+    m_A(core_solver.m_A.row_count(), vector<string>(core_solver.m_A.column_count(), "")),
+    m_signs(core_solver.m_A.row_count(), vector<string>(core_solver.m_A.column_count(), " ")),
+    m_costs(ncols(), ""),
+    m_cost_signs(ncols(), " "),
+    m_rs(ncols(), zero_of_type<X>()),
+    m_w_buff(core_solver.m_w),
+    m_ed_buff(core_solver.m_ed) {
+    m_column_widths.resize(core_solver.m_A.column_count(), 0),
+    init_m_A_and_signs();
+    init_costs();
+    init_column_widths();
+    init_rs_width();
+    m_cost_title = "costs";
+    m_basis_heading_title = "heading";
+    m_x_title = "x*";
+    m_title_width = static_cast<unsigned>(std::max(std::max(m_cost_title.size(), std::max(m_basis_heading_title.size(), m_x_title.size())), m_approx_norm_title.size()));
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::init_costs() {
+    if (!m_core_solver.use_tableau()) {
+        vector<T> local_y(m_core_solver.m_m());
+        m_core_solver.solve_yB(local_y);
+        for (unsigned i = 0; i < ncols(); i++) {
+            if (m_core_solver.m_basis_heading[i] < 0) {
+                T t = m_core_solver.m_costs[i] - m_core_solver.m_A.dot_product_with_column(local_y, i);
+                set_coeff(m_costs, m_cost_signs, i, t, m_core_solver.column_name(i));
+            }
+        }
+    } else {
+        for (unsigned i = 0; i < ncols(); i++) {
+            if (m_core_solver.m_basis_heading[i] < 0) {
+                set_coeff(m_costs, m_cost_signs, i, m_core_solver.m_d[i], m_core_solver.column_name(i));
+            }
+        }
+    }
+}
+
+template <typename T, typename X> core_solver_pretty_printer<T, X>::~core_solver_pretty_printer() {
+    m_core_solver.m_w = m_w_buff;
+    m_core_solver.m_ed = m_ed_buff;
+}
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::init_rs_width() {
+    m_rs_width = static_cast<unsigned>(T_to_string(m_core_solver.get_cost()).size());
+    for (unsigned i = 0; i < nrows(); i++) {
+        unsigned wt = static_cast<unsigned>(T_to_string(m_rs[i]).size());
+        if (wt > m_rs_width) {
+            m_rs_width = wt;
+        }
+    }
+}
+
+template <typename T, typename X> T core_solver_pretty_printer<T, X>::current_column_norm() {
+    T ret = zero_of_type<T>();
+    for (auto i : m_core_solver.m_ed.m_index)
+        ret += m_core_solver.m_ed[i] * m_core_solver.m_ed[i];
+    return ret;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::init_m_A_and_signs() { 
+    if (numeric_traits<T>::precise() && m_core_solver.m_settings.use_tableau()) {
+        for (unsigned column = 0; column < ncols(); column++) {
+            vector<T> t(nrows(), zero_of_type<T>());
+            for (const auto & c : m_core_solver.m_A.m_columns[column]){
+                t[c.m_i] = m_core_solver.m_A.get_val(c);
+            }
+                
+            string name = m_core_solver.column_name(column);
+            for (unsigned row = 0; row < nrows(); row ++) {
+                set_coeff(
+                          m_A[row],
+                          m_signs[row],
+                          column,
+                          t[row],
+                          name);
+                m_rs[row] += t[row] * m_core_solver.m_x[column];
+            }
+        }
+    } else {
+        for (unsigned column = 0; column < ncols(); column++) {
+            m_core_solver.solve_Bd(column); // puts the result into m_core_solver.m_ed
+            string name = m_core_solver.column_name(column);
+            for (unsigned row = 0; row < nrows(); row ++) {
+                set_coeff(
+                          m_A[row],
+                          m_signs[row],
+                          column,
+                          m_core_solver.m_ed[row],
+                          name);
+                m_rs[row] += m_core_solver.m_ed[row] * m_core_solver.m_x[column];
+            }
+            if (!m_core_solver.use_tableau())
+                m_exact_column_norms.push_back(current_column_norm() + T(1)); // a conversion missing 1 -> T
+        }
+    }
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::init_column_widths() {
+    for (unsigned i = 0; i < ncols(); i++) {
+        m_column_widths[i] = get_column_width(i);
+    }
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::adjust_width_with_low_bound(unsigned column, unsigned & w) {
+    if (!m_core_solver.low_bounds_are_set()) return;
+    w = std::max(w, (unsigned)T_to_string(m_core_solver.low_bound_value(column)).size());
+}
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::adjust_width_with_upper_bound(unsigned column, unsigned & w) {
+    w = std::max(w, (unsigned)T_to_string(m_core_solver.upper_bound_value(column)).size());
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::adjust_width_with_bounds(unsigned column, unsigned & w) {
+    switch (m_core_solver.get_column_type(column)) {
+    case column_type::fixed:
+    case column_type::boxed:
+        adjust_width_with_low_bound(column, w);
+        adjust_width_with_upper_bound(column, w);
+        break;
+    case column_type::low_bound:
+        adjust_width_with_low_bound(column, w);
+        break;
+    case column_type::upper_bound:
+        adjust_width_with_upper_bound(column, w);
+        break;
+    case column_type::free_column:
+        break;
+    default:
+        lean_assert(false);
+        break;
+    }
+}
+
+
+template <typename T, typename X> unsigned core_solver_pretty_printer<T, X>:: get_column_width(unsigned column) {
+    unsigned w = static_cast<unsigned>(std::max((size_t)m_costs[column].size(), T_to_string(m_core_solver.m_x[column]).size()));
+    adjust_width_with_bounds(column, w);
+    adjust_width_with_basis_heading(column, w);
+    for (unsigned i = 0; i < nrows(); i++) {
+        unsigned cellw = static_cast<unsigned>(m_A[i][column].size());
+        if (cellw > w) {
+            w = cellw;
+        }
+    }
+    if (!m_core_solver.use_tableau()) {
+        w = std::max(w, (unsigned)T_to_string(m_exact_column_norms[column]).size());
+        if (m_core_solver.m_column_norms.size() > 0)
+            w = std::max(w, (unsigned)T_to_string(m_core_solver.m_column_norms[column]).size());
+    }
+    return w;
+}
+
+template <typename T, typename X> std::string core_solver_pretty_printer<T, X>::regular_cell_string(unsigned row, unsigned /* column */, std::string name) {
+    T t = fabs(m_core_solver.m_ed[row]);
+    if ( t == 1) return name;
+    return T_to_string(t) + name;
+}
+
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::set_coeff(vector<string>& row, vector<string> & row_signs, unsigned col, const T & t, string name) {
+    if (numeric_traits<T>::is_zero(t)) {
+        return;
+    }
+    if (col > 0) {
+        if (t > 0) {
+            row_signs[col] = "+";
+            row[col] = t != 1? T_to_string(t) + name : name;
+        } else {
+            row_signs[col] = "-";
+            row[col] = t != -1? T_to_string(-t) + name: name;
+        }
+    } else { // col == 0
+        if (t == -1) {
+            row[col] = "-" + name;
+        } else if (t == 1) {
+            row[col] = name;
+        } else {
+            row[col] = T_to_string(t) + name;
+        }
+    }
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_x() {
+    if (ncols() == 0) {
+        return;
+    }
+
+    int blanks = m_title_width + 1 - static_cast<int>(m_x_title.size());
+    m_out << m_x_title;
+    print_blanks(blanks, m_out);
+
+    auto bh = m_core_solver.m_x;
+    for (unsigned i = 0; i < ncols(); i++) {
+        string s = T_to_string(bh[i]);
+        int blanks = m_column_widths[i] - static_cast<int>(s.size());
+        print_blanks(blanks, m_out);
+        m_out << s << "   "; // the column interval
+    }
+    m_out << std::endl;
+}
+
+template <typename T, typename X> std::string core_solver_pretty_printer<T, X>::get_low_bound_string(unsigned j) {
+    switch (m_core_solver.get_column_type(j)){
+    case column_type::boxed:
+    case column_type::low_bound:
+    case column_type::fixed:
+        if (m_core_solver.low_bounds_are_set())
+            return T_to_string(m_core_solver.low_bound_value(j));
+        else
+            return std::string("0");
+        break;
+    default:
+        return std::string();
+    }
+}
+
+template <typename T, typename X> std::string core_solver_pretty_printer<T, X>::get_upp_bound_string(unsigned j) {
+    switch (m_core_solver.get_column_type(j)){
+    case column_type::boxed:
+    case column_type::upper_bound:
+    case column_type::fixed:
+        return T_to_string(m_core_solver.upper_bound_value(j));
+        break;
+    default:
+        return std::string();
+    }
+}
+
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_lows() {
+    if (ncols() == 0) {
+        return;
+    }
+    int blanks = m_title_width + 1 - static_cast<unsigned>(m_low_bounds_title.size());
+    m_out << m_low_bounds_title;
+    print_blanks(blanks, m_out);
+
+    for (unsigned i = 0; i < ncols(); i++) {
+        string s = get_low_bound_string(i);
+        int blanks = m_column_widths[i] - static_cast<unsigned>(s.size());
+        print_blanks(blanks, m_out);
+        m_out << s << "   "; // the column interval
+    }
+    m_out << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_upps() {
+    if (ncols() == 0) {
+        return;
+    }
+    int blanks = m_title_width + 1 - static_cast<unsigned>(m_upp_bounds_title.size());
+    m_out << m_upp_bounds_title;
+    print_blanks(blanks, m_out);
+
+    for (unsigned i = 0; i < ncols(); i++) {
+        string s = get_upp_bound_string(i);
+        int blanks = m_column_widths[i] - static_cast<unsigned>(s.size());
+        print_blanks(blanks, m_out);
+        m_out << s << "   "; // the column interval
+    }
+    m_out << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_exact_norms() {
+    if (m_core_solver.use_tableau()) return;
+    int blanks = m_title_width + 1 - static_cast<int>(m_exact_norm_title.size());
+    m_out << m_exact_norm_title;
+    print_blanks(blanks, m_out);
+    for (unsigned i = 0; i < ncols(); i++) {
+        string s = get_exact_column_norm_string(i);
+        int blanks = m_column_widths[i] - static_cast<int>(s.size());
+        print_blanks(blanks, m_out);
+        m_out << s << "   ";
+    }
+    m_out << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_approx_norms() {
+    if (m_core_solver.use_tableau()) return;
+    int blanks = m_title_width + 1 - static_cast<int>(m_approx_norm_title.size());
+    m_out << m_approx_norm_title;
+    print_blanks(blanks, m_out);
+    for (unsigned i = 0; i < ncols(); i++) {
+        string s = T_to_string(m_core_solver.m_column_norms[i]);
+        int blanks = m_column_widths[i] - static_cast<int>(s.size());
+        print_blanks(blanks, m_out);
+        m_out << s << "   ";
+    }
+    m_out << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print() {
+    for (unsigned i = 0; i < nrows(); i++) {
+        print_row(i);
+    }
+    print_bottom_line();
+    print_cost();
+    print_x();
+    print_basis_heading();
+    print_lows();
+    print_upps();
+    print_exact_norms();
+    if (m_core_solver.m_column_norms.size() > 0)
+        print_approx_norms();
+    m_out << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_basis_heading() {
+    int blanks = m_title_width + 1 - static_cast<int>(m_basis_heading_title.size());
+    m_out << m_basis_heading_title;
+    print_blanks(blanks, m_out);
+
+    if (ncols() == 0) {
+        return;
+    }
+    auto bh = m_core_solver.m_basis_heading;
+    for (unsigned i = 0; i < ncols(); i++) {
+        string s = T_to_string(bh[i]);
+        int blanks = m_column_widths[i] - static_cast<unsigned>(s.size());
+        print_blanks(blanks, m_out);
+        m_out << s << "   "; // the column interval
+    }
+    m_out << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_cost() {
+    int blanks = m_title_width + 1 - static_cast<int>(m_cost_title.size());
+    m_out << m_cost_title;
+    print_blanks(blanks, m_out);
+    print_given_rows(m_costs, m_cost_signs, m_core_solver.get_cost());
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_given_rows(vector<string> & row, vector<string> & signs, X rst) {
+    for (unsigned col = 0; col < row.size(); col++) {
+        unsigned width = m_column_widths[col];
+        string s = row[col];
+        int number_of_blanks = width - static_cast<unsigned>(s.size());
+        lean_assert(number_of_blanks >= 0);
+        print_blanks(number_of_blanks, m_out);
+        m_out << s << ' ';
+        if (col < row.size() - 1) {
+            m_out << signs[col + 1] << ' ';
+        }
+    }
+    m_out << '=';
+
+    string rs = T_to_string(rst);
+    int nb = m_rs_width - static_cast<int>(rs.size());
+    lean_assert(nb >= 0);
+    print_blanks(nb + 1, m_out);
+    m_out << rs << std::endl;
+}
+
+template <typename T, typename X> void core_solver_pretty_printer<T, X>::print_row(unsigned i){
+    print_blanks(m_title_width + 1, m_out);
+    auto row = m_A[i];
+    auto sign_row = m_signs[i];
+    auto rs = m_rs[i];
+    print_given_rows(row, sign_row, rs);
+}
+}

src/util/lp/core_solver_pretty_printer_instances.cpp

@@ -0,0 +1,15 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/numeric_pair.h"
+#include "util/lp/core_solver_pretty_printer.hpp"
+template lean::core_solver_pretty_printer<double, double>::core_solver_pretty_printer(lean::lp_core_solver_base<double, double> &, std::ostream & out);
+template void lean::core_solver_pretty_printer<double, double>::print();
+template lean::core_solver_pretty_printer<double, double>::~core_solver_pretty_printer();
+template lean::core_solver_pretty_printer<lean::mpq, lean::mpq>::core_solver_pretty_printer(lean::lp_core_solver_base<lean::mpq, lean::mpq> &, std::ostream & out);
+template void lean::core_solver_pretty_printer<lean::mpq, lean::mpq>::print();
+template lean::core_solver_pretty_printer<lean::mpq, lean::mpq>::~core_solver_pretty_printer();
+template lean::core_solver_pretty_printer<lean::mpq, lean::numeric_pair<lean::mpq> >::core_solver_pretty_printer(lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> > &, std::ostream & out);
+template lean::core_solver_pretty_printer<lean::mpq, lean::numeric_pair<lean::mpq> >::~core_solver_pretty_printer();
+template void lean::core_solver_pretty_printer<lean::mpq, lean::numeric_pair<lean::mpq> >::print();

src/util/lp/dense_matrix.h

@@ -0,0 +1,92 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#ifdef LEAN_DEBUG
+#include "util/vector.h"
+#include "util/lp/matrix.h"
+namespace lean {
+// used for debugging purposes only
+template <typename T, typename X>
+class dense_matrix: public matrix<T, X> {
+public:
+    struct ref {
+        unsigned m_i;
+        dense_matrix & m_s;
+        ref(unsigned i, dense_matrix & s) :m_i(i * s.m_n), m_s(s){}
+        T & operator[] (unsigned j) {
+            return m_s.m_values[m_i + j];
+        }
+        const T & operator[] (unsigned j) const {
+            return m_s.m_v[m_i + j];
+        }
+    };
+    ref operator[] (unsigned i) {
+        return ref(i, *this);
+    }
+    unsigned m_m; // number of rows
+    unsigned m_n; // number of const
+    vector<T> m_values;
+    dense_matrix(unsigned m, unsigned n);
+
+    dense_matrix operator*=(matrix<T, X> const & a) {
+        lean_assert(column_count() == a.row_count());
+        dense_matrix c(row_count(), a.column_count());
+        for (unsigned i = 0; i < row_count(); i++) {
+            for (unsigned j = 0; j < a.column_count(); j++) {
+                T v = numeric_traits<T>::zero();
+                for (unsigned k = 0; k < a.column_count(); k++) {
+                    v += get_elem(i, k) * a(k, j);
+                }
+                c.set_elem(i, j, v);
+            }
+        }
+        *this = c;
+        return *this;
+    }
+
+    dense_matrix & operator=(matrix<T, X> const & other);
+
+    dense_matrix & operator=(dense_matrix const & other);
+
+    dense_matrix(matrix<T, X> const * other);
+    void apply_from_right(T * w);
+
+    void apply_from_right(vector <T> & w);
+
+    T * apply_from_left_with_different_dims(vector<T> &  w);
+    void apply_from_left(vector<T> & w , lp_settings & ) { apply_from_left(w); }
+
+    void apply_from_left(vector<T> & w);
+
+    void apply_from_left(X * w, lp_settings & );
+
+    void apply_from_left_to_X(vector<X> & w, lp_settings & );
+
+    virtual void set_number_of_rows(unsigned /*m*/) {}
+    virtual void set_number_of_columns(unsigned /*n*/) { }
+
+    T get_elem(unsigned i, unsigned j) const { return m_values[i * m_n + j]; }
+
+    unsigned row_count() const { return m_m; }
+    unsigned column_count() const { return m_n; }
+
+    void set_elem(unsigned i, unsigned j, const T& val) {  m_values[i * m_n + j] = val;  }
+
+    // This method pivots row i to row i0 by muliplying row i by
+    //   alpha and adding it to row i0.
+    void pivot_row_to_row(unsigned i, const T& alpha, unsigned i0,
+                          const double & pivot_epsilon);
+
+    void swap_columns(unsigned a, unsigned b);
+
+    void swap_rows(unsigned a, unsigned b);
+
+    void multiply_row_by_constant(unsigned row, T & t);
+
+};
+template <typename T, typename X>
+dense_matrix<T, X> operator* (matrix<T, X> & a, matrix<T, X> & b);
+}
+#endif

src/util/lp/dense_matrix.hpp

@@ -0,0 +1,186 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/lp_settings.h"
+#ifdef LEAN_DEBUG
+#include "util/vector.h"
+#include "util/lp/numeric_pair.h"
+#include "util/lp/dense_matrix.h"
+namespace lean {
+template <typename T> void print_vector(const vector<T> & t, std::ostream & out);
+template <typename T, typename X> dense_matrix<T, X>::dense_matrix(unsigned m, unsigned n) : m_m(m), m_n(n), m_values(m * n, numeric_traits<T>::zero()) {
+}
+
+template <typename T, typename X> dense_matrix<T, X>&
+dense_matrix<T, X>::operator=(matrix<T, X> const & other){
+    if ( this == & other)
+        return *this;
+    m_values = new T[m_m * m_n];
+    for (unsigned i = 0; i < m_m; i ++)
+        for (unsigned j = 0; j < m_n; j++)
+            m_values[i * m_n + j] = other.get_elem(i, j);
+    return *this;
+}
+
+template <typename T, typename X> dense_matrix<T, X>&
+dense_matrix<T, X>::operator=(dense_matrix const & other){
+    if ( this == & other)
+        return *this;
+    m_m = other.m_m;
+    m_n = other.m_n;
+    m_values.resize(m_m * m_n);
+    for (unsigned i = 0; i < m_m; i ++)
+        for (unsigned j = 0; j < m_n; j++)
+            m_values[i * m_n + j] = other.get_elem(i, j);
+    return *this;
+}
+
+template <typename T, typename X> dense_matrix<T, X>::dense_matrix(matrix<T, X> const * other) :
+    m_m(other->row_count()),
+    m_n(other->column_count()) {
+    m_values.resize(m_m*m_n);
+    for (unsigned i = 0; i < m_m; i++)
+        for (unsigned j = 0; j < m_n; j++)
+            m_values[i * m_n + j] = other->get_elem(i, j);
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::apply_from_right(T * w) {
+    T * t = new T[m_m];
+    for (int i = 0; i < m_m; i ++) {
+        T v = numeric_traits<T>::zero();
+        for (int j = 0; j < m_m; j++) {
+            v += w[j]* get_elem(j, i);
+        }
+        t[i] = v;
+    }
+
+    for (int i = 0; i < m_m; i++) {
+        w[i] = t[i];
+    }
+    delete [] t;
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::apply_from_right(vector <T> & w) {
+    vector<T> t(m_m, numeric_traits<T>::zero());
+    for (unsigned i = 0; i < m_m; i ++) {
+        auto & v = t[i];
+        for (unsigned j = 0; j < m_m; j++)
+            v += w[j]* get_elem(j, i);
+    }
+
+    for (unsigned i = 0; i < m_m; i++)
+        w[i] = t[i];
+}
+
+template <typename T, typename X> T* dense_matrix<T, X>::
+apply_from_left_with_different_dims(vector<T> &  w) {
+    T * t = new T[m_m];
+    for (int i = 0; i < m_m; i ++) {
+        T v = numeric_traits<T>::zero();
+        for (int j = 0; j < m_n; j++) {
+            v += w[j]* get_elem(i, j);
+        }
+        t[i] = v;
+    }
+
+    return t;
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::apply_from_left(vector<T> & w) {
+    T * t = new T[m_m];
+    for (unsigned i = 0; i < m_m; i ++) {
+        T v = numeric_traits<T>::zero();
+        for (unsigned j = 0; j < m_m; j++) {
+            v += w[j]* get_elem(i, j);
+        }
+        t[i] = v;
+    }
+
+    for (unsigned i = 0; i < m_m; i ++) {
+        w[i] = t[i];
+    }
+    delete [] t;
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::apply_from_left(X * w, lp_settings & ) {
+    T * t = new T[m_m];
+    for (int i = 0; i < m_m; i ++) {
+        T v = numeric_traits<T>::zero();
+        for (int j = 0; j < m_m; j++) {
+            v += w[j]* get_elem(i, j);
+        }
+        t[i] = v;
+    }
+
+    for (int i = 0; i < m_m; i ++) {
+        w[i] = t[i];
+    }
+    delete [] t;
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::apply_from_left_to_X(vector<X> & w, lp_settings & ) {
+    vector<X> t(m_m);
+    for (int i = 0; i < m_m; i ++) {
+        X v = zero_of_type<X>();
+        for (int j = 0; j < m_m; j++) {
+            v += w[j]* get_elem(i, j);
+        }
+        t[i] = v;
+    }
+
+    for (int i = 0; i < m_m; i ++) {
+        w[i] = t[i];
+    }
+}
+
+// This method pivots row i to row i0 by muliplying row i by
+//   alpha and adding it to row i0.
+template <typename T, typename X> void dense_matrix<T, X>::pivot_row_to_row(unsigned i, const T& alpha, unsigned i0,
+                                                                            const double & pivot_epsilon) {
+    for (unsigned j = 0; j < m_n; j++) {
+        m_values[i0 * m_n + j] += m_values[i * m_n + j] * alpha;
+        if (fabs(m_values[i0 + m_n + j]) < pivot_epsilon) {
+            m_values[i0 + m_n + j] = numeric_traits<T>::zero();;
+        }
+    }
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::swap_columns(unsigned a, unsigned b) {
+    for (unsigned i = 0; i < m_m; i++) {
+        T t = get_elem(i, a);
+        set_elem(i, a, get_elem(i, b));
+        set_elem(i, b, t);
+    }
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::swap_rows(unsigned a, unsigned b) {
+    for (unsigned i = 0; i < m_n; i++) {
+        T t = get_elem(a, i);
+        set_elem(a, i, get_elem(b, i));
+        set_elem(b, i, t);
+    }
+}
+
+template <typename T, typename X> void dense_matrix<T, X>::multiply_row_by_constant(unsigned row, T & t) {
+    for (unsigned i = 0; i < m_n; i++) {
+        set_elem(row, i, t * get_elem(row, i));
+    }
+}
+
+template <typename T, typename X>
+dense_matrix<T, X> operator* (matrix<T, X> & a, matrix<T, X> & b){
+    lean_assert(a.column_count() == b.row_count());
+    dense_matrix<T, X> ret(a.row_count(), b.column_count());
+    for (unsigned i = 0; i < ret.m_m; i++)
+        for (unsigned j = 0; j< ret.m_n; j++) {
+            T v = numeric_traits<T>::zero();
+            for (unsigned k = 0; k < a.column_count(); k ++){
+                v += (a.get_elem(i, k) * b.get_elem(k, j));
+            }
+            ret.set_elem(i, j, v);
+        }
+    return  ret;
+}
+}
+#endif

src/util/lp/dense_matrix_instances.cpp

@@ -0,0 +1,24 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/lp_settings.h"
+#include "util/lp/dense_matrix.hpp"
+#ifdef LEAN_DEBUG
+#include "util/vector.h"
+template lean::dense_matrix<double, double> lean::operator*<double, double>(lean::matrix<double, double>&, lean::matrix<double, double>&);
+template void lean::dense_matrix<double, double>::apply_from_left(vector<double> &);
+template lean::dense_matrix<double, double>::dense_matrix(lean::matrix<double, double> const*);
+template lean::dense_matrix<double, double>::dense_matrix(unsigned int, unsigned int);
+template lean::dense_matrix<double, double>& lean::dense_matrix<double, double>::operator=(lean::dense_matrix<double, double> const&);
+template lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::dense_matrix(lean::matrix<lean::mpq, lean::numeric_pair<lean::mpq> > const*);
+template void lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::apply_from_left(vector<lean::mpq>&);
+template lean::dense_matrix<lean::mpq, lean::mpq> lean::operator*<lean::mpq, lean::mpq>(lean::matrix<lean::mpq, lean::mpq>&, lean::matrix<lean::mpq, lean::mpq>&);
+template lean::dense_matrix<lean::mpq, lean::mpq> & lean::dense_matrix<lean::mpq, lean::mpq>::operator=(lean::dense_matrix<lean::mpq, lean::mpq> const&);
+template lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::dense_matrix(unsigned int, unsigned int);
+template lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >& lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::operator=(lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> > const&);
+template lean::dense_matrix<lean::mpq, lean::numeric_pair<lean::mpq> > lean::operator*<lean::mpq, lean::numeric_pair<lean::mpq> >(lean::matrix<lean::mpq, lean::numeric_pair<lean::mpq> >&, lean::matrix<lean::mpq, lean::numeric_pair<lean::mpq> >&);
+template void lean::dense_matrix<lean::mpq, lean::numeric_pair< lean::mpq> >::apply_from_right( vector< lean::mpq> &);
+template void lean::dense_matrix<double,double>::apply_from_right(class vector<double> &);
+template void lean::dense_matrix<lean::mpq, lean::mpq>::apply_from_left(vector<lean::mpq>&);
+#endif

src/util/lp/eta_matrix.h

@@ -0,0 +1,83 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include "util/lp/tail_matrix.h"
+#include "util/lp/permutation_matrix.h"
+namespace lean {
+
+// This is the sum of a unit matrix and a one-column matrix
+template <typename T, typename X>
+class eta_matrix
+    : public tail_matrix<T, X> {
+#ifdef LEAN_DEBUG
+    unsigned m_length;
+#endif
+    unsigned m_column_index;
+public:
+    sparse_vector<T> m_column_vector;
+    T m_diagonal_element;
+#ifdef LEAN_DEBUG
+    eta_matrix(unsigned column_index, unsigned length):
+#else
+        eta_matrix(unsigned column_index):
+#endif
+
+#ifdef LEAN_DEBUG
+        m_length(length),
+#endif
+        m_column_index(column_index) {}
+
+    bool is_dense() const { return false; }
+
+    void print(std::ostream & out) {
+        print_matrix(*this, out);
+    }
+
+    bool is_unit() {
+        return m_column_vector.size() == 0 && m_diagonal_element == 1;
+    }
+
+    bool set_diagonal_element(T const & diagonal_element) {
+        m_diagonal_element = diagonal_element;
+        return !lp_settings::is_eps_small_general(diagonal_element, 1e-12);
+    }
+
+    const T & get_diagonal_element() const {
+        return m_diagonal_element;
+    }
+
+    void apply_from_left(vector<X> & w, lp_settings & );
+
+    template <typename L>
+    void apply_from_left_local(indexed_vector<L> & w, lp_settings & settings);
+
+    void apply_from_left_to_T(indexed_vector<T> & w, lp_settings & settings) {
+        apply_from_left_local(w, settings);
+    }
+
+
+    void push_back(unsigned row_index, T val ) {
+        lean_assert(row_index != m_column_index);
+        m_column_vector.push_back(row_index, val);
+    }
+
+    void apply_from_right(vector<T> & w);
+    void apply_from_right(indexed_vector<T> & w);
+
+    T get_elem(unsigned i, unsigned j) const;
+#ifdef LEAN_DEBUG
+    unsigned row_count() const { return m_length; }
+    unsigned column_count() const { return m_length; }
+    void set_number_of_rows(unsigned m) { m_length = m; }
+    void set_number_of_columns(unsigned n) { m_length = n; }
+#endif
+    void divide_by_diagonal_element() {
+        m_column_vector.divide(m_diagonal_element);
+    }
+    void conjugate_by_permutation(permutation_matrix<T, X> & p);
+};
+}

src/util/lp/eta_matrix.hpp

@@ -0,0 +1,136 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include "util/lp/eta_matrix.h"
+namespace lean {
+
+// This is the sum of a unit matrix and a one-column matrix
+template <typename T, typename X>
+void eta_matrix<T, X>::apply_from_left(vector<X> & w, lp_settings & ) {
+    auto & w_at_column_index = w[m_column_index];
+    for (auto & it : m_column_vector.m_data) {
+        w[it.first] += w_at_column_index * it.second;
+    }
+    w_at_column_index /= m_diagonal_element;
+}
+template <typename T, typename X>
+template <typename L>
+void eta_matrix<T, X>::
+apply_from_left_local(indexed_vector<L> & w, lp_settings & settings) {
+    const L w_at_column_index = w[m_column_index];
+    if (is_zero(w_at_column_index)) return;
+
+    if (settings.abs_val_is_smaller_than_drop_tolerance(w[m_column_index] /= m_diagonal_element)) {
+        w[m_column_index] = zero_of_type<L>();
+        w.erase_from_index(m_column_index);
+    }
+
+    for (auto & it : m_column_vector.m_data) {
+        unsigned i = it.first;
+        if (is_zero(w[i])) {
+            L v = w[i] = w_at_column_index * it.second;
+            if (settings.abs_val_is_smaller_than_drop_tolerance(v)) {
+                w[i] = zero_of_type<L>();
+                continue;
+            }
+            w.m_index.push_back(i);
+        } else  {
+            L v = w[i] += w_at_column_index * it.second;
+            if (settings.abs_val_is_smaller_than_drop_tolerance(v)) {
+                w[i] = zero_of_type<L>();
+                w.erase_from_index(i);
+            }
+        }
+    }
+}
+template <typename T, typename X>
+void eta_matrix<T, X>::apply_from_right(vector<T> & w) {
+#ifdef LEAN_DEBUG
+    // dense_matrix<T, X> deb(*this);
+    // auto clone_w = clone_vector<T>(w, get_number_of_rows());
+    // deb.apply_from_right(clone_w);
+#endif
+    T t = w[m_column_index] / m_diagonal_element;
+    for (auto & it : m_column_vector.m_data) {
+        t += w[it.first] * it.second;
+    }
+    w[m_column_index] = t;
+#ifdef LEAN_DEBUG
+    // lean_assert(vectors_are_equal<T>(clone_w, w, get_number_of_rows()));
+    // delete clone_w;
+#endif
+}
+template <typename T, typename X>
+void eta_matrix<T, X>::apply_from_right(indexed_vector<T> & w) {
+    if (w.m_index.size() == 0)
+        return;
+#ifdef LEAN_DEBUG
+    // vector<T> wcopy(w.m_data);
+    // apply_from_right(wcopy);
+#endif
+    T & t = w[m_column_index];
+    t /= m_diagonal_element;
+    bool was_in_index = (!numeric_traits<T>::is_zero(t));
+    
+    for (auto & it : m_column_vector.m_data) {
+        t += w[it.first] * it.second;
+    }
+
+    if (numeric_traits<T>::precise() ) {
+        if (!numeric_traits<T>::is_zero(t)) {
+            if (!was_in_index)
+                w.m_index.push_back(m_column_index);
+        } else {
+            if (was_in_index)
+                w.erase_from_index(m_column_index);
+        }
+    } else {
+        if (!lp_settings::is_eps_small_general(t, 1e-14)) {
+            if (!was_in_index)
+                w.m_index.push_back(m_column_index);
+        } else {
+            if (was_in_index)
+                w.erase_from_index(m_column_index);
+            t = zero_of_type<T>();
+        }
+    }
+    
+#ifdef LEAN_DEBUG
+    // lean_assert(w.is_OK());
+    // lean_assert(vectors_are_equal<T>(wcopy, w.m_data));
+#endif
+}
+#ifdef LEAN_DEBUG
+template <typename T, typename X>
+T eta_matrix<T, X>::get_elem(unsigned i, unsigned j) const {
+    if (j == m_column_index){
+        if (i == j) {
+            return 1 / m_diagonal_element;
+        }
+        return m_column_vector[i];
+    }
+
+    return i == j ? numeric_traits<T>::one() : numeric_traits<T>::zero();
+}
+#endif
+template <typename T, typename X>
+void eta_matrix<T, X>::conjugate_by_permutation(permutation_matrix<T, X> & p) {
+    // this = p * this * p(-1)
+#ifdef LEAN_DEBUG
+    // auto rev = p.get_reverse();
+    // auto deb = ((*this) * rev);
+    // deb = p * deb;
+#endif
+    m_column_index = p.get_rev(m_column_index);
+    for (auto & pair : m_column_vector.m_data) {
+        pair.first = p.get_rev(pair.first);
+    }
+#ifdef LEAN_DEBUG
+    // lean_assert(deb == *this);
+#endif
+}
+}

src/util/lp/eta_matrix_instances.cpp

@@ -0,0 +1,28 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <memory>
+#include "util/vector.h"
+#include "util/lp/numeric_pair.h"
+#include "util/lp/eta_matrix.hpp"
+#ifdef LEAN_DEBUG
+template double lean::eta_matrix<double, double>::get_elem(unsigned int, unsigned int) const;
+template lean::mpq lean::eta_matrix<lean::mpq, lean::mpq>::get_elem(unsigned int, unsigned int) const;
+template lean::mpq lean::eta_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::get_elem(unsigned int, unsigned int) const;
+#endif
+template void lean::eta_matrix<double, double>::apply_from_left(vector<double>&, lean::lp_settings&);
+template void lean::eta_matrix<double, double>::apply_from_right(vector<double>&);
+template void lean::eta_matrix<double, double>::conjugate_by_permutation(lean::permutation_matrix<double, double>&);
+template void lean::eta_matrix<lean::mpq, lean::mpq>::apply_from_left(vector<lean::mpq>&, lean::lp_settings&);
+template void lean::eta_matrix<lean::mpq, lean::mpq>::apply_from_right(vector<lean::mpq>&);
+template void lean::eta_matrix<lean::mpq, lean::mpq>::conjugate_by_permutation(lean::permutation_matrix<lean::mpq, lean::mpq>&);
+template void lean::eta_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::apply_from_left(vector<lean::numeric_pair<lean::mpq> >&, lean::lp_settings&);
+template void lean::eta_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::apply_from_right(vector<lean::mpq>&);
+template void lean::eta_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::conjugate_by_permutation(lean::permutation_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >&);
+template void lean::eta_matrix<double, double>::apply_from_left_local<double>(lean::indexed_vector<double>&, lean::lp_settings&);
+template void lean::eta_matrix<lean::mpq, lean::mpq>::apply_from_left_local<lean::mpq>(lean::indexed_vector<lean::mpq>&, lean::lp_settings&);
+template void lean::eta_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::apply_from_left_local<lean::mpq>(lean::indexed_vector<lean::mpq>&, lean::lp_settings&);
+template void lean::eta_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >::apply_from_right(lean::indexed_vector<lean::mpq>&);
+template void lean::eta_matrix<lean::mpq, lean::mpq>::apply_from_right(lean::indexed_vector<lean::mpq>&);
+template void lean::eta_matrix<double, double>::apply_from_right(lean::indexed_vector<double>&);

src/util/lp/hash_helper.h

@@ -0,0 +1,39 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include <utility>
+#include <functional>
+#include "util/numerics/mpq.h"
+#ifdef __CLANG__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wmismatched-tags"
+#endif
+namespace std {
+template<>
+struct hash<lean::mpq> {
+    inline size_t operator()(const lean::mpq & v) const {
+        return v.hash();
+    }
+};
+}
+
+template <class T>
+inline void hash_combine(std::size_t & seed, const T & v) {
+    seed ^= std::hash<T>()(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+}
+
+namespace std {
+template<typename S, typename T> struct hash<pair<S, T>> {
+    inline size_t operator()(const pair<S, T> & v) const {
+        size_t seed = 0;
+        hash_combine(seed, v.first);
+        hash_combine(seed, v.second);
+        return seed;
+    }
+};
+}
+#ifdef __CLANG__
+#pragma clang diagnostic pop
+#endif

src/util/lp/implied_bound.h

@@ -0,0 +1,42 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/lp_settings.h"
+#include "util/lp/lar_constraints.h"
+namespace lean {
+struct implied_bound {
+    mpq m_bound;
+    unsigned m_j; // the column for which the bound has been found
+    bool m_is_low_bound;
+    bool m_coeff_before_j_is_pos;
+    unsigned m_row_or_term_index;
+    bool m_strict;
+    
+    lconstraint_kind kind() const {
+        lconstraint_kind k = m_is_low_bound? GE : LE;
+        if (m_strict)
+            k = static_cast<lconstraint_kind>(k / 2);
+        return k;
+    }
+    bool operator==(const implied_bound & o) const {
+        return m_j == o.m_j && m_is_low_bound == o.m_is_low_bound && m_bound == o.m_bound &&
+            m_coeff_before_j_is_pos == o.m_coeff_before_j_is_pos &&
+            m_row_or_term_index == o.m_row_or_term_index && m_strict == o.m_strict;
+    }
+    implied_bound(){}
+    implied_bound(const mpq & a,
+                  unsigned j,
+                  bool low_bound,
+                  bool coeff_before_j_is_pos,
+                  unsigned row_or_term_index,
+                  bool strict):
+        m_bound(a),
+        m_j(j),
+        m_is_low_bound(low_bound),
+        m_coeff_before_j_is_pos(coeff_before_j_is_pos),
+        m_row_or_term_index(row_or_term_index),
+        m_strict(strict) {}
+};
+}

src/util/lp/indexed_value.h

@@ -0,0 +1,55 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+
+namespace lean {
+template <typename T>
+class indexed_value {
+public:
+    T m_value;
+    // the idea is that m_index for a row element gives its column, and for a column element its row
+    unsigned m_index;
+    // m_other point is the offset of the corresponding element in its vector : for a row element it point to the column element offset,
+    // for a column element it points to the row element offset
+    unsigned m_other;
+    indexed_value() {}
+    indexed_value(T v, unsigned i) : m_value(v), m_index(i) {}
+    indexed_value(T v, unsigned i, unsigned other) :
+        m_value(v), m_index(i), m_other(other) {
+    }
+
+    indexed_value(const indexed_value & iv) {
+        m_value = iv.m_value;
+        m_index = iv.m_index;
+        m_other = iv.m_other;
+    }
+
+    indexed_value & operator=(const indexed_value & right_side) {
+        m_value = right_side.m_value;
+        m_index = right_side.m_index;
+        m_other = right_side.m_other;
+        return *this;
+    }
+
+    const T & value() const {
+        return m_value;
+    }
+
+    void set_value(T val) {
+        m_value = val;
+    }
+};
+#ifdef LEAN_DEBUG
+template <typename X>
+bool check_vector_for_small_values(indexed_vector<X> & w, lp_settings & settings) {
+    for (unsigned i : w.m_index) {
+        const X & v = w[i];
+        if ((!is_zero(v)) && settings.abs_val_is_smaller_than_drop_tolerance(v))
+            return false;
+    }
+    return true;
+}
+#endif
+}

src/util/lp/indexed_vector.h

@@ -0,0 +1,169 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include "util/debug.h"
+#include <string>
+#include <iomanip>
+#include "util/lp/lp_utils.h"
+#include "util/lp/lp_settings.h"
+#include <unordered_set>
+namespace lean {
+
+template <typename T> void print_vector(const vector<T> & t, std::ostream & out);
+template <typename T> void print_vector(const buffer<T> & t, std::ostream & out);
+template <typename T> void print_sparse_vector(const vector<T> & t, std::ostream & out);
+
+void print_vector(const vector<mpq> & t, std::ostream & out);
+template <typename T>
+class indexed_vector {
+public:
+    // m_index points to non-zero elements of m_data
+    vector<T> m_data;
+    vector<unsigned> m_index;
+    indexed_vector(unsigned data_size) {
+        m_data.resize(data_size, numeric_traits<T>::zero());
+    }
+
+    indexed_vector& operator=(const indexed_vector<T>& y) {
+        for (unsigned i: m_index)
+            m_data[i] = zero_of_type<T>();
+
+        m_index = y.m_index;
+
+        m_data.resize(y.data_size());
+        for (unsigned i : m_index)
+            m_data[i] = y[i];
+        return *this;
+    }
+
+    bool operator==(const indexed_vector<T>& y) const {
+        std::unordered_set<unsigned> y_index;
+        for (unsigned i : y.m_index)
+            y_index.insert(i);
+
+        std::unordered_set<unsigned> this_index;
+        for (unsigned i : m_index)
+            this_index.insert(i);
+
+        for (unsigned i : y.m_index) {
+            if (this_index.find(i) == this_index.end())
+                return false;
+        }
+           
+        for (unsigned i : m_index) {
+            if (y_index.find(i) == y_index.end())
+                return false;
+        }
+
+        return vectors_are_equal(m_data, m_data);
+
+    }
+
+    indexed_vector() {}
+
+    void resize(unsigned data_size);
+    unsigned data_size() const {
+        return m_data.size();
+    }
+
+    unsigned size() {
+        return m_index.size();
+    }
+
+    void set_value(const T& value, unsigned index);
+    void set_value_as_in_dictionary(unsigned index) {
+        lean_assert(index < m_data.size());
+        T & loc = m_data[index];
+        if (is_zero(loc)) {
+            m_index.push_back(index);
+            loc = one_of_type<T>(); // use as a characteristic function
+        } 
+    }
+    
+
+    void clear();
+    void clear_all();
+    const T& operator[] (unsigned i) const {
+        return m_data[i];
+    }
+
+    T& operator[] (unsigned i)  {
+        return m_data[i];
+    }
+
+    void clean_up() {
+#if 0==1
+        for (unsigned k = 0; k < m_index.size(); k++) {
+            unsigned i = m_index[k];
+            T & v = m_data[i];
+            if (lp_settings::is_eps_small_general(v, 1e-14)) {
+                v = zero_of_type<T>();
+                m_index.erase(m_index.begin() + k--);
+            }
+        }
+#endif
+       vector<unsigned> index_copy;
+       for (unsigned i : m_index) {
+           T & v = m_data[i];
+           if (!lp_settings::is_eps_small_general(v, 1e-14)) {
+               index_copy.push_back(i);
+           } else if (!numeric_traits<T>::is_zero(v)) {
+               v = zero_of_type<T>();
+           }
+       }
+       m_index = index_copy;
+    }
+
+    
+    void erase_from_index(unsigned j);
+
+    void add_value_at_index_with_drop_tolerance(unsigned j, const T& val_to_add) {
+        T & v = m_data[j];
+        bool was_zero = is_zero(v);
+        v += val_to_add;
+        if (lp_settings::is_eps_small_general(v, 1e-14)) {
+            v = zero_of_type<T>();
+            if (!was_zero) {
+                erase_from_index(j);
+            }
+        } else {
+            if (was_zero)
+                m_index.push_back(j);
+        }
+    }
+
+    void add_value_at_index(unsigned j, const T& val_to_add) {
+        T & v = m_data[j];
+        bool was_zero = is_zero(v);
+        v += val_to_add;
+        if (is_zero(v)) {
+            if (!was_zero)
+                erase_from_index(j);
+        } else {
+            if (was_zero)
+                m_index.push_back(j);
+        }
+    }
+
+    void restore_index_and_clean_from_data() {
+        m_index.resize(0);
+        for (unsigned i = 0; i < m_data.size(); i++) {
+            T & v = m_data[i];
+            if (lp_settings::is_eps_small_general(v, 1e-14)) {
+                v = zero_of_type<T>();
+            } else {
+                m_index.push_back(i);
+            }
+        }
+    }
+    
+#ifdef LEAN_DEBUG
+    bool is_OK() const;
+    void print(std::ostream & out);
+#endif
+};
+}

src/util/lp/indexed_vector.hpp

@@ -0,0 +1,110 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/vector.h"
+#include "util/lp/indexed_vector.h"
+#include "util/lp/lp_settings.h"
+namespace lean {
+
+template <typename T>
+void print_vector(const vector<T> & t, std::ostream & out) {
+    for (unsigned i = 0; i < t.size(); i++)
+        out << t[i] << " ";
+    out << std::endl;
+}
+
+
+template <typename T>
+void print_vector(const buffer<T> & t, std::ostream & out) {
+    for (unsigned i = 0; i < t.size(); i++)
+        out << t[i] << " ";
+    out << std::endl;
+}
+
+template <typename T>
+void print_sparse_vector(const vector<T> & t, std::ostream & out) {
+    for (unsigned i = 0; i < t.size(); i++) {
+        if (is_zero(t[i]))continue;
+        out << "[" << i << "] = " << t[i] << ", ";
+    }
+    out << std::endl;
+}
+
+void print_vector(const vector<mpq> & t, std::ostream & out) {
+    for (unsigned i = 0; i < t.size(); i++)
+        out << t[i].get_double() << std::setprecision(3) << " ";
+    out << std::endl;
+}
+
+template <typename T>
+void indexed_vector<T>::resize(unsigned data_size) {
+    clear();
+    m_data.resize(data_size, numeric_traits<T>::zero());
+    lean_assert(is_OK());
+}
+
+template <typename T>
+void indexed_vector<T>::set_value(const T& value, unsigned index) {
+    m_data[index] = value;
+    lean_assert(std::find(m_index.begin(), m_index.end(), index) == m_index.end());
+    m_index.push_back(index);
+}
+
+template <typename T>
+void indexed_vector<T>::clear() {
+    for (unsigned i : m_index)
+        m_data[i] = numeric_traits<T>::zero();
+    m_index.resize(0);
+}
+template <typename T>
+void indexed_vector<T>::clear_all() {
+    unsigned i = m_data.size();
+    while (i--)  m_data[i] = numeric_traits<T>::zero();
+    m_index.resize(0);
+}
+template <typename T>
+void indexed_vector<T>::erase_from_index(unsigned j) {
+    auto it = std::find(m_index.begin(), m_index.end(), j);
+    if (it != m_index.end())
+        m_index.erase(it);
+}
+
+#ifdef LEAN_DEBUG
+template <typename T>
+bool indexed_vector<T>::is_OK() const {
+    return true;
+    const double drop_eps = 1e-14;
+    for (unsigned i = 0; i < m_data.size(); i++) {
+        if (!is_zero(m_data[i]) && lp_settings::is_eps_small_general(m_data[i], drop_eps)) {
+            return false;
+        }
+        if (lp_settings::is_eps_small_general(m_data[i], drop_eps) != (std::find(m_index.begin(), m_index.end(), i) == m_index.end())) {
+            return false;
+        }
+    }
+
+    std::unordered_set<unsigned> s;
+    for (unsigned i : m_index) {
+        //no duplicates!!!
+        if (s.find(i) != s.end())
+            return false;
+        s.insert(i);
+        if (i >= m_data.size())
+            return false;
+    }
+
+    return true;
+}
+template <typename T>
+void indexed_vector<T>::print(std::ostream & out) {
+    out << "m_index " << std::endl;
+    for (unsigned i = 0; i < m_index.size(); i++) {
+        out << m_index[i] << " ";
+    }
+    out << std::endl;
+    print_vector(m_data, out);
+}
+#endif
+
+}

src/util/lp/indexed_vector_instances.cpp

@@ -0,0 +1,36 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/vector.h"
+#include "util/lp/indexed_vector.hpp"
+namespace lean {
+template void indexed_vector<double>::clear();
+template void indexed_vector<double>::clear_all();
+template void indexed_vector<double>::erase_from_index(unsigned int);
+template void indexed_vector<double>::set_value(const double&, unsigned int);
+template void indexed_vector<mpq>::clear();
+template void indexed_vector<unsigned>::clear();
+template void indexed_vector<mpq>::clear_all();
+template void indexed_vector<mpq>::erase_from_index(unsigned int);
+template void indexed_vector<mpq>::resize(unsigned int);
+template void indexed_vector<unsigned>::resize(unsigned int);
+template void indexed_vector<mpq>::set_value(const mpq&, unsigned int);
+template void indexed_vector<unsigned>::set_value(const unsigned&, unsigned int);
+#ifdef LEAN_DEBUG
+template bool indexed_vector<double>::is_OK() const;
+template bool indexed_vector<mpq>::is_OK() const;
+template bool indexed_vector<lean::numeric_pair<mpq> >::is_OK() const;
+template void lean::indexed_vector< lean::mpq>::print(std::basic_ostream<char,struct std::char_traits<char> > &);
+template void lean::indexed_vector<double>::print(std::basic_ostream<char,struct std::char_traits<char> > &);
+template void lean::indexed_vector<lean::numeric_pair<lean::mpq> >::print(std::ostream&);
+#endif
+}
+template void lean::print_vector<double>(vector<double> const&, std::ostream&);
+template void lean::print_vector<unsigned int>(vector<unsigned int> const&, std::ostream&);
+template void lean::print_vector<std::string>(vector<std::string> const&, std::ostream&);
+template void lean::print_vector<lean::numeric_pair<lean::mpq> >(vector<lean::numeric_pair<lean::mpq>> const&, std::ostream&);
+template void lean::indexed_vector<double>::resize(unsigned int);
+template void lean::print_vector< lean::mpq>(vector< lean::mpq> const &, std::basic_ostream<char, std::char_traits<char> > &);
+template void lean::print_vector<std::pair<lean::mpq, unsigned int> >(vector<std::pair<lean::mpq, unsigned int>> const&, std::ostream&);
+template void lean::indexed_vector<lean::numeric_pair<lean::mpq> >::erase_from_index(unsigned int);

src/util/lp/int_set.h

@@ -0,0 +1,66 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/vector.h"
+#include "util/lp/indexed_vector.h"
+#include <ostream>
+namespace lean {
+// serves at a set of non-negative integers smaller than the set size
+class int_set {
+    vector<int> m_data;
+public:
+    vector<int> m_index;
+    int_set(unsigned size): m_data(size, -1) {}
+    int_set() {}
+    bool contains(unsigned j) const {
+        if (j >= m_data.size())
+            return false;
+        return m_data[j] >= 0;
+    }
+    void insert(unsigned j) {
+        lean_assert(j < m_data.size());
+        if (contains(j)) return;
+        m_data[j] = m_index.size();
+        m_index.push_back(j);
+    }
+    void erase(unsigned j) {
+        if (!contains(j)) return;
+        unsigned pos_j = m_data[j];
+        unsigned last_pos = m_index.size() - 1;
+        int last_j = m_index[last_pos];
+        if (last_pos != pos_j) {
+            // move last to j spot
+            m_data[last_j] = pos_j;
+            m_index[pos_j] = last_j;
+        }
+        m_index.pop_back();
+        m_data[j] = -1;
+    }
+
+    void resize(unsigned size) {
+        m_data.resize(size, -1);
+    }
+
+    void increase_size_by_one() {
+        resize(m_data.size() + 1);
+    }
+
+    unsigned data_size() const {  return m_data.size(); }
+    unsigned size() const { return m_index.size();}
+    bool is_empty() const { return size() == 0; }
+    void clear() {
+        for (unsigned j : m_index)
+            m_data[j] = -1;
+        m_index.resize(0);
+    }
+    void print(std::ostream & out ) const {
+        for (unsigned j : m_index) {
+            out << j << " ";
+        }
+        out << std::endl;
+    }
+    
+};
+}

src/util/lp/iterator_on_column.h

@@ -0,0 +1,50 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/linear_combination_iterator.h"
+#include "util/lp/static_matrix.h"
+#include "util/lp/lar_term.h"
+namespace lean {
+template <typename T, typename X>
+struct iterator_on_column:linear_combination_iterator<T> {
+    const vector<column_cell>& m_column; // the offset in term coeffs
+    const static_matrix<T, X> & m_A;
+    int m_i = -1; // the initial offset in the column
+    unsigned size() const { return m_column.size(); }
+    iterator_on_column(const vector<column_cell>& column, const static_matrix<T,X> & A) // the offset in term coeffs
+        :
+        m_column(column),
+        m_A(A),
+        m_i(-1) {}
+    
+    bool next(mpq & a, unsigned & i) {
+        if (++m_i >= static_cast<int>(m_column.size()))
+            return false;
+
+        const column_cell& c = m_column[m_i];
+        a = m_A.get_val(c);
+        i = c.m_i;
+        return true;
+    }
+
+    bool next(unsigned & i) {
+        if (++m_i >= static_cast<int>(m_column.size()))
+            return false;
+
+        const column_cell& c = m_column[m_i];
+        i = c.m_i;
+        return true;
+    }
+    
+    void reset() {
+        m_i = -1;
+    }
+
+    linear_combination_iterator<mpq> * clone() {
+        iterator_on_column * r = new iterator_on_column(m_column, m_A);
+        return r;
+    }
+};
+}

src/util/lp/iterator_on_indexed_vector.h

@@ -0,0 +1,35 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/linear_combination_iterator.h"
+namespace lean {
+template <typename T>
+struct iterator_on_indexed_vector:linear_combination_iterator<T> {
+    const indexed_vector<T> & m_v;
+    unsigned m_offset = 0;
+    iterator_on_indexed_vector(const indexed_vector<T> & v) : m_v(v){}
+    unsigned size() const { return m_v.m_index.size(); }
+    bool next(T & a, unsigned & i) {
+        if (m_offset >= m_v.m_index.size())
+            return false;
+        i = m_v.m_index[m_offset++];
+        a = m_v.m_data[i];
+        return true;
+    }
+    
+    bool next(unsigned & i) {
+        if (m_offset >= m_v.m_index.size())
+            return false;
+        i = m_v.m_index[m_offset++];
+        return true;
+    }
+    void reset() {
+        m_offset = 0;
+    }
+    linear_combination_iterator<T>* clone() {
+        return new iterator_on_indexed_vector(m_v);
+    }
+};
+}

src/util/lp/iterator_on_pivot_row.h

@@ -0,0 +1,42 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/iterator_on_indexed_vector.h"
+namespace lean {
+template <typename T>
+struct iterator_on_pivot_row:linear_combination_iterator<T> {
+    bool m_basis_returned = false;
+    const indexed_vector<T> & m_v;
+    unsigned m_basis_j;
+    iterator_on_indexed_vector<T> m_it;
+    unsigned size() const { return m_it.size(); }
+    iterator_on_pivot_row(const indexed_vector<T> & v, unsigned basis_j) : m_v(v), m_basis_j(basis_j), m_it(v) {}
+    bool next(T & a, unsigned & i) {
+        if (m_basis_returned == false) {
+            m_basis_returned = true;
+            a = one_of_type<T>();
+            i = m_basis_j;
+            return true;
+        }
+        return m_it.next(a, i);
+    }
+    bool next(unsigned & i) {
+        if (m_basis_returned == false) {
+            m_basis_returned = true;
+            i = m_basis_j;
+            return true;
+        }
+        return m_it.next(i);
+    }
+    void reset() {
+        m_basis_returned = false;
+        m_it.reset();
+    }
+    linear_combination_iterator<T> * clone() {
+        iterator_on_pivot_row * r = new iterator_on_pivot_row(m_v, m_basis_j);
+        return r;
+    }
+};
+}

src/util/lp/iterator_on_row.h

@@ -0,0 +1,37 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/linear_combination_iterator.h"
+namespace lean {
+template <typename T>
+struct iterator_on_row:linear_combination_iterator<T> {
+    const vector<row_cell<T>> & m_row;
+    unsigned m_i= 0; // offset
+    iterator_on_row(const vector<row_cell<T>> & row) : m_row(row)
+    {}
+    unsigned size() const { return m_row.size(); }
+    bool next(T & a, unsigned & i) {
+        if (m_i == m_row.size())
+            return false;
+        auto &c = m_row[m_i++];
+        i = c.m_j;
+        a = c.get_val();
+        return true;
+    }
+    bool next(unsigned & i) {
+        if (m_i == m_row.size())
+            return false;
+        auto &c = m_row[m_i++];
+        i = c.m_j;
+        return true;
+    }
+    void reset() {
+        m_i = 0;
+    }
+    linear_combination_iterator<T>* clone() {
+        return new iterator_on_row(m_row);
+    }
+};
+}

src/util/lp/iterator_on_term_with_basis_var.h

@@ -0,0 +1,56 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/linear_combination_iterator.h"
+#include "util/lp/numeric_pair.h"
+#include "util/lp/lar_term.h"
+namespace lean {
+struct iterator_on_term_with_basis_var:linear_combination_iterator<mpq> {
+    std::unordered_map<unsigned, mpq>::const_iterator m_i; // the offset in term coeffs
+    bool m_term_j_returned = false;
+    const lar_term & m_term;
+    unsigned m_term_j;
+    unsigned size() const {return static_cast<unsigned>(m_term.m_coeffs.size() + 1);}
+    iterator_on_term_with_basis_var(const lar_term & t, unsigned term_j) :
+        m_i(t.m_coeffs.begin()),
+        m_term(t),
+        m_term_j(term_j) {}
+
+    bool next(mpq & a, unsigned & i) {
+        if (m_term_j_returned == false) {
+            m_term_j_returned = true;
+            a = - one_of_type<mpq>();
+            i = m_term_j;
+            return true;
+        }
+        if (m_i == m_term.m_coeffs.end())
+            return false;
+        i = m_i->first;
+        a = m_i->second;
+        m_i++;
+        return true;
+    }
+    bool next(unsigned & i) {
+        if (m_term_j_returned == false) {
+            m_term_j_returned = true;
+            i = m_term_j;
+            return true;
+        }
+        if (m_i == m_term.m_coeffs.end())
+            return false;
+        i = m_i->first;
+        m_i++;
+        return true;
+    }
+    void reset() {
+        m_term_j_returned = false;
+        m_i = m_term.m_coeffs.begin();
+    }
+    linear_combination_iterator<mpq> * clone() {
+        iterator_on_term_with_basis_var * r = new iterator_on_term_with_basis_var(m_term, m_term_j);
+        return r;
+    }
+};
+}

src/util/lp/lar_constraints.h

@@ -0,0 +1,86 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include <utility>
+#include <unordered_map>
+#include <string>
+#include <algorithm>
+#include "util/lp/lp_utils.h"
+#include "util/lp/ul_pair.h"
+#include "util/lp/lar_term.h"
+namespace lean {
+inline lconstraint_kind flip_kind(lconstraint_kind t) {
+    return static_cast<lconstraint_kind>( - static_cast<int>(t));
+}
+
+inline std::string lconstraint_kind_string(lconstraint_kind t) {
+    switch (t) {
+    case LE: return std::string("<=");
+    case LT: return std::string("<");
+    case GE: return std::string(">=");
+    case GT: return std::string(">");
+    case EQ: return std::string("=");
+    }
+    lean_unreachable();
+    return std::string(); // it is unreachable
+}
+
+class lar_base_constraint {
+public:
+    lconstraint_kind m_kind;
+    mpq m_right_side;
+    virtual vector<std::pair<mpq, var_index>> get_left_side_coefficients() const = 0;
+    lar_base_constraint() {}
+    lar_base_constraint(lconstraint_kind kind, const mpq& right_side) :m_kind(kind), m_right_side(right_side) {}
+
+    virtual unsigned size() const = 0;
+    virtual ~lar_base_constraint(){}
+    virtual mpq get_free_coeff_of_left_side() const { return zero_of_type<mpq>();}
+};
+
+struct lar_var_constraint: public lar_base_constraint {
+    unsigned m_j;
+    vector<std::pair<mpq, var_index>> get_left_side_coefficients() const {
+        vector<std::pair<mpq, var_index>> ret;
+        ret.push_back(std::make_pair(one_of_type<mpq>(), m_j));
+        return ret;
+    }
+    unsigned size() const { return 1;}
+    lar_var_constraint(unsigned j, lconstraint_kind kind, const mpq& right_side) : lar_base_constraint(kind, right_side), m_j(j) { }
+};
+
+
+struct lar_term_constraint: public lar_base_constraint {
+    const lar_term * m_term;
+    vector<std::pair<mpq, var_index>> get_left_side_coefficients() const {
+        return m_term->coeffs_as_vector();
+    }
+    unsigned size() const { return m_term->size();}
+    lar_term_constraint(const lar_term *t, lconstraint_kind kind, const mpq& right_side) : lar_base_constraint(kind, right_side), m_term(t) { }
+    virtual mpq get_free_coeff_of_left_side() const { return m_term->m_v;}
+
+};
+
+
+class lar_constraint : public lar_base_constraint {
+public:
+    vector<std::pair<mpq, var_index>> m_coeffs;
+    lar_constraint() {} 
+    lar_constraint(const vector<std::pair<mpq, var_index>> & left_side, lconstraint_kind kind, const mpq & right_side)
+        :  lar_base_constraint(kind, right_side), m_coeffs(left_side) {}
+    
+    lar_constraint(const lar_base_constraint & c) {
+        lean_assert(false); // should not be called : todo!
+    }
+
+    unsigned size() const {
+        return static_cast<unsigned>(m_coeffs.size());
+    }
+
+    vector<std::pair<mpq, var_index>> get_left_side_coefficients() const { return m_coeffs; }
+};
+}

src/util/lp/lar_core_solver.h

@@ -0,0 +1,802 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/vector.h"
+#include <string>
+#include <utility>
+#include "util/lp/lp_core_solver_base.h"
+#include <algorithm>
+#include "util/lp/indexed_vector.h"
+#include "util/lp/binary_heap_priority_queue.h"
+#include "util/lp/breakpoint.h"
+#include "util/lp/stacked_unordered_set.h"
+#include "util/lp/lp_primal_core_solver.h"
+#include "util/lp/stacked_vector.h"
+#include "util/lp/lar_solution_signature.h"
+#include "util/lp/iterator_on_column.h"
+#include "util/lp/iterator_on_indexed_vector.h"
+#include "util/lp/stacked_value.h"
+namespace lean {
+
+class lar_core_solver  {
+    // m_sign_of_entering is set to 1 if the entering variable needs
+    // to grow and is set to -1  otherwise
+    int m_sign_of_entering_delta;
+    vector<std::pair<mpq, unsigned>> m_infeasible_linear_combination;
+    int m_infeasible_sum_sign = 0; // todo: get rid of this field
+    vector<numeric_pair<mpq>> m_right_sides_dummy;
+    vector<mpq> m_costs_dummy;
+    vector<double> m_d_right_sides_dummy;
+    vector<double> m_d_costs_dummy;
+public:
+    stacked_value<simplex_strategy_enum> m_stacked_simplex_strategy;
+    stacked_vector<column_type> m_column_types;
+    // r - solver fields, for rational numbers
+    vector<numeric_pair<mpq>> m_r_x; // the solution
+    stacked_vector<numeric_pair<mpq>> m_r_low_bounds;
+    stacked_vector<numeric_pair<mpq>> m_r_upper_bounds;
+    static_matrix<mpq, numeric_pair<mpq>> m_r_A;
+    stacked_vector<unsigned> m_r_pushed_basis;
+    vector<unsigned> m_r_basis;
+    vector<unsigned> m_r_nbasis;
+    vector<int> m_r_heading;
+    stacked_vector<unsigned> m_r_columns_nz;
+    stacked_vector<unsigned> m_r_rows_nz;
+    
+    // d - solver fields, for doubles
+    vector<double> m_d_x; // the solution in doubles
+    vector<double> m_d_low_bounds;
+    vector<double> m_d_upper_bounds;
+    static_matrix<double, double> m_d_A;
+    stacked_vector<unsigned> m_d_pushed_basis;
+    vector<unsigned> m_d_basis;
+    vector<unsigned> m_d_nbasis;
+    vector<int> m_d_heading;
+
+
+    lp_primal_core_solver<mpq, numeric_pair<mpq>> m_r_solver; // solver in rational numbers
+
+    lp_primal_core_solver<double, double> m_d_solver; // solver in doubles
+    
+    lar_core_solver(
+                    lp_settings & settings,
+                    const column_namer & column_names
+                    );
+
+    lp_settings & settings() { return m_r_solver.m_settings;}
+    const lp_settings & settings() const { return m_r_solver.m_settings;}
+    
+    int get_infeasible_sum_sign() const { return m_infeasible_sum_sign;   }
+
+    const vector<std::pair<mpq, unsigned>> & get_infeasibility_info(int & inf_sign) const {
+        inf_sign = m_infeasible_sum_sign;
+        return m_infeasible_linear_combination;
+    }
+
+    void fill_not_improvable_zero_sum_from_inf_row();
+    
+    column_type get_column_type(unsigned j) { return m_column_types[j];}
+    
+    void init_costs(bool first_time);
+
+    void init_cost_for_column(unsigned j);
+
+    // returns m_sign_of_alpha_r
+    int column_is_out_of_bounds(unsigned j);
+
+    void calculate_pivot_row(unsigned i);
+
+    void print_pivot_row(std::ostream & out, unsigned row_index) const  { // remove later debug !!!!
+        for (unsigned j : m_r_solver.m_pivot_row.m_index) {
+            if (numeric_traits<mpq>::is_pos(m_r_solver.m_pivot_row.m_data[j]))
+                out << "+";
+            out << m_r_solver.m_pivot_row.m_data[j] << m_r_solver.column_name(j) << " ";
+        }
+        
+        out << " +" << m_r_solver.column_name(m_r_solver.m_basis[row_index]) << std::endl;
+        
+        for (unsigned j : m_r_solver.m_pivot_row.m_index) {
+            m_r_solver.print_column_bound_info(j, out);
+        }
+        m_r_solver.print_column_bound_info(m_r_solver.m_basis[row_index], out);
+        
+    }
+    
+
+    void advance_on_sorted_breakpoints(unsigned entering);
+
+    void change_slope_on_breakpoint(unsigned entering, breakpoint<numeric_pair<mpq>> * b, mpq & slope_at_entering);
+
+    bool row_is_infeasible(unsigned row);
+
+    bool row_is_evidence(unsigned row);
+
+    bool find_evidence_row();
+
+    void prefix_r();
+
+    void prefix_d();
+
+    unsigned m_m() const {
+        return m_r_A.row_count();
+    }
+
+    unsigned m_n() const {
+        return m_r_A.column_count();
+    }
+    
+    bool is_tiny() const { return this->m_m() < 10 && this->m_n() < 20; }
+
+    bool is_empty() const { return this->m_m() == 0 && this->m_n() == 0; }
+
+    template <typename L>
+    int get_sign(const L & v) {
+        return v > zero_of_type<L>() ? 1 : (v < zero_of_type<L>() ? -1 : 0);
+    }
+
+
+
+    void fill_evidence(unsigned row);
+
+
+
+    void solve();
+
+    bool low_bounds_are_set() const { return true; }
+
+    const indexed_vector<mpq> & get_pivot_row() const {
+        return m_r_solver.m_pivot_row;
+    }
+    
+    void fill_not_improvable_zero_sum();
+
+    void pop_basis(unsigned k) {
+        if (!settings().use_tableau()) {
+            m_r_pushed_basis.pop(k);        
+            m_r_basis = m_r_pushed_basis();
+            m_r_solver.init_basis_heading_and_non_basic_columns_vector();
+            m_d_pushed_basis.pop(k);
+            m_d_basis = m_d_pushed_basis();
+            m_d_solver.init_basis_heading_and_non_basic_columns_vector();
+        } else {
+            m_d_basis = m_r_basis;
+            m_d_nbasis = m_r_nbasis;
+            m_d_heading = m_r_heading;
+        }
+    }
+
+    void push() {
+        lean_assert(m_r_solver.basis_heading_is_correct());
+        lean_assert(!need_to_presolve_with_double_solver() || m_d_solver.basis_heading_is_correct());
+        lean_assert(m_column_types.size() == m_r_A.column_count());
+        m_stacked_simplex_strategy = settings().simplex_strategy();
+        m_stacked_simplex_strategy.push();
+        m_column_types.push();
+        // rational
+        if (!settings().use_tableau()) 
+            m_r_A.push();
+        m_r_low_bounds.push();
+        m_r_upper_bounds.push();
+        if (!settings().use_tableau()) {
+            push_vector(m_r_pushed_basis, m_r_basis);
+            push_vector(m_r_columns_nz, m_r_solver.m_columns_nz);
+            push_vector(m_r_rows_nz, m_r_solver.m_rows_nz);
+        }
+        
+        m_d_A.push();
+        if (!settings().use_tableau())
+            push_vector(m_d_pushed_basis, m_d_basis);
+    }
+
+    template <typename K> 
+    void push_vector(stacked_vector<K> & pushed_vector, const vector<K> & vector) {
+        lean_assert(pushed_vector.size() <= vector.size());
+        for (unsigned i = 0; i < vector.size();i++) {
+            if (i == pushed_vector.size()) {
+                pushed_vector.push_back(vector[i]);
+            } else {
+                pushed_vector[i] = vector[i];
+            }
+        }
+        pushed_vector.push();
+    }
+
+    void pop_markowitz_counts(unsigned k) {
+        m_r_columns_nz.pop(k);
+        m_r_rows_nz.pop(k);
+        m_r_solver.m_columns_nz.resize(m_r_columns_nz.size());
+        m_r_solver.m_rows_nz.resize(m_r_rows_nz.size());
+        for (unsigned i = 0; i < m_r_columns_nz.size(); i++)
+            m_r_solver.m_columns_nz[i] = m_r_columns_nz[i];
+        for (unsigned i = 0; i < m_r_rows_nz.size(); i++)
+            m_r_solver.m_rows_nz[i] = m_r_rows_nz[i];
+    }
+
+    
+    void pop(unsigned k) {
+        m_stacked_simplex_strategy.pop(k);
+        bool use_tableau = m_stacked_simplex_strategy() != simplex_strategy_enum::no_tableau;
+        // rationals
+        if (!settings().use_tableau()) 
+            m_r_A.pop(k);
+        m_r_low_bounds.pop(k);
+        m_r_upper_bounds.pop(k);
+        m_column_types.pop(k);
+        
+        if (m_r_solver.m_factorization != nullptr) {
+            delete m_r_solver.m_factorization;
+            m_r_solver.m_factorization = nullptr;
+        }
+        m_r_x.resize(m_r_A.column_count());
+        m_r_solver.m_costs.resize(m_r_A.column_count());
+        m_r_solver.m_d.resize(m_r_A.column_count());
+        if(!use_tableau)
+            pop_markowitz_counts(k);
+        m_d_A.pop(k);
+        if (m_d_solver.m_factorization != nullptr) {
+            delete m_d_solver.m_factorization;
+            m_d_solver.m_factorization = nullptr;
+        }
+        
+        m_d_x.resize(m_d_A.column_count());
+        pop_basis(k);
+
+        lean_assert(m_r_solver.basis_heading_is_correct());
+        lean_assert(!need_to_presolve_with_double_solver() || m_d_solver.basis_heading_is_correct());
+    }
+
+    bool need_to_presolve_with_double_solver() const {
+        return settings().presolve_with_double_solver_for_lar && !settings().use_tableau();
+    }
+
+    template <typename L>
+    bool is_zero_vector(const vector<L> & b) {
+        for (const L & m: b)
+            if (!is_zero(m)) return false;
+        return true;
+    }
+
+
+    bool update_xj_and_get_delta(unsigned j, non_basic_column_value_position pos_type, numeric_pair<mpq> & delta) {
+        auto & x = m_r_x[j];
+        switch (pos_type) {
+        case at_low_bound:
+            if (x == m_r_solver.m_low_bounds[j])
+                return false;
+            delta = m_r_solver.m_low_bounds[j] - x;
+            m_r_solver.m_x[j] = m_r_solver.m_low_bounds[j];
+            break;
+        case at_fixed:
+        case at_upper_bound:
+            if (x == m_r_solver.m_upper_bounds[j])
+                return false;
+            delta = m_r_solver.m_upper_bounds[j] - x;
+            x = m_r_solver.m_upper_bounds[j];
+            break;
+        case free_of_bounds: {
+            return false;
+        }
+        case not_at_bound:
+            switch (m_column_types[j]) {
+            case column_type::free_column:
+                return false;
+            case column_type::upper_bound:
+                delta = m_r_solver.m_upper_bounds[j] - x;
+                x = m_r_solver.m_upper_bounds[j];
+                break;
+            case column_type::low_bound:
+                delta = m_r_solver.m_low_bounds[j] - x;
+                x = m_r_solver.m_low_bounds[j];
+                break;
+            case column_type::boxed:
+                if (x > m_r_solver.m_upper_bounds[j]) {
+                    delta = m_r_solver.m_upper_bounds[j] - x;
+                    x += m_r_solver.m_upper_bounds[j];
+                } else {
+                    delta = m_r_solver.m_low_bounds[j] - x;
+                    x = m_r_solver.m_low_bounds[j];
+                }
+                break;
+            case column_type::fixed:
+                delta = m_r_solver.m_low_bounds[j] - x;
+                x = m_r_solver.m_low_bounds[j];
+                break;
+
+            default:
+                lean_assert(false);
+            }
+            break;
+        default:
+            lean_unreachable();
+        }
+        m_r_solver.remove_column_from_inf_set(j);
+        return true;
+    }
+
+    
+    
+    void prepare_solver_x_with_signature_tableau(const lar_solution_signature & signature) {
+        lean_assert(m_r_solver.inf_set_is_correct());
+        for (auto &t : signature) {
+            unsigned j = t.first;
+            if (m_r_heading[j] >= 0)
+                continue;
+            auto pos_type = t.second;
+            numeric_pair<mpq> delta;
+            if (!update_xj_and_get_delta(j, pos_type, delta))
+                continue;
+            for (const auto & cc : m_r_solver.m_A.m_columns[j]){
+                unsigned i = cc.m_i;
+                unsigned jb = m_r_solver.m_basis[i];
+                m_r_solver.m_x[jb] -= delta * m_r_solver.m_A.get_val(cc);
+                m_r_solver.update_column_in_inf_set(jb);
+            }
+            lean_assert(m_r_solver.A_mult_x_is_off() == false);
+        }
+        lean_assert(m_r_solver.inf_set_is_correct());
+    }
+
+    
+    template <typename L, typename K>
+    void prepare_solver_x_with_signature(const lar_solution_signature & signature, lp_primal_core_solver<L,K> & s) {
+        for (auto &t : signature) {
+            unsigned j = t.first;
+            lean_assert(m_r_heading[j] < 0);
+            auto pos_type = t.second;
+            switch (pos_type) {
+            case at_low_bound:
+                s.m_x[j] = s.m_low_bounds[j];
+                break;
+            case at_fixed:
+            case at_upper_bound:
+                s.m_x[j] = s.m_upper_bounds[j];
+                break;
+            case free_of_bounds: {
+                s.m_x[j] = zero_of_type<K>();
+                continue;
+            }
+            case not_at_bound:
+                  switch (m_column_types[j]) {
+                  case column_type::free_column:
+                      lean_assert(false); // unreachable
+                  case column_type::upper_bound:
+                      s.m_x[j] = s.m_upper_bounds[j];
+                      break;
+                  case column_type::low_bound:
+                      s.m_x[j] = s.m_low_bounds[j];
+                      break;
+                  case column_type::boxed:
+                      if (my_random() % 2) {
+                          s.m_x[j] = s.m_low_bounds[j];
+                      } else {
+                          s.m_x[j] = s.m_upper_bounds[j];
+                      }
+                      break;
+                  case column_type::fixed:
+                      s.m_x[j] = s.m_low_bounds[j];
+                      break;
+                  default:
+                      lean_assert(false);
+                  }
+                  break;
+            default:
+                lean_unreachable();
+            }
+        }
+
+        lean_assert(is_zero_vector(s.m_b));
+        s.solve_Ax_eq_b();
+    }
+
+    template <typename L, typename K> 
+    void catch_up_in_lu_in_reverse(const vector<unsigned> & trace_of_basis_change, lp_primal_core_solver<L,K> & cs) {
+        // recover the previous working basis
+        for (unsigned i = trace_of_basis_change.size(); i > 0;  i-= 2) {
+            unsigned entering = trace_of_basis_change[i-1];
+            unsigned leaving = trace_of_basis_change[i-2];
+            cs.change_basis_unconditionally(entering, leaving);
+        }
+        cs.init_lu();
+    }
+
+    //basis_heading is the basis heading of the solver owning trace_of_basis_change
+    // here we compact the trace as we go to avoid unnecessary column changes
+    template <typename L, typename K> 
+    void catch_up_in_lu(const vector<unsigned> & trace_of_basis_change, const vector<int> & basis_heading, lp_primal_core_solver<L,K> & cs) {
+        if (cs.m_factorization == nullptr || cs.m_factorization->m_refactor_counter + trace_of_basis_change.size()/2 >= 200) {
+            for (unsigned i = 0; i < trace_of_basis_change.size(); i+= 2) {
+                unsigned entering = trace_of_basis_change[i];
+                unsigned leaving = trace_of_basis_change[i+1];
+                cs.change_basis_unconditionally(entering, leaving);
+            }
+            if (cs.m_factorization != nullptr)
+                delete cs.m_factorization;
+            cs.m_factorization = nullptr;
+        } else {
+            indexed_vector<L> w(cs.m_A.row_count());
+            // the queues of delayed indices
+            std::queue<unsigned> entr_q, leav_q;
+            auto * l = cs.m_factorization;
+            lean_assert(l->get_status() == LU_status::OK);
+            for (unsigned i = 0; i < trace_of_basis_change.size(); i+= 2) {
+                unsigned entering = trace_of_basis_change[i];
+                unsigned leaving = trace_of_basis_change[i+1];
+                bool good_e = basis_heading[entering] >= 0 && cs.m_basis_heading[entering] < 0;
+                bool good_l = basis_heading[leaving] < 0 && cs.m_basis_heading[leaving] >= 0;
+                if (!good_e && !good_l) continue;
+                if (good_e && !good_l) {
+                    while (!leav_q.empty() && cs.m_basis_heading[leav_q.front()] < 0)
+                        leav_q.pop();
+                    if (!leav_q.empty()) {
+                        leaving = leav_q.front();
+                        leav_q.pop();
+                    } else {
+                        entr_q.push(entering);
+                        continue;
+                    }
+                } else if (!good_e && good_l) {
+                    while (!entr_q.empty() && cs.m_basis_heading[entr_q.front()] >= 0)
+                        entr_q.pop();
+                    if (!entr_q.empty()) {
+                        entering = entr_q.front();
+                        entr_q.pop();
+                    } else {
+                        leav_q.push(leaving);
+                        continue;
+                    }
+                }
+                lean_assert(cs.m_basis_heading[entering] < 0);
+                lean_assert(cs.m_basis_heading[leaving] >= 0);
+                if (l->get_status() == LU_status::OK) {
+                    l->prepare_entering(entering, w); // to init vector w
+                    l->replace_column(zero_of_type<L>(), w, cs.m_basis_heading[leaving]);
+                }
+                cs.change_basis_unconditionally(entering, leaving);
+            }
+            if (l->get_status() != LU_status::OK) {
+                delete l;
+                cs.m_factorization = nullptr;
+            }
+        }
+        if (cs.m_factorization == nullptr) {
+            if (numeric_traits<L>::precise())
+                init_factorization(cs.m_factorization, cs.m_A, cs.m_basis, settings());
+        }
+    }
+
+    bool no_r_lu() const {
+        return m_r_solver.m_factorization == nullptr || m_r_solver.m_factorization->get_status() == LU_status::Degenerated; 
+    }
+
+    void solve_on_signature_tableau(const lar_solution_signature & signature, const vector<unsigned> & changes_of_basis) {
+        r_basis_is_OK();
+        lean_assert(settings().use_tableau());
+        bool r = catch_up_in_lu_tableau(changes_of_basis, m_d_solver.m_basis_heading);
+
+        if (!r) { // it is the case where m_d_solver gives a degenerated basis
+            prepare_solver_x_with_signature_tableau(signature); // still are going to use the signature partially
+            m_r_solver.find_feasible_solution();
+            m_d_basis = m_r_basis;
+            m_d_heading = m_r_heading;
+            m_d_nbasis = m_r_nbasis;
+            delete m_d_solver.m_factorization;
+            m_d_solver.m_factorization = nullptr;
+        } else {
+            prepare_solver_x_with_signature_tableau(signature);
+            m_r_solver.start_tracing_basis_changes();
+            m_r_solver.find_feasible_solution();
+            if (settings().get_cancel_flag())
+                return;
+            m_r_solver.stop_tracing_basis_changes();
+            // and now catch up in the double solver
+            lean_assert(m_r_solver.total_iterations() >= m_r_solver.m_trace_of_basis_change_vector.size() /2);
+            catch_up_in_lu(m_r_solver.m_trace_of_basis_change_vector, m_r_solver.m_basis_heading, m_d_solver);
+        }
+        lean_assert(r_basis_is_OK());
+    }
+
+    bool adjust_x_of_column(unsigned j) {
+        /*
+        if (m_r_solver.m_basis_heading[j] >= 0) {
+            return false;
+        }
+
+        if (m_r_solver.column_is_feasible(j)) {
+            return false;
+        }
+
+        m_r_solver.snap_column_to_bound_tableau(j);
+        lean_assert(m_r_solver.column_is_feasible(j));
+        m_r_solver.m_inf_set.erase(j);
+        */
+        lean_assert(false);
+        return true;
+    }
+
+    
+    bool catch_up_in_lu_tableau(const vector<unsigned> & trace_of_basis_change, const vector<int> & basis_heading) {
+        lean_assert(r_basis_is_OK());
+        // the queues of delayed indices
+        std::queue<unsigned> entr_q, leav_q;
+        for (unsigned i = 0; i < trace_of_basis_change.size(); i+= 2) {
+            unsigned entering = trace_of_basis_change[i];
+            unsigned leaving = trace_of_basis_change[i+1];
+            bool good_e = basis_heading[entering] >= 0 && m_r_solver.m_basis_heading[entering] < 0;
+            bool good_l = basis_heading[leaving] < 0 && m_r_solver.m_basis_heading[leaving] >= 0;
+            if (!good_e && !good_l) continue;
+            if (good_e && !good_l) {
+                while (!leav_q.empty() && m_r_solver.m_basis_heading[leav_q.front()] < 0)
+                    leav_q.pop();
+                if (!leav_q.empty()) {
+                    leaving = leav_q.front();
+                    leav_q.pop();
+                } else {
+                    entr_q.push(entering);
+                    continue;
+                }
+            } else if (!good_e && good_l) {
+                while (!entr_q.empty() && m_r_solver.m_basis_heading[entr_q.front()] >= 0)
+                    entr_q.pop();
+                if (!entr_q.empty()) {
+                    entering = entr_q.front();
+                    entr_q.pop();
+                } else {
+                    leav_q.push(leaving);
+                    continue;
+                }
+            }
+            lean_assert(m_r_solver.m_basis_heading[entering] < 0);
+            lean_assert(m_r_solver.m_basis_heading[leaving] >= 0);
+            m_r_solver.change_basis_unconditionally(entering, leaving);
+            if(!m_r_solver.pivot_column_tableau(entering, m_r_solver.m_basis_heading[entering])) {
+				// unroll the last step
+                m_r_solver.change_basis_unconditionally(leaving, entering);
+#ifdef LEAN_DEBUG
+                bool t =
+#endif
+                    m_r_solver.pivot_column_tableau(leaving, m_r_solver.m_basis_heading[leaving]);
+#ifdef LEAN_DEBUG
+                lean_assert(t);
+#endif 
+                return false;
+            }
+        }
+        lean_assert(r_basis_is_OK());
+        return true;
+    }
+
+
+    bool r_basis_is_OK() const {
+#ifdef LEAN_DEBUG
+        if (!m_r_solver.m_settings.use_tableau())
+            return true;
+        for (unsigned j : m_r_solver.m_basis) {
+            lean_assert(m_r_solver.m_A.m_columns[j].size() == 1);
+            lean_assert(m_r_solver.m_A.get_val(m_r_solver.m_A.m_columns[j][0]) == one_of_type<mpq>());
+        }
+        for (unsigned j =0; j < m_r_solver.m_basis_heading.size(); j++) {
+            if (m_r_solver.m_basis_heading[j] >= 0) continue;
+            if (m_r_solver.m_column_types[j] == column_type::fixed) continue;
+            lean_assert(static_cast<unsigned>(- m_r_solver.m_basis_heading[j] - 1) < m_r_solver.m_column_types.size());
+            lean_assert( m_r_solver.m_basis_heading[j] <= -1);
+        }
+#endif
+        return true;
+    }
+    
+    void solve_on_signature(const lar_solution_signature & signature, const vector<unsigned> & changes_of_basis) {
+        lean_assert(!settings().use_tableau());
+        if (m_r_solver.m_factorization == nullptr) {
+            for (unsigned j = 0; j < changes_of_basis.size(); j+=2) {
+                unsigned entering = changes_of_basis[j];
+                unsigned leaving = changes_of_basis[j + 1];
+                m_r_solver.change_basis_unconditionally(entering, leaving);
+            }
+            init_factorization(m_r_solver.m_factorization, m_r_A, m_r_basis, settings());
+        } else {
+            catch_up_in_lu(changes_of_basis, m_d_solver.m_basis_heading, m_r_solver);
+        }
+
+        if (no_r_lu()) { // it is the case where m_d_solver gives a degenerated basis, we need to roll back
+            std::cout << "no_r_lu" << std::endl;
+            catch_up_in_lu_in_reverse(changes_of_basis, m_r_solver);
+            m_r_solver.find_feasible_solution();
+            m_d_basis = m_r_basis;
+            m_d_heading = m_r_heading;
+            m_d_nbasis = m_r_nbasis;
+            delete m_d_solver.m_factorization;
+            m_d_solver.m_factorization = nullptr;
+        } else {
+            prepare_solver_x_with_signature(signature, m_r_solver);
+            m_r_solver.start_tracing_basis_changes();
+            m_r_solver.find_feasible_solution();
+            if (settings().get_cancel_flag())
+                return;
+            m_r_solver.stop_tracing_basis_changes();
+            // and now catch up in the double solver
+            lean_assert(m_r_solver.total_iterations() >= m_r_solver.m_trace_of_basis_change_vector.size() /2);
+            catch_up_in_lu(m_r_solver.m_trace_of_basis_change_vector, m_r_solver.m_basis_heading, m_d_solver);
+        }
+    }
+
+    void create_double_matrix(static_matrix<double, double> & A) {
+        for (unsigned i = 0; i < m_r_A.row_count(); i++) {
+            auto & row = m_r_A.m_rows[i];
+            for (row_cell<mpq> & c : row) {
+                A.set(i, c.m_j, c.get_val().get_double());
+            }
+        }
+    }
+
+    void fill_basis_d(
+                      vector<unsigned>& basis_d,
+                      vector<int>& heading_d,
+                      vector<unsigned>& nbasis_d){
+        basis_d = m_r_basis;
+        heading_d = m_r_heading;
+        nbasis_d = m_r_nbasis;
+    }
+
+    template <typename L, typename K>
+    void extract_signature_from_lp_core_solver(const lp_primal_core_solver<L, K> & solver, lar_solution_signature & signature) {
+        signature.clear();
+        lean_assert(signature.size() == 0);
+        for (unsigned j = 0; j < solver.m_basis_heading.size(); j++) {
+            if (solver.m_basis_heading[j] < 0) {
+                signature[j] = solver.get_non_basic_column_value_position(j);
+            }
+        }
+    }
+
+    void get_bounds_for_double_solver() {
+        unsigned n = m_n();
+        m_d_low_bounds.resize(n);
+        m_d_upper_bounds.resize(n);
+        double delta = find_delta_for_strict_boxed_bounds().get_double();
+        if (delta > 0.000001)
+            delta = 0.000001;
+        for (unsigned j = 0; j < n; j++) {
+            if (low_bound_is_set(j)) {
+                const auto & lb = m_r_solver.m_low_bounds[j];
+                m_d_low_bounds[j] = lb.x.get_double() + delta * lb.y.get_double();
+            }
+            if (upper_bound_is_set(j)) {
+                const auto & ub = m_r_solver.m_upper_bounds[j];
+                m_d_upper_bounds[j] = ub.x.get_double() + delta * ub.y.get_double();
+                lean_assert(!low_bound_is_set(j) || (m_d_upper_bounds[j] >= m_d_low_bounds[j]));
+            }
+        }
+    }
+
+    void scale_problem_for_doubles(
+                        static_matrix<double, double>& A,        
+                        vector<double> & low_bounds,
+                        vector<double> & upper_bounds) {
+        vector<double> column_scale_vector;
+        vector<double> right_side_vector(A.column_count());
+        settings().reps_in_scaler = 5;
+        scaler<double, double > scaler(right_side_vector,
+                                       A,
+                                       settings().scaling_minimum,
+                                       settings().scaling_maximum,
+                                       column_scale_vector,
+                                       settings());
+        if (! scaler.scale()) {
+            // the scale did not succeed, unscaling
+            A.clear();
+            create_double_matrix(A);
+        } else {
+            for (unsigned j = 0; j < A.column_count(); j++) {
+                if (m_r_solver.column_has_upper_bound(j)) {
+                    upper_bounds[j] /= column_scale_vector[j];
+                }
+                if (m_r_solver.column_has_low_bound(j)) {
+                    low_bounds[j] /= column_scale_vector[j];
+                }
+            }
+        }
+        
+    }
+    // returns the trace of basis changes
+    vector<unsigned> find_solution_signature_with_doubles(lar_solution_signature & signature) {
+        if (m_d_solver.m_factorization == nullptr || m_d_solver.m_factorization->get_status() != LU_status::OK) {
+            vector<unsigned> ret;
+            return ret;
+        }
+        get_bounds_for_double_solver();
+
+        extract_signature_from_lp_core_solver(m_r_solver, signature);
+        prepare_solver_x_with_signature(signature, m_d_solver);
+        m_d_solver.start_tracing_basis_changes();
+        m_d_solver.find_feasible_solution();
+        if (settings().get_cancel_flag())
+            return vector<unsigned>();
+            
+        m_d_solver.stop_tracing_basis_changes();
+        extract_signature_from_lp_core_solver(m_d_solver, signature);
+        return m_d_solver.m_trace_of_basis_change_vector;
+    }
+
+
+    bool low_bound_is_set(unsigned j) const {
+        switch (m_column_types[j]) {
+        case column_type::free_column:
+        case column_type::upper_bound:
+            return false;
+        case column_type::low_bound:
+        case column_type::boxed:
+        case column_type::fixed:
+            return true;
+        default:
+            lean_assert(false);
+        }
+        return false;
+    }
+    
+    bool upper_bound_is_set(unsigned j) const {
+        switch (m_column_types[j]) {
+        case column_type::free_column:
+        case column_type::low_bound:
+            return false;
+        case column_type::upper_bound:
+        case column_type::boxed:
+        case column_type::fixed:
+            return true;
+        default:
+            lean_assert(false);
+        }
+        return false;
+    }
+
+    void update_delta(mpq& delta, numeric_pair<mpq> const& l, numeric_pair<mpq> const& u) const {
+        lean_assert(l <= u);
+        if (l.x < u.x && l.y > u.y) {
+            mpq delta1 = (u.x - l.x) / (l.y - u.y);
+            if (delta1 < delta) {
+                delta = delta1;
+            }
+        }
+        lean_assert(l.x + delta * l.y <= u.x + delta * u.y);
+    }
+
+
+    mpq find_delta_for_strict_boxed_bounds() const{
+        mpq delta = numeric_traits<mpq>::one();
+        for (unsigned j = 0; j < m_r_A.column_count(); j++ ) {
+            if (m_column_types()[j] != column_type::boxed)
+                continue;
+            update_delta(delta, m_r_low_bounds[j], m_r_upper_bounds[j]);
+
+        }
+        return delta;
+    }
+
+    
+    mpq find_delta_for_strict_bounds() const{
+        mpq delta = numeric_traits<mpq>::one();
+        for (unsigned j = 0; j < m_r_A.column_count(); j++ ) {
+            if (low_bound_is_set(j))
+                update_delta(delta, m_r_low_bounds[j], m_r_x[j]);
+            if (upper_bound_is_set(j))
+                update_delta(delta, m_r_x[j], m_r_upper_bounds[j]);
+        }
+        return delta;
+    }
+
+    void init_column_row_nz_for_r_solver() {
+        m_r_solver.init_column_row_non_zeroes();
+    }
+
+    linear_combination_iterator<mpq> * get_column_iterator(unsigned j) {
+        if (settings().use_tableau()) {
+            return new iterator_on_column<mpq, numeric_pair<mpq>>(m_r_solver.m_A.m_columns[j], m_r_solver.m_A);
+        } else {
+            m_r_solver.solve_Bd(j);
+            return new iterator_on_indexed_vector<mpq>(m_r_solver.m_ed);
+        }
+    }
+    
+};
+}

src/util/lp/lar_core_solver.hpp

@@ -0,0 +1,292 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <string>
+#include "util/vector.h"
+#include "util/lp/lar_core_solver.h"
+#include "util/lp/lar_solution_signature.h"
+namespace lean {
+lar_core_solver::lar_core_solver(
+                                 lp_settings & settings,
+                                 const column_namer & column_names
+):
+    m_r_solver(m_r_A,
+                    m_right_sides_dummy,
+                    m_r_x,
+                    m_r_basis,
+                    m_r_nbasis,
+                    m_r_heading,
+                    m_costs_dummy,
+                    m_column_types(),
+                    m_r_low_bounds(),
+                    m_r_upper_bounds(),
+                    settings,
+               column_names),
+    m_d_solver(m_d_A,
+                    m_d_right_sides_dummy,
+                    m_d_x,
+                    m_d_basis,
+                    m_d_nbasis,
+                    m_d_heading,
+                    m_d_costs_dummy,
+                    m_column_types(),
+                    m_d_low_bounds,
+                    m_d_upper_bounds,
+                    settings,
+                    column_names){}
+
+void lar_core_solver::init_costs(bool first_time) {
+    lean_assert(false); // should not be called
+    // lean_assert(this->m_x.size() >= this->m_n());
+    // lean_assert(this->m_column_types.size() >= this->m_n());
+    // if (first_time)
+    //     this->m_costs.resize(this->m_n());
+    // X inf = this->m_infeasibility;
+    // this->m_infeasibility = zero_of_type<X>();
+    // for (unsigned j = this->m_n(); j--;)
+    //     init_cost_for_column(j);
+    // if (!(first_time || inf >= this->m_infeasibility)) {
+    //     LP_OUT(this->m_settings, "iter = " << this->total_iterations() << std::endl);
+    //     LP_OUT(this->m_settings, "inf was " << T_to_string(inf) << " and now " << T_to_string(this->m_infeasibility) << std::endl);
+    //     lean_assert(false);
+    // }
+    // if (inf == this->m_infeasibility)
+    //     this->m_iters_with_no_cost_growing++;
+}
+
+
+void lar_core_solver::init_cost_for_column(unsigned j) {
+    /*
+    // If j is a breakpoint column, then we set the cost zero.
+    // When anylyzing an entering column candidate we update the cost of the breakpoints columns to get the left or the right derivative if the infeasibility function
+    const numeric_pair<mpq> & x = this->m_x[j];
+    // set zero cost for each non-basis column
+    if (this->m_basis_heading[j] < 0) {
+        this->m_costs[j] = numeric_traits<T>::zero();
+        return;
+    }
+    // j is a basis column
+    switch (this->m_column_types[j]) {
+    case fixed:
+    case column_type::boxed:
+        if (x > this->m_upper_bounds[j]) {
+            this->m_costs[j] = 1;
+            this->m_infeasibility += x - this->m_upper_bounds[j];
+        } else if (x < this->m_low_bounds[j]) {
+            this->m_infeasibility += this->m_low_bounds[j] - x;
+            this->m_costs[j] = -1;
+        } else {
+            this->m_costs[j] = numeric_traits<T>::zero();
+        }
+        break;
+    case low_bound:
+        if (x < this->m_low_bounds[j]) {
+            this->m_costs[j] = -1;
+            this->m_infeasibility += this->m_low_bounds[j] - x;
+        } else {
+            this->m_costs[j] = numeric_traits<T>::zero();
+        }
+        break;
+    case upper_bound:
+        if (x > this->m_upper_bounds[j]) {
+            this->m_costs[j] = 1;
+            this->m_infeasibility += x - this->m_upper_bounds[j];
+        } else {
+            this->m_costs[j] = numeric_traits<T>::zero();
+        }
+        break;
+    case free_column:
+        this->m_costs[j] = numeric_traits<T>::zero();
+        break;
+    default:
+        lean_assert(false);
+        break;
+        }*/
+}
+
+
+// returns m_sign_of_alpha_r
+int lar_core_solver::column_is_out_of_bounds(unsigned j) {
+    /*
+    switch (this->m_column_type[j]) {
+    case fixed:
+    case column_type::boxed:
+        if (this->x_below_low_bound(j)) {
+            return -1;
+        }
+        if (this->x_above_upper_bound(j)) {
+            return 1;
+        }
+        return 0;
+    case low_bound:
+        if (this->x_below_low_bound(j)) {
+            return -1;
+        }
+        return 0;
+    case upper_bound:
+        if (this->x_above_upper_bound(j)) {
+            return 1;
+        }
+        return 0;
+    default:
+        return 0;
+        break;
+        }*/
+    lean_assert(false);
+    return true;
+}
+
+
+
+void lar_core_solver::calculate_pivot_row(unsigned i) {
+    lean_assert(!m_r_solver.use_tableau());
+    lean_assert(m_r_solver.m_pivot_row.is_OK());
+    m_r_solver.m_pivot_row_of_B_1.clear();
+    m_r_solver.m_pivot_row_of_B_1.resize(m_r_solver.m_m());
+    m_r_solver.m_pivot_row.clear();
+    m_r_solver.m_pivot_row.resize(m_r_solver.m_n());
+    if (m_r_solver.m_settings.use_tableau()) {
+        unsigned basis_j = m_r_solver.m_basis[i];
+        for (auto & c : m_r_solver.m_A.m_rows[i]) {
+            if (c.m_j != basis_j)
+                m_r_solver.m_pivot_row.set_value(c.get_val(), c.m_j);
+        }
+        return;
+    }
+
+    m_r_solver.calculate_pivot_row_of_B_1(i);
+    m_r_solver.calculate_pivot_row_when_pivot_row_of_B1_is_ready(i);
+}
+
+
+
+ void lar_core_solver::prefix_r() {
+     if (!m_r_solver.m_settings.use_tableau()) {
+        m_r_solver.m_copy_of_xB.resize(m_r_solver.m_n());
+        m_r_solver.m_ed.resize(m_r_solver.m_m());
+        m_r_solver.m_pivot_row.resize(m_r_solver.m_n()); 
+        m_r_solver.m_pivot_row_of_B_1.resize(m_r_solver.m_m());
+        m_r_solver.m_w.resize(m_r_solver.m_m());
+        m_r_solver.m_y.resize(m_r_solver.m_m());
+        m_r_solver.m_rows_nz.resize(m_r_solver.m_m(), 0);
+        m_r_solver.m_columns_nz.resize(m_r_solver.m_n(), 0); 
+        init_column_row_nz_for_r_solver();
+    }
+
+    m_r_solver.m_b.resize(m_r_solver.m_m());
+    if (m_r_solver.m_settings.simplex_strategy() != simplex_strategy_enum::tableau_rows) {
+        if(m_r_solver.m_settings.use_breakpoints_in_feasibility_search)
+            m_r_solver.m_breakpoint_indices_queue.resize(m_r_solver.m_n());
+        m_r_solver.m_costs.resize(m_r_solver.m_n());
+        m_r_solver.m_d.resize(m_r_solver.m_n());
+        m_r_solver.m_using_infeas_costs = true;
+    }
+}
+
+ void lar_core_solver::prefix_d() {
+    m_d_solver.m_b.resize(m_d_solver.m_m());
+    m_d_solver.m_breakpoint_indices_queue.resize(m_d_solver.m_n());
+    m_d_solver.m_copy_of_xB.resize(m_d_solver.m_n());
+    m_d_solver.m_costs.resize(m_d_solver.m_n());
+    m_d_solver.m_d.resize(m_d_solver.m_n());
+    m_d_solver.m_ed.resize(m_d_solver.m_m());
+    m_d_solver.m_pivot_row.resize(m_d_solver.m_n());
+    m_d_solver.m_pivot_row_of_B_1.resize(m_d_solver.m_m());
+    m_d_solver.m_w.resize(m_d_solver.m_m());
+    m_d_solver.m_y.resize(m_d_solver.m_m());
+    m_d_solver.m_steepest_edge_coefficients.resize(m_d_solver.m_n());
+    m_d_solver.m_column_norms.clear();
+    m_d_solver.m_column_norms.resize(m_d_solver.m_n(), 2);
+    m_d_solver.m_inf_set.clear();
+    m_d_solver.m_inf_set.resize(m_d_solver.m_n());
+}
+
+void lar_core_solver::fill_not_improvable_zero_sum_from_inf_row() {
+    lean_assert(m_r_solver.A_mult_x_is_off() == false);
+    unsigned bj = m_r_basis[m_r_solver.m_inf_row_index_for_tableau];
+    m_infeasible_sum_sign =  m_r_solver.inf_sign_of_column(bj);
+    m_infeasible_linear_combination.clear();
+    for (auto & rc : m_r_solver.m_A.m_rows[m_r_solver.m_inf_row_index_for_tableau]) {
+        m_infeasible_linear_combination.push_back(std::make_pair( rc.get_val(), rc.m_j));
+    }
+}
+
+void lar_core_solver::fill_not_improvable_zero_sum() {
+    if (m_r_solver.m_settings.simplex_strategy() == simplex_strategy_enum::tableau_rows) {
+        fill_not_improvable_zero_sum_from_inf_row();
+        return;
+    }
+    //  reusing the existing mechanism for row_feasibility_loop
+    m_infeasible_sum_sign = m_r_solver.m_settings.use_breakpoints_in_feasibility_search? -1 : 1;
+    m_infeasible_linear_combination.clear();
+    for (auto j : m_r_solver.m_basis) {
+        const mpq & cost_j = m_r_solver.m_costs[j];
+        if (!numeric_traits<mpq>::is_zero(cost_j)) {
+            m_infeasible_linear_combination.push_back(std::make_pair(cost_j, j));
+        }
+    }
+    // m_costs are expressed by m_d ( additional costs), substructing the latter gives 0
+    for (unsigned j = 0; j < m_r_solver.m_n(); j++) {
+        if (m_r_solver.m_basis_heading[j] >= 0) continue;
+        const mpq & d_j = m_r_solver.m_d[j];
+        if (!numeric_traits<mpq>::is_zero(d_j)) {
+            m_infeasible_linear_combination.push_back(std::make_pair(-d_j, j));
+        }
+    }
+}
+
+
+void lar_core_solver::solve() {
+    lean_assert(m_r_solver.non_basic_columns_are_set_correctly());
+    lean_assert(m_r_solver.inf_set_is_correct());
+    if (m_r_solver.current_x_is_feasible() && m_r_solver.m_look_for_feasible_solution_only) {
+        m_r_solver.set_status(OPTIMAL);
+        return;
+    }
+    ++settings().st().m_need_to_solve_inf;
+    lean_assert(!m_r_solver.A_mult_x_is_off());
+    lean_assert((!settings().use_tableau()) || r_basis_is_OK());
+    if (need_to_presolve_with_double_solver()) {
+        prefix_d();
+        lar_solution_signature solution_signature;
+        vector<unsigned> changes_of_basis = find_solution_signature_with_doubles(solution_signature);
+        if (m_d_solver.get_status() == TIME_EXHAUSTED) {
+            m_r_solver.set_status(TIME_EXHAUSTED);
+            return;
+        }
+        if (settings().use_tableau())
+            solve_on_signature_tableau(solution_signature, changes_of_basis);
+        else 
+            solve_on_signature(solution_signature, changes_of_basis);
+        lean_assert(!settings().use_tableau() || r_basis_is_OK());
+    } else {
+        if (!settings().use_tableau()) {
+            bool snapped = m_r_solver.snap_non_basic_x_to_bound();   
+            lean_assert(m_r_solver.non_basic_columns_are_set_correctly());
+            if (snapped)
+                m_r_solver.solve_Ax_eq_b();
+        }
+        if (m_r_solver.m_look_for_feasible_solution_only)
+            m_r_solver.find_feasible_solution();
+        else
+            m_r_solver.solve();
+        lean_assert(!settings().use_tableau() || r_basis_is_OK());
+    }
+    if (m_r_solver.get_status() == INFEASIBLE) {
+        fill_not_improvable_zero_sum();
+    } else if (m_r_solver.get_status() != UNBOUNDED) {
+        m_r_solver.set_status(OPTIMAL);
+    }
+    lean_assert(r_basis_is_OK());
+    lean_assert(m_r_solver.non_basic_columns_are_set_correctly());
+    lean_assert(m_r_solver.inf_set_is_correct());
+}
+
+
+}
+

src/util/lp/lar_core_solver_instances.cpp

@@ -0,0 +1,10 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <utility>
+#include <memory>
+#include <string>
+#include "util/vector.h"
+#include <functional>
+#include "util/lp/lar_core_solver.hpp"

src/util/lp/lar_solution_signature.h

@@ -0,0 +1,13 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include "util/debug.h"
+#include "util/lp/lp_settings.h"
+#include <unordered_map>
+namespace lean {
+typedef std::unordered_map<unsigned, non_basic_column_value_position> lar_solution_signature;
+}

src/util/lp/lar_term.h

@@ -0,0 +1,64 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/indexed_vector.h"
+namespace lean {
+struct lar_term {
+    // the term evaluates to sum of m_coeffs + m_v
+    std::unordered_map<unsigned, mpq> m_coeffs;
+    mpq m_v;
+    lar_term() {}
+    void add_to_map(unsigned j, const mpq& c) {
+        auto it = m_coeffs.find(j);
+        if (it == m_coeffs.end()) {
+            m_coeffs.emplace(j, c);
+        } else {
+            it->second += c;
+            if (is_zero(it->second))
+                m_coeffs.erase(it);
+        }
+    }
+
+    unsigned size() const { return static_cast<unsigned>(m_coeffs.size()); }
+    
+    const std::unordered_map<unsigned, mpq> & coeffs() const {
+        return m_coeffs;
+    }
+    
+    lar_term(const vector<std::pair<mpq, unsigned>>& coeffs,
+             const mpq & v) : m_v(v) {
+        for (const auto & p : coeffs) {
+            add_to_map(p.second, p.first);
+        }
+    }
+    bool operator==(const lar_term & a) const {  return false; } // take care not to create identical terms
+    bool operator!=(const lar_term & a) const {  return ! (*this == a);}
+    // some terms get used in add constraint
+    // it is the same as the offset in the m_constraints
+
+    vector<std::pair<mpq, unsigned>> coeffs_as_vector() const {
+        vector<std::pair<mpq, unsigned>> ret;
+        for (const auto & p :  m_coeffs) {
+            ret.push_back(std::make_pair(p.second, p.first));
+        }
+        return ret;
+    }
+
+    // j is the basic variable to substitute
+    void subst(unsigned j, indexed_vector<mpq> & li) {
+        auto it = m_coeffs.find(j);
+        if (it == m_coeffs.end()) return;
+        const mpq & b = it->second;
+        for (unsigned it_j :li.m_index) {
+            add_to_map(it_j, - b * li.m_data[it_j]);
+        }
+        m_coeffs.erase(it);
+    }
+    
+    bool contains(unsigned j) const {
+        return m_coeffs.find(j) != m_coeffs.end();
+    }
+};
+}

src/util/lp/linear_combination_iterator.h

@@ -0,0 +1,47 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+namespace lean {
+template <typename T>
+struct linear_combination_iterator {
+    virtual bool next(T & a, unsigned & i) = 0;
+    virtual bool next(unsigned & i) = 0;
+    virtual void reset() = 0;
+    virtual linear_combination_iterator * clone() = 0;
+    virtual ~linear_combination_iterator(){}
+    virtual unsigned size() const = 0;
+};
+template <typename T>
+struct linear_combination_iterator_on_vector : linear_combination_iterator<T> {
+    vector<std::pair<T, unsigned>> & m_vector;
+    int m_offset = 0;
+    bool next(T & a, unsigned & i) {
+        if(m_offset >= m_vector.size())
+            return false;
+        auto & p = m_vector[m_offset];
+        a = p.first;
+        i = p.second;
+        m_offset++;
+        return true;
+    }
+
+    bool next(unsigned & i) {
+        if(m_offset >= m_vector.size())
+            return false;
+        auto & p = m_vector[m_offset];
+        i = p.second;
+        m_offset++;
+        return true;
+    }
+    
+    void reset() {m_offset = 0;}
+    linear_combination_iterator<T> * clone() {
+        return new linear_combination_iterator_on_vector(m_vector);
+    }
+    linear_combination_iterator_on_vector(vector<std::pair<T, unsigned>> & vec): m_vector(vec) {}
+    unsigned size() const { return m_vector.size(); }
+};
+
+}

src/util/lp/lp_core_solver_base.h

@@ -0,0 +1,683 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include <set>
+#include "util/vector.h"
+#include <string>
+#include "util/lp/lp_utils.h"
+#include "util/lp/core_solver_pretty_printer.h"
+#include "util/lp/numeric_pair.h"
+#include "util/lp/static_matrix.h"
+#include "util/lp/lu.h"
+#include "util/lp/permutation_matrix.h"
+#include "util/lp/column_namer.h"
+namespace lean {
+
+template <typename T, typename X> // X represents the type of the x variable and the bounds
+class lp_core_solver_base {    
+    unsigned m_total_iterations = 0;
+    unsigned inc_total_iterations() { ++m_settings.st().m_total_iterations; return m_total_iterations++; }
+private:
+    lp_status m_status;
+public:
+    bool current_x_is_feasible() const { return m_inf_set.size() == 0; }
+    bool current_x_is_infeasible() const { return m_inf_set.size() != 0; }
+    int_set m_inf_set;
+    bool m_using_infeas_costs = false;
+
+
+    vector<unsigned> m_columns_nz; // m_columns_nz[i] keeps an approximate value of non zeroes the i-th column
+    vector<unsigned> m_rows_nz; // m_rows_nz[i] keeps an approximate value of non zeroes in the i-th row
+    indexed_vector<T> m_pivot_row_of_B_1;  // the pivot row of the reverse of B
+    indexed_vector<T> m_pivot_row; // this is the real pivot row of the simplex tableu
+    static_matrix<T, X> & m_A; // the matrix A
+    vector<X> & m_b; // the right side
+    vector<unsigned> & m_basis;
+    vector<unsigned>& m_nbasis;
+    vector<int>& m_basis_heading;
+    vector<X> & m_x; // a feasible solution, the fist time set in the constructor
+    vector<T> & m_costs;
+    lp_settings & m_settings;
+    vector<T> m_y; // the buffer for yB = cb
+    // a device that is able to solve Bx=c, xB=d, and change the basis
+    lu<T, X> * m_factorization = nullptr;
+    const column_namer & m_column_names;
+    indexed_vector<T> m_w; // the vector featuring in 24.3 of the Chvatal book
+    vector<T> m_d; // the vector of reduced costs
+    indexed_vector<T> m_ed; // the solution of B*m_ed = a
+    unsigned m_iters_with_no_cost_growing = 0;
+    const vector<column_type> & m_column_types;
+    const vector<X> & m_low_bounds;
+    const vector<X> & m_upper_bounds;
+    vector<T> m_column_norms; // the approximate squares of column norms that help choosing a profitable column
+    vector<X> m_copy_of_xB;
+    unsigned m_basis_sort_counter = 0;
+    vector<T> m_steepest_edge_coefficients;
+    vector<unsigned> m_trace_of_basis_change_vector; // the even positions are entering, the odd positions are leaving
+    bool m_tracing_basis_changes = false;
+    int_set* m_pivoted_rows = nullptr;
+    bool m_look_for_feasible_solution_only = false;
+    void start_tracing_basis_changes() {
+        m_trace_of_basis_change_vector.resize(0);
+        m_tracing_basis_changes = true;
+    }
+        
+    void stop_tracing_basis_changes() {
+        m_tracing_basis_changes = false;
+    }
+
+    void trace_basis_change(unsigned entering, unsigned leaving) {
+        unsigned size = m_trace_of_basis_change_vector.size();
+        if (size >= 2 && m_trace_of_basis_change_vector[size-2] == leaving
+                &&  m_trace_of_basis_change_vector[size -1] == entering) {
+            m_trace_of_basis_change_vector.pop_back();
+            m_trace_of_basis_change_vector.pop_back();
+        } else {
+            m_trace_of_basis_change_vector.push_back(entering);
+            m_trace_of_basis_change_vector.push_back(leaving);
+        }
+    }
+    
+    unsigned m_m() const { return m_A.row_count(); } // it is the length of basis. The matrix m_A has m_m rows and the dimension of the matrix A is m_m
+    unsigned m_n() const { return m_A.column_count(); } // the number of columns in the matrix m_A
+
+    lp_core_solver_base(static_matrix<T, X> & A,
+                        vector<X> & b, // the right side vector
+                        vector<unsigned> & basis,
+                        vector<unsigned> & nbasis,
+                        vector<int> & heading,
+                        vector<X> & x,
+                        vector<T> & costs,
+                        lp_settings & settings,
+                        const column_namer& column_names,
+                        const vector<column_type> & column_types,
+                        const vector<X> & low_bound_values,
+                        const vector<X> & upper_bound_values);
+
+    void allocate_basis_heading();
+    void init();
+
+    virtual ~lp_core_solver_base() {
+        if (m_factorization != nullptr)
+            delete m_factorization;
+     }
+
+    vector<unsigned> & non_basis() {
+        return m_nbasis;
+    }
+
+    const vector<unsigned> & non_basis() const { return m_nbasis; }
+
+
+    
+    void set_status(lp_status status) {
+        m_status = status;
+    }
+    lp_status get_status() const{
+        return m_status;
+    }
+
+    void fill_cb(T * y);
+
+    void fill_cb(vector<T> & y);
+
+    void solve_yB(vector<T> & y);
+
+    void solve_Bd(unsigned entering);
+
+    void solve_Bd(unsigned entering, indexed_vector<T> & column);
+
+    void pretty_print(std::ostream & out);
+
+    void save_state(T * w_buffer, T * d_buffer);
+
+    void restore_state(T * w_buffer, T * d_buffer);
+
+    X get_cost() {
+        return dot_product(m_costs, m_x);
+    }
+
+    void copy_m_w(T * buffer);
+
+    void restore_m_w(T * buffer);
+
+    // needed for debugging
+    void copy_m_ed(T * buffer);
+
+    void restore_m_ed(T * buffer);
+
+    bool A_mult_x_is_off() const;
+
+    bool A_mult_x_is_off_on_index(const vector<unsigned> & index) const;
+    // from page 182 of Istvan Maros's book
+    void calculate_pivot_row_of_B_1(unsigned pivot_row);
+
+    void calculate_pivot_row_when_pivot_row_of_B1_is_ready(unsigned pivot_row);
+
+    void update_x(unsigned entering, const X & delta);
+
+    const T & get_var_value(unsigned j) const {
+        return m_x[j];
+    }
+
+    void print_statistics(char const* str, X cost, std::ostream & message_stream);
+
+    bool print_statistics_with_iterations_and_check_that_the_time_is_over(std::ostream & message_stream);
+
+    bool print_statistics_with_iterations_and_nonzeroes_and_cost_and_check_that_the_time_is_over(char const* str, std::ostream & message_stream);
+
+    bool print_statistics_with_cost_and_check_that_the_time_is_over(X cost, std::ostream & message_stream);
+
+    unsigned total_iterations() const { return m_total_iterations; }
+
+    void set_total_iterations(unsigned s) { m_total_iterations = s; }
+
+    void set_non_basic_x_to_correct_bounds();
+
+    bool at_bound(const X &x, const X & bound) const {
+        return !below_bound(x, bound) && !above_bound(x, bound);
+    }
+
+
+    bool need_to_pivot_to_basis_tableau() const {
+        lean_assert(m_A.is_correct());
+        unsigned m = m_A.row_count();
+        for (unsigned i = 0; i < m; i++) {
+            unsigned bj = m_basis[i];
+            lean_assert(m_A.m_columns[bj].size() > 0);
+            if (m_A.m_columns[bj].size() > 1 || m_A.get_val(m_A.m_columns[bj][0]) != one_of_type<mpq>()) return true;
+        }
+        return false;
+    }
+    
+    bool reduced_costs_are_correct_tableau() const {
+        if (m_settings.simplex_strategy() == simplex_strategy_enum::tableau_rows)
+            return true;
+        lean_assert(m_A.is_correct());
+        if (m_using_infeas_costs) {
+            if (infeasibility_costs_are_correct() == false) {
+                std::cout << "infeasibility_costs_are_correct() does not hold" << std::endl;
+                return false;
+            }
+        }
+            
+        unsigned n = m_A.column_count();
+        for (unsigned j = 0; j < n; j++) {
+            if (m_basis_heading[j] >= 0) {
+                if (!is_zero(m_d[j])) {
+                    
+                    std::cout << "case a\n";
+                    print_column_info(j, std::cout);
+                    return false;
+                }
+            } else {
+                auto d = m_costs[j];
+                for (auto & cc : this->m_A.m_columns[j]) {
+                    d -= this->m_costs[this->m_basis[cc.m_i]] * this->m_A.get_val(cc);
+                }
+                if (m_d[j] != d) {
+                    std::cout << "case b\n";
+                    print_column_info(j, std::cout);
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+    
+    bool below_bound(const X & x, const X & bound) const {
+        if (precise()) return x < bound;
+        return below_bound_numeric<X>(x, bound, m_settings.primal_feasibility_tolerance);
+    }
+
+    bool above_bound(const X & x, const X & bound) const {
+        if (precise()) return x > bound;
+        return above_bound_numeric<X>(x, bound, m_settings.primal_feasibility_tolerance);
+    }
+
+    bool x_below_low_bound(unsigned p) const {
+        return below_bound(m_x[p], m_low_bounds[p]);
+    }
+
+    bool infeasibility_costs_are_correct() const;
+    bool infeasibility_cost_is_correct_for_column(unsigned j) const;
+    
+    bool x_above_low_bound(unsigned p) const {
+        return above_bound(m_x[p], m_low_bounds[p]);
+    }
+
+    bool x_below_upper_bound(unsigned p) const {
+        return below_bound(m_x[p], m_upper_bounds[p]);
+    }
+
+
+    bool x_above_upper_bound(unsigned p) const {
+        return above_bound(m_x[p], m_upper_bounds[p]);
+    }
+    bool x_is_at_low_bound(unsigned j) const {
+        return at_bound(m_x[j], m_low_bounds[j]);
+    }
+    bool x_is_at_upper_bound(unsigned j) const {
+        return at_bound(m_x[j], m_upper_bounds[j]);
+    }
+
+    bool x_is_at_bound(unsigned j) const {
+        return x_is_at_low_bound(j) || x_is_at_upper_bound(j);
+    }
+    bool column_is_feasible(unsigned j) const;
+
+    bool calc_current_x_is_feasible_include_non_basis() const;
+
+    bool inf_set_is_correct() const;
+    
+    bool column_is_dual_feasible(unsigned j) const;
+
+    bool d_is_not_negative(unsigned j) const;
+
+    bool d_is_not_positive(unsigned j) const;
+
+
+    bool time_is_over();
+
+    void rs_minus_Anx(vector<X> & rs);
+
+    bool find_x_by_solving();
+
+    bool update_basis_and_x(int entering, int leaving, X const & tt);
+
+    bool basis_has_no_doubles() const;
+
+    bool non_basis_has_no_doubles() const;
+
+    bool basis_is_correctly_represented_in_heading() const ;
+    bool non_basis_is_correctly_represented_in_heading() const ;
+
+    bool basis_heading_is_correct() const;
+
+    void restore_x_and_refactor(int entering, int leaving, X const & t);
+
+    void restore_x(unsigned entering, X const & t);
+
+    void fill_reduced_costs_from_m_y_by_rows();
+
+    void copy_rs_to_xB(vector<X> & rs);
+    virtual bool low_bounds_are_set() const { return false; }
+    X low_bound_value(unsigned j) const { return m_low_bounds[j]; }
+    X upper_bound_value(unsigned j) const { return m_upper_bounds[j]; }
+
+    column_type get_column_type(unsigned j) const {return m_column_types[j]; }
+
+    bool pivot_row_element_is_too_small_for_ratio_test(unsigned j) {
+        return m_settings.abs_val_is_smaller_than_pivot_tolerance(m_pivot_row[j]);
+    }
+
+    X bound_span(unsigned j) const {
+        return m_upper_bounds[j] - m_low_bounds[j];
+    }
+
+    std::string column_name(unsigned column) const;
+
+    void copy_right_side(vector<X> & rs);
+
+    void add_delta_to_xB(vector<X> & del);
+
+    void find_error_in_BxB(vector<X>& rs);
+
+    // recalculates the projection of x to B, such that Ax = b, whereab is the right side
+    void solve_Ax_eq_b();
+
+    bool snap_non_basic_x_to_bound() {
+        bool ret = false;
+        for (unsigned j : non_basis())
+            ret = snap_column_to_bound(j) || ret;
+        return ret;
+    }
+
+    
+    
+    bool snap_column_to_bound(unsigned j) {
+        switch (m_column_types[j]) {
+        case column_type::fixed:
+            if (x_is_at_bound(j))
+                break;
+            m_x[j] = m_low_bounds[j];
+            return true;
+        case column_type::boxed:
+            if (x_is_at_bound(j))
+                break; // we should preserve x if possible
+            // snap randomly
+            if (my_random() % 2 == 1) 
+                m_x[j] = m_low_bounds[j];
+            else
+                m_x[j] = m_upper_bounds[j];
+            return true;
+        case column_type::low_bound:
+            if (x_is_at_low_bound(j))
+                break;
+            m_x[j] = m_low_bounds[j];
+            return true;
+        case column_type::upper_bound:
+            if (x_is_at_upper_bound(j))
+                break;
+            m_x[j] = m_upper_bounds[j];
+            return true;
+        default:
+            break;
+        }
+        return false;
+    }
+
+    bool make_column_feasible(unsigned j, numeric_pair<mpq> & delta) {
+        lean_assert(m_basis_heading[j] < 0);
+        auto & x = m_x[j];
+        switch (m_column_types[j]) {
+        case column_type::fixed:
+            lean_assert(m_low_bounds[j] == m_upper_bounds[j]);
+            if (x != m_low_bounds[j]) {
+                delta = m_low_bounds[j] - x;
+                x = m_low_bounds[j];
+                return true;
+            }
+            break;
+        case column_type::boxed:
+            if (x < m_low_bounds[j]) {
+                delta = m_low_bounds[j] - x;
+                x = m_low_bounds[j];
+                return true;
+            }
+            if (x > m_upper_bounds[j]) {
+                delta = m_upper_bounds[j] - x;
+                x = m_upper_bounds[j];
+                return true;
+            }
+            break;
+        case column_type::low_bound:
+            if (x < m_low_bounds[j]) {
+                delta = m_low_bounds[j] - x;
+                x = m_low_bounds[j];
+                return true;
+            }
+            break;
+        case column_type::upper_bound:
+            if (x > m_upper_bounds[j]) {
+                delta = m_upper_bounds[j] - x;
+                x = m_upper_bounds[j];
+                return true;
+            }
+            break;
+        case column_type::free_column:
+            break;
+        default:
+            lean_assert(false);
+            break;
+        }
+        return false;
+    }
+
+    
+    void snap_non_basic_x_to_bound_and_free_to_zeroes();
+    void snap_xN_to_bounds_and_fill_xB();
+
+    void snap_xN_to_bounds_and_free_columns_to_zeroes();
+
+    void init_reduced_costs_for_one_iteration();
+
+    non_basic_column_value_position get_non_basic_column_value_position(unsigned j) const;
+
+    void init_lu();
+    int pivots_in_column_and_row_are_different(int entering, int leaving) const;
+    void pivot_fixed_vars_from_basis();
+    bool pivot_for_tableau_on_basis();
+    bool pivot_row_for_tableau_on_basis(unsigned row);
+    void init_basic_part_of_basis_heading() {
+        unsigned m = m_basis.size();
+        for (unsigned i = 0; i < m; i++) {
+            unsigned column = m_basis[i];
+            m_basis_heading[column] = i;
+        }
+    }
+
+    void init_non_basic_part_of_basis_heading() {
+        this->m_nbasis.clear();
+        for (int j = m_basis_heading.size(); j--;){
+            if (m_basis_heading[j] < 0) {
+                m_nbasis.push_back(j);
+                // the index of column j in m_nbasis is (- basis_heading[j] - 1)
+                m_basis_heading[j] = - static_cast<int>(m_nbasis.size());
+            }
+        }
+    }
+    
+    void init_basis_heading_and_non_basic_columns_vector() {
+        m_basis_heading.resize(0);
+        m_basis_heading.resize(m_n(), -1);
+        init_basic_part_of_basis_heading();
+        init_non_basic_part_of_basis_heading();
+    }
+
+    void change_basis_unconditionally(unsigned entering, unsigned leaving) {
+        lean_assert(m_basis_heading[entering] < 0);
+        int place_in_non_basis = -1 - m_basis_heading[entering];
+        if (static_cast<unsigned>(place_in_non_basis) >= m_nbasis.size()) {
+              // entering variable in not in m_nbasis, we need to put it back;
+            m_basis_heading[entering] = place_in_non_basis = m_nbasis.size();
+            m_nbasis.push_back(entering);
+        }
+        
+        int place_in_basis =  m_basis_heading[leaving];
+        m_basis_heading[entering] = place_in_basis;
+        m_basis[place_in_basis] = entering;
+        m_basis_heading[leaving] = -place_in_non_basis - 1;
+        m_nbasis[place_in_non_basis] = leaving;
+        if (m_tracing_basis_changes)
+            trace_basis_change(entering, leaving);
+        
+    }
+    
+    void change_basis(unsigned entering, unsigned leaving) {
+        lean_assert(m_basis_heading[entering] < 0);
+        
+        int place_in_basis =  m_basis_heading[leaving];
+        int place_in_non_basis = - m_basis_heading[entering] - 1;
+        m_basis_heading[entering] = place_in_basis;
+        m_basis[place_in_basis] = entering;
+
+        m_basis_heading[leaving] = -place_in_non_basis - 1;
+        m_nbasis[place_in_non_basis] = leaving;
+        
+        if (m_tracing_basis_changes)
+            trace_basis_change(entering, leaving);
+    }
+
+    void restore_basis_change(unsigned entering, unsigned leaving) {
+        if (m_basis_heading[entering] < 0) {
+            return; // the basis has not been changed
+        }
+        change_basis_unconditionally(leaving, entering);
+    }
+
+    bool non_basic_column_is_set_correctly(unsigned j) const {
+        if (j >= this->m_n())
+            return false;
+        switch (this->m_column_types[j]) {
+        case column_type::fixed:
+        case column_type::boxed:
+            if (!this->x_is_at_bound(j))
+                return false;
+            break;
+        case column_type::low_bound:
+            if (!this->x_is_at_low_bound(j))
+                return false;
+            break;
+        case column_type::upper_bound:
+            if (!this->x_is_at_upper_bound(j))
+                return false;
+            break;
+        case column_type::free_column:
+            break;
+        default:
+            lean_assert(false);
+            break;
+        }
+        return true;
+    }
+    bool non_basic_columns_are_set_correctly() const {
+        for (unsigned j : this->m_nbasis)
+            if (!column_is_feasible(j)) {
+                print_column_info(j, std::cout);
+                return false;
+            }
+        return true;
+    }
+
+    void print_column_bound_info(unsigned j, std::ostream & out) const {
+        out << column_name(j) << " type = " << column_type_to_string(m_column_types[j]) << std::endl;
+        switch (m_column_types[j]) {
+        case column_type::fixed:
+        case column_type::boxed:
+            out << "(" << m_low_bounds[j] << ", " << m_upper_bounds[j] << ")" << std::endl;
+            break;
+        case column_type::low_bound:
+            out << m_low_bounds[j] << std::endl;
+            break;
+        case column_type::upper_bound:
+            out << m_upper_bounds[j] << std::endl;
+            break;
+        default:
+            break;
+        }
+    }
+
+    void print_column_info(unsigned j, std::ostream & out) const {
+        out << "column_index = " << j << ", name = "<< column_name(j) << " type = " << column_type_to_string(m_column_types[j]) << std::endl;
+        switch (m_column_types[j]) {
+        case column_type::fixed:
+        case column_type::boxed:
+            out << "(" << m_low_bounds[j] << ", " << m_upper_bounds[j] << ")" << std::endl;
+            break;
+        case column_type::low_bound:
+            out << m_low_bounds[j] << std::endl;
+            break;
+        case column_type::upper_bound:
+            out << m_upper_bounds[j] << std::endl;
+            break;
+        case column_type::free_column:
+            break;
+        default:
+            lean_assert(false);
+        }
+        std::cout << "basis heading = " << m_basis_heading[j] << std::endl;
+        std::cout << "x = " << m_x[j] << std::endl;
+        /*
+        std::cout << "cost = " << m_costs[j] << std::endl;
+        std:: cout << "m_d = " << m_d[j] << std::endl;*/
+    }
+
+    bool column_is_free(unsigned j) { return this->m_column_type[j] == free; }
+
+    bool column_has_upper_bound(unsigned j) {
+        switch(m_column_types[j]) {
+        case column_type::free_column:
+        case column_type::low_bound:
+            return false;
+        default:
+            return true;
+        }
+    }
+
+    bool bounds_for_boxed_are_set_correctly() const {
+        for (unsigned j = 0; j < m_column_types.size(); j++) {
+            if (m_column_types[j] != column_type::boxed) continue;
+            if (m_low_bounds[j] > m_upper_bounds[j])
+                return false;
+        }
+        return true;
+    }
+    
+    bool column_has_low_bound(unsigned j) {
+        switch(m_column_types[j]) {
+        case column_type::free_column:
+        case column_type::upper_bound:
+            return false;
+        default:
+            return true;
+        }
+    }
+
+    // only check for basic columns
+    bool calc_current_x_is_feasible() const {
+        unsigned i = this->m_m();
+        while (i--) {
+            if (!column_is_feasible(m_basis[i]))
+                return false;
+        }
+        return true;
+    }
+
+    int find_pivot_index_in_row(unsigned i, const vector<column_cell> & col) const {
+        for (const auto & c: col) {
+            if (c.m_i == i)
+                return c.m_offset;
+        }
+        return -1;
+    }
+
+    void transpose_rows_tableau(unsigned i, unsigned ii);
+    
+    void pivot_to_reduced_costs_tableau(unsigned i, unsigned j);
+
+    bool pivot_column_tableau(unsigned j, unsigned row_index);
+    bool divide_row_by_pivot(unsigned pivot_row, unsigned pivot_col);
+    
+    bool precise() const { return numeric_traits<T>::precise(); }
+
+    simplex_strategy_enum simplex_strategy() const { return
+            m_settings.simplex_strategy();
+    }
+
+    bool use_tableau() const { return m_settings.use_tableau(); }
+    
+    template <typename K>
+    static void swap(vector<K> &v, unsigned i, unsigned j) {
+        auto t = v[i];
+        v[i] = v[j];
+        v[j] = t;
+    }
+        
+    // called when transposing row i and ii
+    void transpose_basis(unsigned i, unsigned ii) {
+        swap(m_basis, i, ii);
+        swap(m_basis_heading, m_basis[i], m_basis[ii]);
+    }
+
+    bool column_is_in_inf_set(unsigned j) const {
+        return m_inf_set.contains(j);
+    }
+
+    void update_column_in_inf_set(unsigned j) {
+        if (column_is_feasible(j)) {
+            m_inf_set.erase(j);
+        } else {
+            m_inf_set.insert(j);
+        }
+    }
+    void insert_column_into_inf_set(unsigned j) {
+        m_inf_set.insert(j);
+        lean_assert(!column_is_feasible(j));
+    }
+    void remove_column_from_inf_set(unsigned j) {
+        m_inf_set.erase(j);
+        lean_assert(column_is_feasible(j));
+    }
+    bool costs_on_nbasis_are_zeros() const {
+        lean_assert(this->basis_heading_is_correct());
+        for (unsigned j = 0; j < this->m_n(); j++) {
+            if (this->m_basis_heading[j] < 0)
+                lean_assert(is_zero(this->m_costs[j]));
+        }
+        return true;
+}
+};
+}

src/util/lp/lp_core_solver_base_instances.cpp

@@ -0,0 +1,131 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <utility>
+#include <memory>
+#include <string>
+#include "util/vector.h"
+#include <functional>
+#include "util/lp/lp_core_solver_base.hpp"
+template bool lean::lp_core_solver_base<double, double>::A_mult_x_is_off() const;
+template bool lean::lp_core_solver_base<double, double>::A_mult_x_is_off_on_index(const vector<unsigned> &) const;
+template bool lean::lp_core_solver_base<double, double>::basis_heading_is_correct() const;
+template void lean::lp_core_solver_base<double, double>::calculate_pivot_row_of_B_1(unsigned int);
+template void lean::lp_core_solver_base<double, double>::calculate_pivot_row_when_pivot_row_of_B1_is_ready(unsigned);
+template bool lean::lp_core_solver_base<double, double>::column_is_dual_feasible(unsigned int) const;
+template void lean::lp_core_solver_base<double, double>::fill_reduced_costs_from_m_y_by_rows();
+template bool lean::lp_core_solver_base<double, double>::find_x_by_solving();
+template lean::non_basic_column_value_position lean::lp_core_solver_base<double, double>::get_non_basic_column_value_position(unsigned int) const;
+template lean::non_basic_column_value_position lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::get_non_basic_column_value_position(unsigned int) const;
+template lean::non_basic_column_value_position lean::lp_core_solver_base<lean::mpq, lean::mpq>::get_non_basic_column_value_position(unsigned int) const;
+template void lean::lp_core_solver_base<double, double>::init_reduced_costs_for_one_iteration();
+template lean::lp_core_solver_base<double, double>::lp_core_solver_base(
+    lean::static_matrix<double, double>&, vector<double>&, 
+    vector<unsigned int >&,
+    vector<unsigned> &, vector<int> &,
+    vector<double >&, 
+    vector<double >&, 
+    lean::lp_settings&, const column_namer&, const vector<lean::column_type >&,
+    const vector<double >&,
+    const vector<double >&);
+
+template bool lean::lp_core_solver_base<double, double>::print_statistics_with_iterations_and_nonzeroes_and_cost_and_check_that_the_time_is_over(char const*, std::ostream &);
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::print_statistics_with_iterations_and_nonzeroes_and_cost_and_check_that_the_time_is_over(char const*, std::ostream &);
+template void lean::lp_core_solver_base<double, double>::restore_x(unsigned int, double const&);
+template void lean::lp_core_solver_base<double, double>::set_non_basic_x_to_correct_bounds();
+template void lean::lp_core_solver_base<double, double>::snap_xN_to_bounds_and_free_columns_to_zeroes();
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::snap_xN_to_bounds_and_free_columns_to_zeroes();
+template void lean::lp_core_solver_base<double, double>::solve_Ax_eq_b();
+template void lean::lp_core_solver_base<double, double>::solve_Bd(unsigned int);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq>>::solve_Bd(unsigned int, indexed_vector<lean::mpq>&);
+template void lean::lp_core_solver_base<double, double>::solve_yB(vector<double >&);
+template bool lean::lp_core_solver_base<double, double>::update_basis_and_x(int, int, double const&);
+template void lean::lp_core_solver_base<double, double>::update_x(unsigned int, const double&);
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::A_mult_x_is_off() const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::A_mult_x_is_off_on_index(const vector<unsigned> &) const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::basis_heading_is_correct() const ;
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::calculate_pivot_row_of_B_1(unsigned int);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::calculate_pivot_row_when_pivot_row_of_B1_is_ready(unsigned);
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::column_is_dual_feasible(unsigned int) const;
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::fill_reduced_costs_from_m_y_by_rows();
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::find_x_by_solving();
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::init_reduced_costs_for_one_iteration();
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::print_statistics_with_iterations_and_nonzeroes_and_cost_and_check_that_the_time_is_over(char const*, std::ostream &);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::restore_x(unsigned int, lean::mpq const&);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::set_non_basic_x_to_correct_bounds();
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::solve_Ax_eq_b();
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::solve_Bd(unsigned int);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::solve_yB(vector<lean::mpq>&);
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::update_basis_and_x(int, int, lean::mpq const&);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::update_x(unsigned int, const lean::mpq&);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::calculate_pivot_row_of_B_1(unsigned int);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::calculate_pivot_row_when_pivot_row_of_B1_is_ready(unsigned);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::init();
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::init_basis_heading_and_non_basic_columns_vector();
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::init_reduced_costs_for_one_iteration();
+template lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::lp_core_solver_base(lean::static_matrix<lean::mpq, lean::numeric_pair<lean::mpq> >&, vector<lean::numeric_pair<lean::mpq> >&, vector<unsigned int >&, vector<unsigned> &, vector<int> &, vector<lean::numeric_pair<lean::mpq> >&, vector<lean::mpq>&, lean::lp_settings&, const column_namer&, const vector<lean::column_type >&,
+                                                                                                   const vector<lean::numeric_pair<lean::mpq> >&,
+                                                                                                   const vector<lean::numeric_pair<lean::mpq> >&);
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::print_statistics_with_cost_and_check_that_the_time_is_over(lean::numeric_pair<lean::mpq>, std::ostream&);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::snap_xN_to_bounds_and_fill_xB();
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::solve_Bd(unsigned int);
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::update_basis_and_x(int, int, lean::numeric_pair<lean::mpq> const&);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::update_x(unsigned int, const lean::numeric_pair<lean::mpq>&);
+template lean::lp_core_solver_base<lean::mpq, lean::mpq>::lp_core_solver_base(
+                                                                              lean::static_matrix<lean::mpq, lean::mpq>&,
+                                                                              vector<lean::mpq>&,
+                                                                              vector<unsigned int >&,
+                                                                              vector<unsigned> &, vector<int> &,
+                                                                              vector<lean::mpq>&,
+                                                                              vector<lean::mpq>&,
+                                                                              lean::lp_settings&,
+                                                                              const column_namer&,
+                                                                              const vector<lean::column_type >&,
+                                                                              const vector<lean::mpq>&,
+                                                                              const vector<lean::mpq>&);
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::print_statistics_with_iterations_and_check_that_the_time_is_over(std::ostream &);
+template std::string lean::lp_core_solver_base<double, double>::column_name(unsigned int) const;
+template void lean::lp_core_solver_base<double, double>::pretty_print(std::ostream & out);
+template void lean::lp_core_solver_base<double, double>::restore_state(double*, double*);
+template void lean::lp_core_solver_base<double, double>::save_state(double*, double*);
+template std::string lean::lp_core_solver_base<lean::mpq, lean::mpq>::column_name(unsigned int) const;
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::pretty_print(std::ostream & out);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::restore_state(lean::mpq*, lean::mpq*);
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::save_state(lean::mpq*, lean::mpq*);
+template std::string lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::column_name(unsigned int) const;
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::pretty_print(std::ostream & out);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::restore_state(lean::mpq*, lean::mpq*);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::save_state(lean::mpq*, lean::mpq*);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::solve_yB(vector<lean::mpq>&);
+template void lean::lp_core_solver_base<double, double>::init_lu();
+template void lean::lp_core_solver_base<lean::mpq, lean::mpq>::init_lu();
+template int lean::lp_core_solver_base<double, double>::pivots_in_column_and_row_are_different(int, int) const;
+template int lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::pivots_in_column_and_row_are_different(int, int) const;
+template int lean::lp_core_solver_base<lean::mpq, lean::mpq>::pivots_in_column_and_row_are_different(int, int) const;
+template bool lean::lp_core_solver_base<double, double>::calc_current_x_is_feasible_include_non_basis(void)const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::calc_current_x_is_feasible_include_non_basis(void)const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::calc_current_x_is_feasible_include_non_basis() const;
+template void  lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::pivot_fixed_vars_from_basis();
+template bool lean::lp_core_solver_base<double, double>::column_is_feasible(unsigned int) const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::column_is_feasible(unsigned int) const;
+// template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::print_linear_combination_of_column_indices(vector<std::pair<lean::mpq, unsigned int>, std::allocator<std::pair<lean::mpq, unsigned int> > > const&, std::ostream&) const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::column_is_feasible(unsigned int) const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::snap_non_basic_x_to_bound();
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::init_lu();
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::A_mult_x_is_off_on_index(vector<unsigned int> const&) const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::find_x_by_solving();
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::restore_x(unsigned int, lean::numeric_pair<lean::mpq> const&);
+template bool lean::lp_core_solver_base<double, double>::pivot_for_tableau_on_basis();
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::pivot_for_tableau_on_basis();
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq>>::pivot_for_tableau_on_basis();
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq>>::pivot_column_tableau(unsigned int, unsigned int);
+template bool lean::lp_core_solver_base<double, double>::pivot_column_tableau(unsigned int, unsigned int);
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::pivot_column_tableau(unsigned int, unsigned int);
+template void lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::transpose_rows_tableau(unsigned int, unsigned int);
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::inf_set_is_correct() const;
+template bool lean::lp_core_solver_base<double, double>::inf_set_is_correct() const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq>::inf_set_is_correct() const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::numeric_pair<lean::mpq> >::infeasibility_costs_are_correct() const;
+template bool lean::lp_core_solver_base<lean::mpq, lean::mpq >::infeasibility_costs_are_correct() const;
+template bool lean::lp_core_solver_base<double, double >::infeasibility_costs_are_correct() const;

src/util/lp/lp_dual_core_solver.h

@@ -0,0 +1,197 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/lp/static_matrix.h"
+#include "util/lp/lp_core_solver_base.h"
+#include <string>
+#include <limits>
+#include <set>
+#include <algorithm>
+#include "util/vector.h"
+
+namespace lean {
+template <typename T, typename X>
+class lp_dual_core_solver:public lp_core_solver_base<T, X> {
+public:
+    vector<bool> & m_can_enter_basis;
+    int m_r; // the row of the leaving column
+    int m_p; // leaving column; that is m_p = m_basis[m_r]
+    T m_delta; // the offset of the leaving basis variable
+    int m_sign_of_alpha_r; // see page 27
+    T m_theta_D;
+    T m_theta_P;
+    int m_q;
+    // todo : replace by a vector later
+    std::set<unsigned> m_breakpoint_set; // it is F in "Progress in the dual simplex method ..."
+    std::set<unsigned> m_flipped_boxed;
+    std::set<unsigned> m_tight_set; // it is the set of all breakpoints that become tight when m_q becomes tight
+    vector<T> m_a_wave;
+    vector<T> m_betas; // m_betas[i] is approximately a square of the norm of the i-th row of the reverse of B
+    T m_harris_tolerance;
+    std::set<unsigned> m_forbidden_rows;
+
+    lp_dual_core_solver(static_matrix<T, X> & A,
+                        vector<bool> & can_enter_basis,
+                        vector<X> & b, // the right side vector
+                        vector<X> & x, // the number of elements in x needs to be at least as large as the number of columns in A
+                        vector<unsigned> & basis,
+                        vector<unsigned> & nbasis,
+                        vector<int> & heading,
+                        vector<T> & costs,
+                        vector<column_type> & column_type_array,
+                        vector<X> & low_bound_values,
+                        vector<X> & upper_bound_values,
+                        lp_settings & settings,
+                        const column_namer & column_names):
+        lp_core_solver_base<T, X>(A,
+                                  b,
+                                  basis,
+                                  nbasis,
+                                  heading,
+                                  x,
+                                  costs,
+                                  settings,
+                                  column_names,
+                                  column_type_array,
+                                  low_bound_values,
+                                  upper_bound_values),
+        m_can_enter_basis(can_enter_basis),
+        m_a_wave(this->m_m()),
+        m_betas(this->m_m()) {
+        m_harris_tolerance = numeric_traits<T>::precise()? numeric_traits<T>::zero() : T(this->m_settings.harris_feasibility_tolerance);
+        this->solve_yB(this->m_y);
+        this->init_basic_part_of_basis_heading();
+        fill_non_basis_with_only_able_to_enter_columns();
+    }
+
+    void init_a_wave_by_zeros();
+
+    void fill_non_basis_with_only_able_to_enter_columns() {
+        auto & nb = this->m_nbasis;
+        nb.reset();
+        unsigned j = this->m_n();
+        while (j--) {
+            if (this->m_basis_heading[j] >= 0 || !m_can_enter_basis[j]) continue;
+            nb.push_back(j);
+            this->m_basis_heading[j] = - static_cast<int>(nb.size());
+        }
+    }
+
+    void restore_non_basis();
+
+    bool update_basis(int entering, int leaving);
+
+    void recalculate_xB_and_d();
+
+    void recalculate_d();
+
+    void init_betas();
+
+    void adjust_xb_for_changed_xn_and_init_betas();
+
+    void start_with_initial_basis_and_make_it_dual_feasible();
+
+    bool done();
+
+    T get_edge_steepness_for_low_bound(unsigned p);
+
+    T get_edge_steepness_for_upper_bound(unsigned p);
+
+    T pricing_for_row(unsigned i);
+
+    void pricing_loop(unsigned number_of_rows_to_try, unsigned offset_in_rows);
+
+    bool advance_on_known_p();
+
+    int define_sign_of_alpha_r();
+
+    bool can_be_breakpoint(unsigned j);
+
+    void fill_breakpoint_set();
+
+    void DSE_FTran();
+    T get_delta();
+
+    void restore_d();
+
+    bool d_is_correct();
+
+    void xb_minus_delta_p_pivot_column();
+
+    void update_betas();
+
+    void apply_flips();
+
+    void snap_xN_column_to_bounds(unsigned j);
+
+    void snap_xN_to_bounds();
+
+    void init_beta_precisely(unsigned i);
+
+    void init_betas_precisely();
+
+    // step 7 of the algorithm from Progress
+    bool basis_change_and_update();
+
+    void revert_to_previous_basis();
+
+    non_basic_column_value_position m_entering_boundary_position;
+    bool update_basis_and_x_local(int entering, int leaving, X const & tt);
+    void recover_leaving();
+
+    bool problem_is_dual_feasible() const;
+
+    bool snap_runaway_nonbasic_column(unsigned);
+
+    bool snap_runaway_nonbasic_columns();
+
+    unsigned get_number_of_rows_to_try_for_leaving();
+
+    void update_a_wave(const T & del, unsigned j) {
+        this->m_A.add_column_to_vector(del, j, & m_a_wave[0]);
+    }
+
+    bool delta_keeps_the_sign(int initial_delta_sign, const T & delta);
+
+    void set_status_to_tentative_dual_unbounded_or_dual_unbounded();
+
+    // it is positive if going from low bound to upper bound and negative if going from upper bound to low bound
+    T signed_span_of_boxed(unsigned j) {
+        return this->x_is_at_low_bound(j)? this->bound_span(j): - this->bound_span(j);
+    }
+
+    void add_tight_breakpoints_and_q_to_flipped_set();
+
+    T delta_lost_on_flips_of_tight_breakpoints();
+
+    bool tight_breakpoinst_are_all_boxed();
+
+    T calculate_harris_delta_on_breakpoint_set();
+
+    void fill_tight_set_on_harris_delta(const T & harris_delta );
+
+    void find_q_on_tight_set();
+
+    void find_q_and_tight_set();
+
+    void erase_tight_breakpoints_and_q_from_breakpoint_set();
+
+    bool ratio_test();
+
+    void process_flipped();
+    void update_d_and_xB();
+
+    void calculate_beta_r_precisely();
+    // see "Progress in the dual simplex method for large scale LP problems: practical dual phase 1 algorithms"
+
+    void update_xb_after_bound_flips();
+
+    void one_iteration();
+
+    void solve();
+
+    bool low_bounds_are_set() const { return true; }
+};
+}

src/util/lp/lp_dual_core_solver.hpp

@@ -0,0 +1,743 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <algorithm>
+#include <string>
+#include "util/vector.h"
+#include "util/lp/lp_dual_core_solver.h"
+
+namespace lean {
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::init_a_wave_by_zeros() {
+    unsigned j = this->m_m();
+    while (j--) {
+        m_a_wave[j] = numeric_traits<T>::zero();
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::restore_non_basis() {
+    auto & nb = this->m_nbasis;
+    nb.reset();
+    unsigned j = this->m_n();
+    while (j--) {
+        if (this->m_basis_heading[j] >= 0 ) continue;
+        if (m_can_enter_basis[j]) {
+            lean_assert(std::find(nb.begin(), nb.end(), j) == nb.end());
+            nb.push_back(j);
+            this->m_basis_heading[j] = - static_cast<int>(nb.size());
+        }
+    }
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::update_basis(int entering, int leaving) {
+    // the second argument is the element of the entering column from the pivot row - its value should be equal to the low diagonal element of the bump after all pivoting is done
+    if (this->m_refactor_counter++ < 200) {
+        this->m_factorization->replace_column(this->m_ed[this->m_factorization->basis_heading(leaving)], this->m_w);
+        if (this->m_factorization->get_status() == LU_status::OK) {
+            this->m_factorization->change_basis(entering, leaving);
+            return true;
+        }
+    }
+    // need to refactor
+    this->m_factorization->change_basis(entering, leaving);
+    init_factorization(this->m_factorization, this->m_A, this->m_basis, this->m_basis_heading, this->m_settings);
+    this->m_refactor_counter = 0;
+    if (this->m_factorization->get_status() != LU_status::OK) {
+        LP_OUT(this->m_settings, "failing refactor for entering = " << entering << ", leaving = " << leaving << " total_iterations = " << this->total_iterations() << std::endl);
+        this->m_iters_with_no_cost_growing++;
+        return false;
+    }
+    return true;
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::recalculate_xB_and_d() {
+    this->solve_Ax_eq_b();
+    recalculate_d();
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::recalculate_d() {
+    this->solve_yB(this->m_y);
+    this->fill_reduced_costs_from_m_y_by_rows();
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::init_betas() {
+    // todo : look at page 194 of Progress in the dual simplex algorithm for solving large scale LP problems : techniques for a fast and stable implementation
+    // the current implementation is not good enough: todo
+    unsigned i = this->m_m();
+    while (i--) {
+        m_betas[i] = 1;
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::adjust_xb_for_changed_xn_and_init_betas() {
+    this->solve_Ax_eq_b();
+    init_betas();
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::start_with_initial_basis_and_make_it_dual_feasible() {
+    this->set_non_basic_x_to_correct_bounds(); // It is not an efficient version, see 3.29,
+    // however this version does not require that m_x is the solution of Ax = 0 beforehand
+    adjust_xb_for_changed_xn_and_init_betas();
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::done() {
+    if (this->get_status() == OPTIMAL) {
+        return true;
+    }
+    if (this->total_iterations() > this->m_settings.max_total_number_of_iterations) { // debug !!!!
+        this->set_status(ITERATIONS_EXHAUSTED);
+        return true;
+    }
+    return false; // todo, need to be more cases
+}
+
+template <typename T, typename X> T lp_dual_core_solver<T, X>::get_edge_steepness_for_low_bound(unsigned p) {
+    lean_assert(this->m_basis_heading[p] >= 0 && static_cast<unsigned>(this->m_basis_heading[p]) < this->m_m());
+    T del = this->m_x[p] - this->m_low_bounds[p];
+    del *= del;
+    return del / this->m_betas[this->m_basis_heading[p]];
+}
+
+template <typename T, typename X> T lp_dual_core_solver<T, X>::get_edge_steepness_for_upper_bound(unsigned p) {
+    lean_assert(this->m_basis_heading[p] >= 0 && static_cast<unsigned>(this->m_basis_heading[p]) < this->m_m());
+    T del = this->m_x[p] - this->m_upper_bounds[p];
+    del *= del;
+    return del / this->m_betas[this->m_basis_heading[p]];
+}
+
+template <typename T, typename X> T lp_dual_core_solver<T, X>::pricing_for_row(unsigned i) {
+    unsigned p = this->m_basis[i];
+    switch (this->m_column_types[p]) {
+    case column_type::fixed:
+    case column_type::boxed:
+        if (this->x_below_low_bound(p)) {
+            T del =  get_edge_steepness_for_low_bound(p);
+            return del;
+        }
+        if (this->x_above_upper_bound(p)) {
+            T del =  get_edge_steepness_for_upper_bound(p);
+            return del;
+        }
+        return numeric_traits<T>::zero();
+    case column_type::low_bound:
+        if (this->x_below_low_bound(p)) {
+            T del =  get_edge_steepness_for_low_bound(p);
+            return del;
+        }
+        return numeric_traits<T>::zero();
+        break;
+    case column_type::upper_bound:
+        if (this->x_above_upper_bound(p)) {
+            T del =  get_edge_steepness_for_upper_bound(p);
+            return del;
+        }
+        return numeric_traits<T>::zero();
+        break;
+    case column_type::free_column:
+        lean_assert(numeric_traits<T>::is_zero(this->m_d[p]));
+        return numeric_traits<T>::zero();
+    default:
+        lean_unreachable();
+    }
+    lean_unreachable();
+    return numeric_traits<T>::zero();
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::pricing_loop(unsigned number_of_rows_to_try, unsigned offset_in_rows) {
+    m_r = -1;
+    T steepest_edge_max = numeric_traits<T>::zero();
+    unsigned initial_offset_in_rows = offset_in_rows;
+    unsigned i = offset_in_rows;
+    unsigned rows_left = number_of_rows_to_try;
+    do  {
+        if (m_forbidden_rows.find(i) != m_forbidden_rows.end()) {
+            if (++i == this->m_m()) {
+                i = 0;
+            }
+            continue;
+        }
+        T se = pricing_for_row(i);
+        if (se > steepest_edge_max) {
+            steepest_edge_max = se;
+            m_r = i;
+            if (rows_left > 0) {
+                rows_left--;
+            }
+        }
+        if (++i == this->m_m()) {
+            i = 0;
+        }
+    } while (i != initial_offset_in_rows && rows_left);
+    if (m_r == -1) {
+        if (this->get_status() != UNSTABLE) {
+            this->set_status(OPTIMAL);
+        }
+    } else {
+        m_p = this->m_basis[m_r];
+        m_delta = get_delta();
+        if (advance_on_known_p()){
+            m_forbidden_rows.clear();
+            return;
+        }
+        // failure in advance_on_known_p
+        if (this->get_status() == FLOATING_POINT_ERROR) {
+            return;
+        }
+        this->set_status(UNSTABLE);
+        m_forbidden_rows.insert(m_r);
+    }
+}
+
+    // this calculation is needed for the steepest edge update,
+    // it hijackes m_pivot_row_of_B_1 for this purpose since we will need it anymore to the end of the cycle
+template <typename T, typename X> void lp_dual_core_solver<T, X>::DSE_FTran() { // todo, see algorithm 7 from page 35
+    this->m_factorization->solve_By_for_T_indexed_only(this->m_pivot_row_of_B_1, this->m_settings);
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::advance_on_known_p() {
+    if (done()) {
+        return true;
+    }
+    this->calculate_pivot_row_of_B_1(m_r);
+    this->calculate_pivot_row_when_pivot_row_of_B1_is_ready(m_r);
+    if (!ratio_test()) {
+        return true;
+    }
+    calculate_beta_r_precisely();
+    this->solve_Bd(m_q); // FTRAN
+    int pivot_compare_result = this->pivots_in_column_and_row_are_different(m_q, m_p);
+    if (!pivot_compare_result){;}
+    else if (pivot_compare_result == 2) { // the sign is changed, cannot continue
+        lean_unreachable(); // not implemented yet
+    } else {
+        lean_assert(pivot_compare_result == 1);
+        this->init_lu();
+    }
+    DSE_FTran();
+    return basis_change_and_update();
+}
+
+template <typename T, typename X> int lp_dual_core_solver<T, X>::define_sign_of_alpha_r() {
+    switch (this->m_column_types[m_p]) {
+    case column_type::boxed:
+    case column_type::fixed:
+        if (this->x_below_low_bound(m_p)) {
+            return -1;
+        }
+        if (this->x_above_upper_bound(m_p)) {
+            return 1;
+        }
+        lean_unreachable();
+    case column_type::low_bound:
+        if (this->x_below_low_bound(m_p)) {
+            return -1;
+        }
+        lean_unreachable();
+    case column_type::upper_bound:
+        if (this->x_above_upper_bound(m_p)) {
+            return 1;
+        }
+        lean_unreachable();
+    default:
+        lean_unreachable();
+    }
+    lean_unreachable();
+    return 0;
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::can_be_breakpoint(unsigned j) {
+    if (this->pivot_row_element_is_too_small_for_ratio_test(j)) return false;
+    switch (this->m_column_types[j]) {
+    case column_type::low_bound:
+        lean_assert(this->m_settings.abs_val_is_smaller_than_harris_tolerance(this->m_x[j] - this->m_low_bounds[j]));
+        return m_sign_of_alpha_r * this->m_pivot_row[j]  > 0;
+    case column_type::upper_bound:
+        lean_assert(this->m_settings.abs_val_is_smaller_than_harris_tolerance(this->m_x[j] - this->m_upper_bounds[j]));
+        return m_sign_of_alpha_r * this->m_pivot_row[j] < 0;
+    case column_type::boxed:
+        {
+            bool low_bound = this->x_is_at_low_bound(j);
+            bool grawing = m_sign_of_alpha_r * this->m_pivot_row[j] > 0;
+            return low_bound == grawing;
+        }
+    case column_type::fixed: // is always dual feasible so we ingore it
+        return false;
+    case column_type::free_column:
+        return true;
+    default:
+        return false;
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::fill_breakpoint_set() {
+    m_breakpoint_set.clear();
+    for (unsigned j : this->non_basis()) {
+        if (can_be_breakpoint(j)) {
+            m_breakpoint_set.insert(j);
+        }
+    }
+}
+
+// template <typename T, typename X> void lp_dual_core_solver<T, X>::FTran() {
+//     this->solve_Bd(m_q);
+// }
+
+template <typename T, typename X> T lp_dual_core_solver<T, X>::get_delta() {
+    switch (this->m_column_types[m_p]) {
+    case column_type::boxed:
+        if (this->x_below_low_bound(m_p)) {
+            return this->m_x[m_p] - this->m_low_bounds[m_p];
+        }
+        if (this->x_above_upper_bound(m_p)) {
+            return this->m_x[m_p] - this->m_upper_bounds[m_p];
+        }
+        lean_unreachable();
+    case column_type::low_bound:
+        if (this->x_below_low_bound(m_p)) {
+            return this->m_x[m_p] - this->m_low_bounds[m_p];
+        }
+        lean_unreachable();
+    case column_type::upper_bound:
+        if (this->x_above_upper_bound(m_p)) {
+            return get_edge_steepness_for_upper_bound(m_p);
+        }
+        lean_unreachable();
+    case column_type::fixed:
+        return this->m_x[m_p] - this->m_upper_bounds[m_p];
+    default:
+        lean_unreachable();
+    }
+    lean_unreachable();
+    return zero_of_type<T>();
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::restore_d() {
+    this->m_d[m_p] = numeric_traits<T>::zero();
+    for (auto j : this->non_basis()) {
+        this->m_d[j] += m_theta_D * this->m_pivot_row[j];
+    }
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::d_is_correct() {
+    this->solve_yB(this->m_y);
+    for  (auto j : this->non_basis()) {
+        T d = this->m_costs[j] -  this->m_A.dot_product_with_column(this->m_y, j);
+        if (numeric_traits<T>::get_double(abs(d - this->m_d[j])) >= 0.001) {
+            LP_OUT(this->m_settings, "total_iterations = " << this->total_iterations() << std::endl
+                << "d[" << j << "] = " << this->m_d[j] << " but should be " << d << std::endl);
+            return false;
+        }
+    }
+    return true;
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::xb_minus_delta_p_pivot_column() {
+    unsigned i = this->m_m();
+    while (i--) {
+        this->m_x[this->m_basis[i]] -= m_theta_P * this->m_ed[i];
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::update_betas() { // page 194 of Progress ... todo - once in a while betas have to be reinitialized
+    T one_over_arq = numeric_traits<T>::one() / this->m_pivot_row[m_q];
+    T beta_r = this->m_betas[m_r] = std::max(T(0.0001), (m_betas[m_r] * one_over_arq) *  one_over_arq);
+    T k = -2 * one_over_arq;
+    unsigned i = this->m_m();
+    while (i--) {
+        if (static_cast<int>(i) == m_r) continue;
+        T a = this->m_ed[i];
+        m_betas[i] += a * (a * beta_r + k * this->m_pivot_row_of_B_1[i]);
+        if (m_betas[i] < T(0.0001))
+            m_betas[i] = T(0.0001);
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::apply_flips() {
+    for (unsigned j : m_flipped_boxed) {
+        lean_assert(this->x_is_at_bound(j));
+        if (this->x_is_at_low_bound(j)) {
+            this->m_x[j] = this->m_upper_bounds[j];
+        } else {
+            this->m_x[j] = this->m_low_bounds[j];
+        }
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::snap_xN_column_to_bounds(unsigned j) {
+    switch (this->m_column_type[j]) {
+    case column_type::fixed:
+        this->m_x[j] = this->m_low_bounds[j];
+        break;
+    case column_type::boxed:
+        if (this->x_is_at_low_bound(j)) {
+            this->m_x[j] = this->m_low_bounds[j];
+        } else {
+            this->m_x[j] = this->m_upper_bounds[j];
+        }
+        break;
+    case column_type::low_bound:
+        this->m_x[j] = this->m_low_bounds[j];
+        break;
+    case column_type::upper_bound:
+        this->m_x[j] = this->m_upper_bounds[j];
+        break;
+    case column_type::free_column:
+        break;
+    default:
+        lean_unreachable();
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::snap_xN_to_bounds() {
+    for (auto j : this->non_basis()) {
+        snap_xN_column_to_bounds(j);
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::init_beta_precisely(unsigned i) {
+    vector<T> vec(this->m_m(), numeric_traits<T>::zero());
+    vec[i] = numeric_traits<T>::one();
+    this->m_factorization->solve_yB_with_error_check(vec, this->m_basis);
+    T beta = numeric_traits<T>::zero();
+    for (T & v : vec) {
+        beta += v * v;
+    }
+    this->m_betas[i] =beta;
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::init_betas_precisely() {
+    unsigned i = this->m_m();
+    while (i--) {
+        init_beta_precisely(i);
+    }
+}
+
+// step 7 of the algorithm from Progress
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::basis_change_and_update() {
+    update_betas();
+    update_d_and_xB();
+    //    m_theta_P = m_delta / this->m_ed[m_r];
+    m_theta_P = m_delta / this->m_pivot_row[m_q];
+    //    xb_minus_delta_p_pivot_column();
+    apply_flips();
+    if (!this->update_basis_and_x(m_q, m_p, m_theta_P)) {
+          init_betas_precisely();
+          return false;
+    }
+
+    if (snap_runaway_nonbasic_column(m_p)) {
+        if (!this->find_x_by_solving()) {
+            revert_to_previous_basis();
+            this->m_iters_with_no_cost_growing++;
+            return false;
+        }
+    }
+
+    if (!problem_is_dual_feasible()) {
+        // todo : shift the costs!!!!
+        revert_to_previous_basis();
+        this->m_iters_with_no_cost_growing++;
+        return false;
+    }
+
+    lean_assert(d_is_correct());
+    return true;
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::recover_leaving() {
+    switch (m_entering_boundary_position) {
+    case at_low_bound:
+    case at_fixed:
+        this->m_x[m_q] = this->m_low_bounds[m_q];
+        break;
+    case at_upper_bound:
+        this->m_x[m_q] = this->m_upper_bounds[m_q];
+        break;
+    case free_of_bounds:
+        this->m_x[m_q] = zero_of_type<X>();
+    default:
+        lean_unreachable();
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::revert_to_previous_basis() {
+    LP_OUT(this->m_settings, "revert to previous basis on ( " << m_p << ", " << m_q << ")" << std::endl);
+    this->change_basis_unconditionally(m_p, m_q);
+    init_factorization(this->m_factorization, this->m_A, this->m_basis, this->m_settings);
+    if (this->m_factorization->get_status() != LU_status::OK) {
+        this->set_status(FLOATING_POINT_ERROR); // complete failure
+        return;
+    }
+    recover_leaving();
+    if (!this->find_x_by_solving()) {
+        this->set_status(FLOATING_POINT_ERROR);
+        return;
+    }
+    recalculate_xB_and_d();
+    init_betas_precisely();
+}
+
+// returns true if the column has been snapped
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::snap_runaway_nonbasic_column(unsigned j) {
+    switch (this->m_column_types[j]) {
+    case column_type::fixed:
+    case column_type::low_bound:
+        if (!this->x_is_at_low_bound(j)) {
+            this->m_x[j] = this->m_low_bounds[j];
+            return true;
+        }
+        break;
+    case column_type::boxed:
+        {
+            bool closer_to_low_bound = abs(this->m_low_bounds[j] - this->m_x[j]) < abs(this->m_upper_bounds[j] - this->m_x[j]);
+            if (closer_to_low_bound) {
+                if (!this->x_is_at_low_bound(j)) {
+                    this->m_x[j] = this->m_low_bounds[j];
+                    return true;
+                }
+            } else {
+                if (!this->x_is_at_upper_bound(j)) {
+                    this->m_x[j] = this->m_low_bounds[j];
+                    return true;
+                }
+            }
+        }
+        break;
+    case column_type::upper_bound:
+        if (!this->x_is_at_upper_bound(j)) {
+            this->m_x[j] = this->m_upper_bounds[j];
+            return true;
+        }
+        break;
+    default:
+        break;
+    }
+    return false;
+}
+
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::problem_is_dual_feasible() const {
+    for (unsigned j : this->non_basis()){
+        if (!this->column_is_dual_feasible(j)) {
+            // std::cout << "column " << j << " is not dual feasible" << std::endl;
+            // std::cout << "m_d[" << j << "] = " << this->m_d[j] << std::endl;
+            // std::cout << "x[" << j << "] = " << this->m_x[j] << std::endl;
+            // std::cout << "type = " << column_type_to_string(this->m_column_type[j]) << std::endl;
+            // std::cout << "bounds = " << this->m_low_bounds[j] << "," << this->m_upper_bounds[j] << std::endl;
+            // std::cout << "total_iterations = " << this->total_iterations() << std::endl;
+            return false;
+        }
+    }
+    return true;
+}
+
+template <typename T, typename X> unsigned lp_dual_core_solver<T, X>::get_number_of_rows_to_try_for_leaving() {
+    unsigned s = this->m_m();
+    if (this->m_m() > 300) {
+        s = (unsigned)((s / 100.0) * this->m_settings.percent_of_entering_to_check);
+    }
+    return my_random() % s + 1;
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::delta_keeps_the_sign(int initial_delta_sign, const T & delta) {
+    if (numeric_traits<T>::precise())
+        return ((delta > numeric_traits<T>::zero()) && (initial_delta_sign == 1)) ||
+            ((delta < numeric_traits<T>::zero()) && (initial_delta_sign == -1));
+
+    double del = numeric_traits<T>::get_double(delta);
+    return ( (del > this->m_settings.zero_tolerance) && (initial_delta_sign == 1)) ||
+        ((del < - this->m_settings.zero_tolerance) && (initial_delta_sign == -1));
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::set_status_to_tentative_dual_unbounded_or_dual_unbounded() {
+    if (this->get_status() == TENTATIVE_DUAL_UNBOUNDED) {
+        this->set_status(DUAL_UNBOUNDED);
+    } else {
+        this->set_status(TENTATIVE_DUAL_UNBOUNDED);
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::add_tight_breakpoints_and_q_to_flipped_set() {
+    m_flipped_boxed.insert(m_q);
+    for (auto j : m_tight_set) {
+        m_flipped_boxed.insert(j);
+    }
+}
+
+template <typename T, typename X> T lp_dual_core_solver<T, X>::delta_lost_on_flips_of_tight_breakpoints() {
+    T ret = abs(this->bound_span(m_q) * this->m_pivot_row[m_q]);
+    for (auto j : m_tight_set) {
+        ret += abs(this->bound_span(j) * this->m_pivot_row[j]);
+    }
+    return ret;
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::tight_breakpoinst_are_all_boxed() {
+    if (this->m_column_types[m_q] != column_type::boxed) return false;
+    for (auto j : m_tight_set) {
+        if (this->m_column_types[j] != column_type::boxed) return false;
+    }
+    return true;
+}
+
+template <typename T, typename X> T lp_dual_core_solver<T, X>::calculate_harris_delta_on_breakpoint_set() {
+    bool first_time = true;
+    T ret = zero_of_type<T>();
+    lean_assert(m_breakpoint_set.size() > 0);
+    for (auto j : m_breakpoint_set) {
+        T t;
+        if (this->x_is_at_low_bound(j)) {
+            t = abs((std::max(this->m_d[j], numeric_traits<T>::zero()) + m_harris_tolerance) / this->m_pivot_row[j]);
+        } else {
+            t = abs((std::min(this->m_d[j], numeric_traits<T>::zero()) - m_harris_tolerance) / this->m_pivot_row[j]);
+        }
+        if (first_time) {
+            ret = t;
+            first_time = false;
+        } else if (t < ret) {
+            ret = t;
+        }
+    }
+    return ret;
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::fill_tight_set_on_harris_delta(const T & harris_delta ){
+    m_tight_set.clear();
+    for (auto j : m_breakpoint_set) {
+        if (this->x_is_at_low_bound(j)) {
+            if (abs(std::max(this->m_d[j], numeric_traits<T>::zero()) / this->m_pivot_row[j]) <= harris_delta){
+                m_tight_set.insert(j);
+            }
+        } else {
+            if (abs(std::min(this->m_d[j], numeric_traits<T>::zero() ) / this->m_pivot_row[j]) <= harris_delta){
+                m_tight_set.insert(j);
+            }
+        }
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::find_q_on_tight_set() {
+    m_q = -1;
+    T max_pivot;
+    for (auto j : m_tight_set) {
+        T r = abs(this->m_pivot_row[j]);
+        if (m_q != -1) {
+            if (r > max_pivot) {
+                max_pivot = r;
+                m_q = j;
+            }
+        } else {
+            max_pivot = r;
+            m_q = j;
+        }
+    }
+    m_tight_set.erase(m_q);
+    lean_assert(m_q != -1);
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::find_q_and_tight_set() {
+    T harris_del = calculate_harris_delta_on_breakpoint_set();
+    fill_tight_set_on_harris_delta(harris_del);
+    find_q_on_tight_set();
+    m_entering_boundary_position = this->get_non_basic_column_value_position(m_q);
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::erase_tight_breakpoints_and_q_from_breakpoint_set() {
+    m_breakpoint_set.erase(m_q);
+    for (auto j : m_tight_set) {
+        m_breakpoint_set.erase(j);
+    }
+}
+
+template <typename T, typename X> bool lp_dual_core_solver<T, X>::ratio_test() {
+    m_sign_of_alpha_r = define_sign_of_alpha_r();
+    fill_breakpoint_set();
+    m_flipped_boxed.clear();
+    int initial_delta_sign = m_delta >= numeric_traits<T>::zero()? 1: -1;
+    do {
+        if (m_breakpoint_set.size() == 0) {
+            set_status_to_tentative_dual_unbounded_or_dual_unbounded();
+            return false;
+        }
+        this->set_status(FEASIBLE);
+        find_q_and_tight_set();
+        if (!tight_breakpoinst_are_all_boxed())  break;
+        T del = m_delta - delta_lost_on_flips_of_tight_breakpoints() * initial_delta_sign;
+        if (!delta_keeps_the_sign(initial_delta_sign, del)) break;
+        if (m_tight_set.size() + 1 == m_breakpoint_set.size()) {
+            break; // deciding not to flip since we might get stuck without finding m_q, the column entering the basis
+        }
+        // we can flip m_q together with the tight set and look for another breakpoint candidate for m_q and another tight set
+        add_tight_breakpoints_and_q_to_flipped_set();
+        m_delta = del;
+        erase_tight_breakpoints_and_q_from_breakpoint_set();
+    } while (true);
+    m_theta_D = this->m_d[m_q] / this->m_pivot_row[m_q];
+    return true;
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::process_flipped() {
+    init_a_wave_by_zeros();
+    for (auto j : m_flipped_boxed) {
+        update_a_wave(signed_span_of_boxed(j), j);
+    }
+}
+template <typename T, typename X> void lp_dual_core_solver<T, X>::update_d_and_xB() {
+    for (auto j : this->non_basis()) {
+        this->m_d[j] -= m_theta_D * this->m_pivot_row[j];
+    }
+    this->m_d[m_p] = - m_theta_D;
+    if (m_flipped_boxed.size() > 0) {
+        process_flipped();
+        update_xb_after_bound_flips();
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::calculate_beta_r_precisely() {
+    T t = numeric_traits<T>::zero();
+    unsigned i = this->m_m();
+    while (i--) {
+        T b = this->m_pivot_row_of_B_1[i];
+        t += b * b;
+    }
+    m_betas[m_r] = t;
+}
+// see "Progress in the dual simplex method for large scale LP problems: practical dual phase 1 algorithms"
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::update_xb_after_bound_flips() {
+    this->m_factorization->solve_By(m_a_wave);
+    unsigned i = this->m_m();
+    while (i--) {
+        this->m_x[this->m_basis[i]] -= m_a_wave[i];
+    }
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::one_iteration() {
+    unsigned number_of_rows_to_try = get_number_of_rows_to_try_for_leaving();
+    unsigned offset_in_rows = my_random() % this->m_m();
+    if (this->get_status() == TENTATIVE_DUAL_UNBOUNDED) {
+        number_of_rows_to_try = this->m_m();
+    } else {
+        this->set_status(FEASIBLE);
+    }
+    pricing_loop(number_of_rows_to_try, offset_in_rows);
+    lean_assert(problem_is_dual_feasible());
+}
+
+template <typename T, typename X> void lp_dual_core_solver<T, X>::solve() { // see the page 35
+    lean_assert(d_is_correct());
+    lean_assert(problem_is_dual_feasible());
+    lean_assert(this->basis_heading_is_correct());
+    this->set_total_iterations(0);
+    this->m_iters_with_no_cost_growing = 0;
+    do {
+        if (this->print_statistics_with_iterations_and_nonzeroes_and_cost_and_check_that_the_time_is_over("", *this->m_settings.get_message_ostream())){
+            return;
+        }
+        one_iteration();
+    } while (this->get_status() != FLOATING_POINT_ERROR && this->get_status() != DUAL_UNBOUNDED && this->get_status() != OPTIMAL &&
+             this->m_iters_with_no_cost_growing <= this->m_settings.max_number_of_iterations_with_no_improvements
+             && this->total_iterations() <= this->m_settings.max_total_number_of_iterations);
+}
+}

src/util/lp/lp_dual_core_solver_instances.cpp

@@ -0,0 +1,29 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <utility>
+#include <memory>
+#include <string>
+#include "util/vector.h"
+#include <functional>
+#include "util/lp/lp_dual_core_solver.hpp"
+template void lean::lp_dual_core_solver<lean::mpq, lean::mpq>::start_with_initial_basis_and_make_it_dual_feasible();
+template void lean::lp_dual_core_solver<lean::mpq, lean::mpq>::solve();
+template lean::lp_dual_core_solver<double, double>::lp_dual_core_solver(lean::static_matrix<double, double>&, vector<bool>&,
+                                                                        vector<double>&,
+                                                                        vector<double>&,
+                                                                        vector<unsigned int>&,
+                                                                        vector<unsigned> &,
+                                                                        vector<int> &,
+                                                                        vector<double>&,
+                                                                        vector<lean::column_type>&,
+                                                                        vector<double>&,
+                                                                        vector<double>&,
+                                                                        lean::lp_settings&, const lean::column_namer&);
+template void lean::lp_dual_core_solver<double, double>::start_with_initial_basis_and_make_it_dual_feasible();
+template void lean::lp_dual_core_solver<double, double>::solve();
+template void lean::lp_dual_core_solver<lean::mpq, lean::mpq>::restore_non_basis();
+template void lean::lp_dual_core_solver<double, double>::restore_non_basis();
+template void lean::lp_dual_core_solver<double, double>::revert_to_previous_basis();
+template void lean::lp_dual_core_solver<lean::mpq, lean::mpq>::revert_to_previous_basis();

src/util/lp/lp_dual_simplex.h

@@ -0,0 +1,79 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/vector.h"
+#include "util/lp/lp_utils.h"
+#include "util/lp/lp_solver.h"
+#include "util/lp/lp_dual_core_solver.h"
+namespace lean {
+
+template <typename T, typename X>
+class lp_dual_simplex: public lp_solver<T, X> {
+    lp_dual_core_solver<T, X> * m_core_solver = nullptr;
+    vector<T> m_b_copy;
+    vector<T> m_low_bounds; // We don't have a convention here that all low bounds are zeros. At least it does not hold for the first stage solver
+    vector<column_type> m_column_types_of_core_solver;
+    vector<column_type> m_column_types_of_logicals;
+    vector<bool>  m_can_enter_basis;
+public:
+    ~lp_dual_simplex() {
+        if (m_core_solver != nullptr) {
+            delete m_core_solver;
+        }
+    }
+
+
+
+    void decide_on_status_after_stage1();
+
+    void fix_logical_for_stage2(unsigned j);
+
+    void fix_structural_for_stage2(unsigned j);
+
+    void unmark_boxed_and_fixed_columns_and_fix_structural_costs();
+
+    void restore_right_sides();
+
+    void solve_for_stage2();
+
+    void fill_x_with_zeros();
+
+    void stage1();
+
+    void stage2();
+
+    void fill_first_stage_solver_fields();
+
+    column_type get_column_type(unsigned j);
+
+    void fill_costs_bounds_types_and_can_enter_basis_for_the_first_stage_solver_structural_column(unsigned j);
+
+    void fill_costs_bounds_types_and_can_enter_basis_for_the_first_stage_solver_logical_column(unsigned j);
+
+    void fill_costs_and_bounds_and_column_types_for_the_first_stage_solver();
+
+    void set_type_for_logical(unsigned j, column_type col_type) {
+        this->m_column_types_of_logicals[j - this->number_of_core_structurals()] = col_type;
+    }
+
+    void fill_first_stage_solver_fields_for_row_slack_and_artificial(unsigned row,
+                                                              unsigned & slack_var,
+                                                                     unsigned & artificial);
+
+    void augment_matrix_A_and_fill_x_and_allocate_some_fields();
+
+
+
+    void copy_m_b_aside_and_set_it_to_zeros();
+
+    void find_maximal_solution();
+
+    virtual T get_column_value(unsigned column) const {
+        return this->get_column_value_with_core_solver(column, m_core_solver);
+    }
+
+    T get_current_cost() const;
+};
+}

src/util/lp/lp_dual_simplex.hpp

@@ -0,0 +1,362 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/lp_dual_simplex.h"
+namespace lean{
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::decide_on_status_after_stage1() {
+    switch (m_core_solver->get_status()) {
+    case OPTIMAL:
+        if (this->m_settings.abs_val_is_smaller_than_artificial_tolerance(m_core_solver->get_cost())) {
+            this->m_status = FEASIBLE;
+        } else {
+            this->m_status = UNBOUNDED;
+        }
+        break;
+    case DUAL_UNBOUNDED:
+        lean_unreachable();
+    case ITERATIONS_EXHAUSTED:
+        this->m_status = ITERATIONS_EXHAUSTED;
+        break;
+    case TIME_EXHAUSTED:
+        this->m_status = TIME_EXHAUSTED;
+        break;
+    case FLOATING_POINT_ERROR:
+        this->m_status = FLOATING_POINT_ERROR;
+        break;
+    default:
+        lean_unreachable();
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fix_logical_for_stage2(unsigned j) {
+    lean_assert(j >= this->number_of_core_structurals());
+    switch (m_column_types_of_logicals[j - this->number_of_core_structurals()]) {
+    case column_type::low_bound:
+        m_low_bounds[j] = numeric_traits<T>::zero();
+        m_column_types_of_core_solver[j] = column_type::low_bound;
+        m_can_enter_basis[j] = true;
+        break;
+    case column_type::fixed:
+        this->m_upper_bounds[j] = m_low_bounds[j] = numeric_traits<T>::zero();
+        m_column_types_of_core_solver[j] = column_type::fixed;
+        m_can_enter_basis[j] = false;
+        break;
+    default:
+        lean_unreachable();
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fix_structural_for_stage2(unsigned j) {
+    column_info<T> * ci = this->m_map_from_var_index_to_column_info[this->m_core_solver_columns_to_external_columns[j]];
+    switch (ci->get_column_type()) {
+    case column_type::low_bound:
+        m_low_bounds[j] = numeric_traits<T>::zero();
+        m_column_types_of_core_solver[j] = column_type::low_bound;
+        m_can_enter_basis[j] = true;
+        break;
+    case column_type::fixed:
+    case column_type::upper_bound:
+        lean_unreachable();
+    case column_type::boxed:
+        this->m_upper_bounds[j] = ci->get_adjusted_upper_bound() / this->m_column_scale[j];
+        m_low_bounds[j] = numeric_traits<T>::zero();
+        m_column_types_of_core_solver[j] = column_type::boxed;
+        m_can_enter_basis[j] = true;
+        break;
+    case column_type::free_column:
+        m_can_enter_basis[j] = true;
+        m_column_types_of_core_solver[j] = column_type::free_column;
+        break;
+    default:
+        lean_unreachable();
+    }
+    //    T cost_was = this->m_costs[j];
+    this->set_scaled_cost(j);
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::unmark_boxed_and_fixed_columns_and_fix_structural_costs() {
+    unsigned j = this->m_A->column_count();
+    while (j-- > this->number_of_core_structurals()) {
+        fix_logical_for_stage2(j);
+    }
+    j = this->number_of_core_structurals();
+    while (j--) {
+        fix_structural_for_stage2(j);
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::restore_right_sides() {
+    unsigned i = this->m_A->row_count();
+    while (i--) {
+        this->m_b[i] = m_b_copy[i];
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::solve_for_stage2() {
+    m_core_solver->restore_non_basis();
+    m_core_solver->solve_yB(m_core_solver->m_y);
+    m_core_solver->fill_reduced_costs_from_m_y_by_rows();
+    m_core_solver->start_with_initial_basis_and_make_it_dual_feasible();
+    m_core_solver->set_status(FEASIBLE);
+    m_core_solver->solve();
+    switch (m_core_solver->get_status()) {
+    case OPTIMAL:
+        this->m_status = OPTIMAL;
+        break;
+    case DUAL_UNBOUNDED:
+        this->m_status = INFEASIBLE;
+        break;
+    case TIME_EXHAUSTED:
+        this->m_status = TIME_EXHAUSTED;
+        break;
+    case FLOATING_POINT_ERROR:
+        this->m_status = FLOATING_POINT_ERROR;
+        break;
+    default:
+        lean_unreachable();
+    }
+    this->m_second_stage_iterations = m_core_solver->total_iterations();
+    this->m_total_iterations = (this->m_first_stage_iterations + this->m_second_stage_iterations);
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fill_x_with_zeros() {
+    unsigned j = this->m_A->column_count();
+    while (j--) {
+        this->m_x[j] = numeric_traits<T>::zero();
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::stage1() {
+    lean_assert(m_core_solver == nullptr);
+    this->m_x.resize(this->m_A->column_count(), numeric_traits<T>::zero());
+    if (this->m_settings.get_message_ostream() != nullptr)
+        this->print_statistics_on_A(*this->m_settings.get_message_ostream());
+    m_core_solver = new lp_dual_core_solver<T, X>(
+                                                  *this->m_A,
+                                                  m_can_enter_basis,
+                                                  this->m_b, // the right side vector
+                                                  this->m_x,
+                                                  this->m_basis,
+                                                  this->m_nbasis,
+                                                  this->m_heading,
+                                                  this->m_costs,
+                                                  this->m_column_types_of_core_solver,
+                                                  this->m_low_bounds,
+                                                  this->m_upper_bounds,
+                                                  this->m_settings,
+                                                  *this);
+    m_core_solver->fill_reduced_costs_from_m_y_by_rows();
+    m_core_solver->start_with_initial_basis_and_make_it_dual_feasible();
+    if (this->m_settings.abs_val_is_smaller_than_artificial_tolerance(m_core_solver->get_cost())) {
+        // skipping stage 1
+        m_core_solver->set_status(OPTIMAL);
+        m_core_solver->set_total_iterations(0);
+    } else {
+        m_core_solver->solve();
+    }
+    decide_on_status_after_stage1();
+    this->m_first_stage_iterations = m_core_solver->total_iterations();
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::stage2() {
+    unmark_boxed_and_fixed_columns_and_fix_structural_costs();
+    restore_right_sides();
+    solve_for_stage2();
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fill_first_stage_solver_fields() {
+    unsigned slack_var = this->number_of_core_structurals();
+    unsigned artificial = this->number_of_core_structurals() + this->m_slacks;
+
+    for (unsigned row = 0; row < this->row_count(); row++) {
+        fill_first_stage_solver_fields_for_row_slack_and_artificial(row, slack_var, artificial);
+    }
+    fill_costs_and_bounds_and_column_types_for_the_first_stage_solver();
+}
+
+template <typename T, typename X> column_type lp_dual_simplex<T, X>::get_column_type(unsigned j) {
+    lean_assert(j < this->m_A->column_count());
+    if (j >= this->number_of_core_structurals()) {
+        return m_column_types_of_logicals[j - this->number_of_core_structurals()];
+    }
+    return this->m_map_from_var_index_to_column_info[this->m_core_solver_columns_to_external_columns[j]]->get_column_type();
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fill_costs_bounds_types_and_can_enter_basis_for_the_first_stage_solver_structural_column(unsigned j) {
+    // see 4.7 in the dissertation of Achim Koberstein
+    lean_assert(this->m_core_solver_columns_to_external_columns.find(j) !=
+                this->m_core_solver_columns_to_external_columns.end());
+
+    T free_bound = T(1e4); // see 4.8
+    unsigned jj = this->m_core_solver_columns_to_external_columns[j];
+    lean_assert(this->m_map_from_var_index_to_column_info.find(jj) != this->m_map_from_var_index_to_column_info.end());
+    column_info<T> * ci = this->m_map_from_var_index_to_column_info[jj];
+    switch (ci->get_column_type()) {
+    case column_type::upper_bound: {
+        std::stringstream s;
+        s << "unexpected bound type " << j << " "
+          << column_type_to_string(get_column_type(j));
+        throw_exception(s.str());
+        break;
+    }
+    case column_type::low_bound: {
+        m_can_enter_basis[j] = true;
+        this->set_scaled_cost(j);
+        this->m_low_bounds[j] = numeric_traits<T>::zero();
+        this->m_upper_bounds[j] =numeric_traits<T>::one();
+        break;
+    }
+    case column_type::free_column: {
+        m_can_enter_basis[j] = true;
+        this->set_scaled_cost(j);
+        this->m_upper_bounds[j] = free_bound;
+        this->m_low_bounds[j] =  -free_bound;
+        break;
+    }
+    case column_type::boxed:
+        m_can_enter_basis[j] = false;
+        this->m_costs[j] = numeric_traits<T>::zero();
+        this->m_upper_bounds[j] = this->m_low_bounds[j] =  numeric_traits<T>::zero(); // is it needed?
+        break;
+    default:
+        lean_unreachable();
+    }
+    m_column_types_of_core_solver[j] = column_type::boxed;
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fill_costs_bounds_types_and_can_enter_basis_for_the_first_stage_solver_logical_column(unsigned j) {
+    this->m_costs[j] = 0;
+    lean_assert(get_column_type(j) != column_type::upper_bound);
+    if ((m_can_enter_basis[j] = (get_column_type(j) == column_type::low_bound))) {
+        m_column_types_of_core_solver[j] = column_type::boxed;
+        this->m_low_bounds[j] = numeric_traits<T>::zero();
+        this->m_upper_bounds[j] = numeric_traits<T>::one();
+    } else {
+        m_column_types_of_core_solver[j] = column_type::fixed;
+        this->m_low_bounds[j] = numeric_traits<T>::zero();
+        this->m_upper_bounds[j] = numeric_traits<T>::zero();
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fill_costs_and_bounds_and_column_types_for_the_first_stage_solver() {
+    unsigned j = this->m_A->column_count();
+    while (j-- > this->number_of_core_structurals()) { // go over logicals here
+        fill_costs_bounds_types_and_can_enter_basis_for_the_first_stage_solver_logical_column(j);
+    }
+    j = this->number_of_core_structurals();
+    while (j--) {
+        fill_costs_bounds_types_and_can_enter_basis_for_the_first_stage_solver_structural_column(j);
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::fill_first_stage_solver_fields_for_row_slack_and_artificial(unsigned row,
+                                                                                                                          unsigned & slack_var,
+                                                                                                                          unsigned & artificial) {
+    lean_assert(row < this->row_count());
+    auto & constraint = this->m_constraints[this->m_core_solver_rows_to_external_rows[row]];
+    // we need to bring the program to the form Ax = b
+    T rs = this->m_b[row];
+    switch (constraint.m_relation) {
+    case Equal: // no slack variable here
+        set_type_for_logical(artificial, column_type::fixed);
+        this->m_basis[row] = artificial;
+        this->m_costs[artificial] = numeric_traits<T>::zero();
+        (*this->m_A)(row, artificial) = numeric_traits<T>::one();
+        artificial++;
+        break;
+
+    case Greater_or_equal:
+        set_type_for_logical(slack_var, column_type::low_bound);
+        (*this->m_A)(row, slack_var) = - numeric_traits<T>::one();
+        if (rs > 0) {
+            // adding one artificial
+            set_type_for_logical(artificial, column_type::fixed);
+            (*this->m_A)(row, artificial) = numeric_traits<T>::one();
+            this->m_basis[row] = artificial;
+            this->m_costs[artificial] = numeric_traits<T>::zero();
+            artificial++;
+        } else {
+            // we can put a slack_var into the basis, and avoid adding an artificial variable
+            this->m_basis[row] = slack_var;
+            this->m_costs[slack_var] = numeric_traits<T>::zero();
+        }
+        slack_var++;
+        break;
+    case Less_or_equal:
+        // introduce a non-negative slack variable
+        set_type_for_logical(slack_var, column_type::low_bound);
+        (*this->m_A)(row, slack_var) = numeric_traits<T>::one();
+        if (rs < 0) {
+            // adding one artificial
+            set_type_for_logical(artificial, column_type::fixed);
+            (*this->m_A)(row, artificial) = - numeric_traits<T>::one();
+            this->m_basis[row] = artificial;
+            this->m_costs[artificial] = numeric_traits<T>::zero();
+            artificial++;
+        } else {
+            // we can put slack_var into the basis, and avoid adding an artificial variable
+            this->m_basis[row] = slack_var;
+            this->m_costs[slack_var] = numeric_traits<T>::zero();
+        }
+        slack_var++;
+        break;
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::augment_matrix_A_and_fill_x_and_allocate_some_fields() {
+    this->count_slacks_and_artificials();
+    this->m_A->add_columns_at_the_end(this->m_slacks + this->m_artificials);
+    unsigned n = this->m_A->column_count();
+    this->m_column_types_of_core_solver.resize(n);
+    m_column_types_of_logicals.resize(this->m_slacks + this->m_artificials);
+    this->m_costs.resize(n);
+    this->m_upper_bounds.resize(n);
+    this->m_low_bounds.resize(n);
+    m_can_enter_basis.resize(n);
+    this->m_basis.resize(this->m_A->row_count());
+}
+
+
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::copy_m_b_aside_and_set_it_to_zeros() {
+    for (unsigned i = 0; i < this->m_b.size(); i++) {
+        m_b_copy.push_back(this->m_b[i]);
+        this->m_b[i] = numeric_traits<T>::zero(); // preparing for the first stage
+    }
+}
+
+template <typename T, typename X> void lp_dual_simplex<T, X>::find_maximal_solution(){
+    if (this->problem_is_empty()) {
+        this->m_status = lp_status::EMPTY;
+        return;
+    }
+
+    this->flip_costs(); // do it for now, todo ( remove the flipping)
+
+    this->cleanup();
+    if (this->m_status == INFEASIBLE) {
+        return;
+    }
+    this->fill_matrix_A_and_init_right_side();
+    this->fill_m_b();
+    this->scale();
+    augment_matrix_A_and_fill_x_and_allocate_some_fields();
+    fill_first_stage_solver_fields();
+    copy_m_b_aside_and_set_it_to_zeros();
+    stage1();
+    if (this->m_status == FEASIBLE) {
+        stage2();
+    }
+}
+
+
+template <typename T, typename X> T lp_dual_simplex<T, X>::get_current_cost() const {
+    T ret = numeric_traits<T>::zero();
+    for (auto it : this->m_map_from_var_index_to_column_info) {
+        ret += this->get_column_cost_value(it.first, it.second);
+    }
+    return -ret; // we flip costs for now
+}
+}

src/util/lp/lp_dual_simplex_instances.cpp

@@ -0,0 +1,9 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include "util/lp/lp_dual_simplex.hpp"
+template lean::mpq lean::lp_dual_simplex<lean::mpq, lean::mpq>::get_current_cost() const;
+template void lean::lp_dual_simplex<lean::mpq, lean::mpq>::find_maximal_solution();
+template double lean::lp_dual_simplex<double, double>::get_current_cost() const;
+template void lean::lp_dual_simplex<double, double>::find_maximal_solution();

src/util/lp/lp_params.pyg

@@ -0,0 +1,13 @@
+def_module_params('lp', 
+                  export=True,
+                  params=(
+                  ('rep_freq', UINT, 0, 'the report frequency, in how many iterations print the cost and other info '),
+                   ('min', BOOL, False, 'minimize cost'),
+                   ('presolve_with_dbl', BOOL, True, 'presolve with double'),
+                   ('print_stats', BOOL, False, 'print statistic'),
+                   ('simplex_strategy', UINT, 0, 'simplex strategy for the solver'),
+                   ('bprop_on_pivoted_rows', BOOL, True, 'propagate bounds on rows changed by the pivot operation')
+                          ))           
+
+
+    

src/util/lp/lp_primal_core_solver.h

@@ -0,0 +1,986 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include <list>
+#include <limits>
+#include <unordered_map>
+#include <sstream>
+#include <string>
+#include "util/vector.h"
+#include <set>
+#include <math.h>
+#include <cstdlib>
+#include <algorithm>
+#include "util/lp/lu.h"
+#include "util/lp/lp_solver.h"
+#include "util/lp/static_matrix.h"
+#include "util/lp/core_solver_pretty_printer.h"
+#include "util/lp/lp_core_solver_base.h"
+#include "util/lp/breakpoint.h"
+#include "util/lp/binary_heap_priority_queue.h"
+#include "util/lp/int_set.h"
+#include "util/lp/iterator_on_row.h"
+namespace lean {
+
+// This core solver solves (Ax=b, low_bound_values \leq x \leq upper_bound_values, maximize costs*x )
+// The right side b is given implicitly by x and the basis
+template <typename T, typename X>
+class lp_primal_core_solver:public lp_core_solver_base<T, X> {
+public:
+    // m_sign_of_entering is set to 1 if the entering variable needs
+    // to grow and is set to -1  otherwise
+    unsigned m_column_norm_update_counter;
+    T m_enter_price_eps;
+    int m_sign_of_entering_delta;
+    vector<breakpoint<X>> m_breakpoints;
+    binary_heap_priority_queue<X> m_breakpoint_indices_queue;
+    indexed_vector<T> m_beta; // see Swietanowski working vector beta for column norms
+    T m_epsilon_of_reduced_cost = T(1)/T(10000000);
+    vector<T> m_costs_backup;
+    T m_converted_harris_eps;
+    unsigned m_inf_row_index_for_tableau;
+    bool m_bland_mode_tableau;
+    int_set m_left_basis_tableau;
+    unsigned m_bland_mode_threshold = 1000;
+    unsigned m_left_basis_repeated;
+    vector<unsigned> m_leaving_candidates;
+    //    T m_converted_harris_eps = convert_struct<T, double>::convert(this->m_settings.harris_feasibility_tolerance);
+    std::list<unsigned> m_non_basis_list;
+    void sort_non_basis();
+    void sort_non_basis_rational();
+    int choose_entering_column(unsigned number_of_benefitial_columns_to_go_over);
+    int choose_entering_column_tableau();
+    int choose_entering_column_presize(unsigned number_of_benefitial_columns_to_go_over);
+    int find_leaving_and_t_with_breakpoints(unsigned entering, X & t);
+    // int find_inf_row() {
+    //     // mimicing CLP : todo : use a heap
+    //     int j = -1;
+    //     for (unsigned k : this->m_inf_set.m_index) {
+    //         if (k < static_cast<unsigned>(j))
+    //             j = static_cast<int>(k);
+    //     }
+    //     if (j == -1)
+    //         return -1;
+    //     return this->m_basis_heading[j];
+    //     #if 0 
+    //     vector<int> choices;
+    //     unsigned len = 100000000; 
+    //     for (unsigned j : this->m_inf_set.m_index) {
+    //         int i = this->m_basis_heading[j];
+    //         lean_assert(i >= 0);
+    //         unsigned row_len = this->m_A.m_rows[i].size();
+    //         if (row_len < len) {
+    //             choices.clear();
+    //             choices.push_back(i);
+    //             len = row_len;
+    //             if (my_random() % 10) break;
+    //         } else if (row_len == len) {
+    //             choices.push_back(i);
+    //             if (my_random() % 10) break;
+    //         }
+    //     }
+
+    //     if (choices.size() == 0)
+    //         return -1;
+
+    //     if (choices.size() == 1)
+    //         return choices[0];
+        
+    //     unsigned k = my_random() % choices.size();
+    //     return choices[k];
+    //     #endif
+    // }
+
+
+    bool column_is_benefitial_for_entering_basis_on_sign_row_strategy(unsigned j, int sign) const {
+        // sign = 1 means the x of the basis column of the row has to grow to become feasible, when the coeff before j is neg, or x - has to diminish when the coeff is pos
+        // we have xbj = -aj * xj
+        lean_assert(this->m_basis_heading[j] < 0);
+        lean_assert(this->column_is_feasible(j));
+        switch (this->m_column_types[j]) {
+        case column_type::free_column: return true;
+        case column_type::fixed: return false;
+        case column_type::low_bound:
+            if (sign < 0)
+                return true;
+            return !this->x_is_at_low_bound(j);
+        case column_type::upper_bound:
+            if (sign > 0)
+                return true;
+            return !this->x_is_at_upper_bound(j);
+        case column_type::boxed:
+            if (sign < 0)
+                return !this->x_is_at_low_bound(j);
+            return !this->x_is_at_upper_bound(j);
+        }
+
+        lean_assert(false); // cannot be here
+        return false;
+    }
+    
+
+    bool needs_to_grow(unsigned bj) const {
+        lean_assert(!this->column_is_feasible(bj));
+        switch(this->m_column_types[bj]) {
+        case column_type::free_column:
+            return false;
+        case column_type::fixed: 
+        case column_type::low_bound:
+        case column_type::boxed:
+            return this-> x_below_low_bound(bj);
+        default:
+            return false;
+        }
+        lean_assert(false); // unreachable
+        return false;
+    }
+
+    int inf_sign_of_column(unsigned bj) const {
+        lean_assert(!this->column_is_feasible(bj));
+        switch(this->m_column_types[bj]) {
+        case column_type::free_column:
+            return 0;
+        case column_type::low_bound:
+            return 1;
+        case column_type::fixed: 
+        case column_type::boxed:            
+            return this->x_above_upper_bound(bj)? -1: 1;
+        default:
+            return -1;
+        }
+        lean_assert(false); // unreachable
+        return 0;
+        
+    }
+    
+
+    bool monoid_can_decrease(const row_cell<T> & rc) const {
+        unsigned j = rc.m_j;
+        lean_assert(this->column_is_feasible(j));
+        switch (this->m_column_types[j]) {
+        case column_type::free_column:
+            return true;
+        case column_type::fixed:
+            return false;
+        case column_type::low_bound:
+            if (is_pos(rc.get_val())) {
+                return this->x_above_low_bound(j);
+            }
+
+            return true;
+        case column_type::upper_bound:
+            if (is_pos(rc.get_val())) {
+                return true;
+            }
+
+            return this->x_below_upper_bound(j);
+        case column_type::boxed:
+            if (is_pos(rc.get_val())) {
+                return this->x_above_low_bound(j);
+            }
+
+            return this->x_below_upper_bound(j);
+        default:
+            return false;
+        }
+        lean_assert(false); // unreachable
+        return false;
+    }
+
+    bool monoid_can_increase(const row_cell<T> & rc) const {
+        unsigned j = rc.m_j;
+        lean_assert(this->column_is_feasible(j));
+        switch (this->m_column_types[j]) {
+        case column_type::free_column:
+            return true;
+        case column_type::fixed:
+            return false;
+        case column_type::low_bound:
+            if (is_neg(rc.get_val())) {
+                return this->x_above_low_bound(j);
+            }
+
+            return true;
+        case column_type::upper_bound:
+            if (is_neg(rc.get_val())) {
+                return true;
+            }
+
+            return this->x_below_upper_bound(j);
+        case column_type::boxed:
+            if (is_neg(rc.get_val())) {
+                return this->x_above_low_bound(j);
+            }
+
+            return this->x_below_upper_bound(j);
+        default:
+            return false;
+        }
+        lean_assert(false); // unreachable
+        return false;
+    }
+
+    unsigned get_number_of_basic_vars_that_might_become_inf(unsigned j) const { // consider looking at the signs here: todo
+        unsigned r = 0;
+        for (auto & cc : this->m_A.m_columns[j]) {
+            unsigned k = this->m_basis[cc.m_i];
+            if (this->m_column_types[k] != column_type::free_column)
+                r++;
+        }
+        return r;
+    }
+
+    
+    int find_beneficial_column_in_row_tableau_rows_bland_mode(int i, T & a_ent) {
+        int j = -1;
+        unsigned bj = this->m_basis[i];
+        bool bj_needs_to_grow = needs_to_grow(bj);
+        for (const row_cell<T>& rc : this->m_A.m_rows[i]) {
+            if (rc.m_j == bj)
+                continue;
+            if (bj_needs_to_grow) {
+                if (!monoid_can_decrease(rc))
+                    continue;
+            } else {
+                if (!monoid_can_increase(rc))
+                    continue;
+            }
+            if (rc.m_j < static_cast<unsigned>(j) ) {
+                j = rc.m_j;
+                a_ent = rc.m_value;
+            }
+        }
+        if (j == -1) {
+            m_inf_row_index_for_tableau = i;
+        }
+            
+        return j;
+    }
+    
+    int find_beneficial_column_in_row_tableau_rows(int i, T & a_ent) {
+        if (m_bland_mode_tableau)
+            return find_beneficial_column_in_row_tableau_rows_bland_mode(i, a_ent);
+        // a short row produces short infeasibility explanation and benefits at least one pivot operation
+        vector<const row_cell<T>*> choices;
+        unsigned num_of_non_free_basics = 1000000;
+        unsigned len = 100000000;
+        unsigned bj = this->m_basis[i];
+        bool bj_needs_to_grow = needs_to_grow(bj);
+        for (const row_cell<T>& rc : this->m_A.m_rows[i]) {
+            unsigned j = rc.m_j;
+            if (j == bj)
+                continue;
+            if (bj_needs_to_grow) {
+                if (!monoid_can_decrease(rc))
+                    continue;
+            } else {
+                if (!monoid_can_increase(rc))
+                    continue;
+            }
+            unsigned damage = get_number_of_basic_vars_that_might_become_inf(j);
+            if (damage < num_of_non_free_basics) {
+                num_of_non_free_basics = damage;
+                len = this->m_A.m_columns[j].size();
+                choices.clear();
+                choices.push_back(&rc);
+            } else if (damage == num_of_non_free_basics &&
+                       this->m_A.m_columns[j].size() <= len && (my_random() % 2)) {
+                choices.push_back(&rc);
+                len = this->m_A.m_columns[j].size();
+            }
+        }
+        
+
+        if (choices.size() == 0) {
+            m_inf_row_index_for_tableau = i;
+            return -1;
+        }
+        const row_cell<T>* rc = choices.size() == 1? choices[0] :
+            choices[my_random() % choices.size()];
+
+        a_ent = rc->m_value;
+        return rc->m_j;
+    }
+    static X positive_infinity() {
+        return convert_struct<X, unsigned>::convert(std::numeric_limits<unsigned>::max());
+    }
+
+    bool get_harris_theta(X & theta);
+
+    void restore_harris_eps() { m_converted_harris_eps = convert_struct<T, double>::convert(this->m_settings.harris_feasibility_tolerance); }
+    void zero_harris_eps() { m_converted_harris_eps = zero_of_type<T>(); }
+    int find_leaving_on_harris_theta(X const & harris_theta, X & t);
+    bool try_jump_to_another_bound_on_entering(unsigned entering, const X & theta, X & t, bool & unlimited);
+    bool try_jump_to_another_bound_on_entering_unlimited(unsigned entering, X & t);
+    int find_leaving_and_t(unsigned entering, X & t);
+    int find_leaving_and_t_precise(unsigned entering, X & t);
+    int find_leaving_and_t_tableau(unsigned entering, X & t);
+ 
+    void limit_theta(const X & lim, X & theta, bool & unlimited) {
+        if (unlimited) {
+            theta = lim;
+            unlimited = false;
+        } else {
+            theta = std::min(lim, theta);
+        }
+    }
+
+    void limit_theta_on_basis_column_for_inf_case_m_neg_upper_bound(unsigned j, const T & m, X & theta, bool & unlimited) {
+        lean_assert(m < 0 && this->m_column_types[j] == column_type::upper_bound);
+        limit_inf_on_upper_bound_m_neg(m, this->m_x[j], this->m_upper_bounds[j], theta, unlimited);
+    }
+
+
+    void limit_theta_on_basis_column_for_inf_case_m_neg_low_bound(unsigned j, const T & m, X & theta, bool & unlimited) {
+        lean_assert(m < 0 && this->m_column_types[j] == column_type::low_bound);
+        limit_inf_on_bound_m_neg(m, this->m_x[j], this->m_low_bounds[j], theta, unlimited);
+    }
+
+
+    void limit_theta_on_basis_column_for_inf_case_m_pos_low_bound(unsigned j, const T & m, X & theta, bool & unlimited) {
+        lean_assert(m > 0 && this->m_column_types[j] == column_type::low_bound);
+        limit_inf_on_low_bound_m_pos(m, this->m_x[j], this->m_low_bounds[j], theta, unlimited);
+    }
+
+    void limit_theta_on_basis_column_for_inf_case_m_pos_upper_bound(unsigned j, const T & m, X & theta, bool & unlimited) {
+        lean_assert(m > 0 && this->m_column_types[j] == column_type::upper_bound);
+        limit_inf_on_bound_m_pos(m, this->m_x[j], this->m_upper_bounds[j], theta, unlimited);
+    };
+
+    X harris_eps_for_bound(const X & bound) const { return ( convert_struct<X, int>::convert(1) +  abs(bound)/10) * m_converted_harris_eps/3;
+    }
+
+    void get_bound_on_variable_and_update_leaving_precisely(unsigned j, vector<unsigned> & leavings, T m, X & t, T & abs_of_d_of_leaving);
+
+    vector<T> m_low_bounds_dummy; // needed for the base class only
+
+    X get_max_bound(vector<X> & b);
+
+#ifdef LEAN_DEBUG
+    void check_Ax_equal_b();
+    void check_the_bounds();
+    void check_bound(unsigned i);
+    void check_correctness();
+#endif
+
+    // from page 183 of Istvan Maros's book
+    // the basis structures have not changed yet
+    void update_reduced_costs_from_pivot_row(unsigned entering, unsigned leaving);
+
+    // return 0 if the reduced cost at entering is close enough to the refreshed
+    // 1 if it is way off, and 2 if it is unprofitable
+    int refresh_reduced_cost_at_entering_and_check_that_it_is_off(unsigned entering);
+
+    void backup_and_normalize_costs();
+
+    void init_run();
+
+    void calc_working_vector_beta_for_column_norms();
+
+    void advance_on_entering_and_leaving(int entering, int leaving, X & t);
+    void advance_on_entering_and_leaving_tableau(int entering, int leaving, X & t);
+    void advance_on_entering_equal_leaving(int entering, X & t);
+    void advance_on_entering_equal_leaving_tableau(int entering, X & t);
+
+    bool need_to_switch_costs() const {
+        if (this->m_settings.simplex_strategy() == simplex_strategy_enum::tableau_rows)
+            return false;
+        //        lean_assert(calc_current_x_is_feasible() == current_x_is_feasible());
+        return this->current_x_is_feasible() == this->m_using_infeas_costs;
+    }
+
+
+    void advance_on_entering(int entering);
+    void advance_on_entering_tableau(int entering);
+    void advance_on_entering_precise(int entering);
+    void push_forward_offset_in_non_basis(unsigned & offset_in_nb);
+
+    unsigned get_number_of_non_basic_column_to_try_for_enter();
+
+    void print_column_norms(std::ostream & out);
+
+    // returns the number of iterations
+    unsigned solve();
+
+    lu<T, X> * factorization() {return this->m_factorization;}
+
+    void delete_factorization();
+
+    // according to Swietanowski, " A new steepest edge approximation for the simplex method for linear programming"
+    void init_column_norms();
+
+    T calculate_column_norm_exactly(unsigned j);
+
+    void update_or_init_column_norms(unsigned entering, unsigned leaving);
+
+    // following Swietanowski - A new steepest ...
+    void update_column_norms(unsigned entering, unsigned leaving);
+
+    T calculate_norm_of_entering_exactly();
+
+    void find_feasible_solution();
+
+    bool is_tiny() const {return this->m_m < 10 && this->m_n < 20;}
+
+    void one_iteration();
+    void one_iteration_tableau();
+
+    void advance_on_entering_and_leaving_tableau_rows(int entering, int leaving, const X &theta ) {
+        this->update_basis_and_x_tableau(entering, leaving, theta);
+        this->update_column_in_inf_set(entering);
+    }
+
+
+    int find_leaving_tableau_rows(X & new_val_for_leaving) {
+        int j = -1;
+        for (unsigned k : this->m_inf_set.m_index) {
+            if (k < static_cast<unsigned>(j))
+                j = static_cast<int>(k);
+        }
+        if (j == -1)
+            return -1;
+
+        lean_assert(!this->column_is_feasible(j));
+        switch (this->m_column_types[j]) {
+        case column_type::fixed:
+        case column_type::upper_bound:
+            new_val_for_leaving = this->m_upper_bounds[j];
+            break;
+        case column_type::low_bound:
+            new_val_for_leaving = this->m_low_bounds[j];
+            break;
+        case column_type::boxed:
+            if (this->x_above_upper_bound(j))
+                new_val_for_leaving = this->m_upper_bounds[j];
+            else
+                new_val_for_leaving = this->m_low_bounds[j];
+            break;
+        default:
+            lean_assert(false);
+        }
+        return j;
+    }
+    
+    void one_iteration_tableau_rows() {
+        X new_val_for_leaving;
+        int leaving = find_leaving_tableau_rows(new_val_for_leaving);
+        if (leaving == -1) {
+            this->set_status(OPTIMAL);
+            return;
+        }
+
+        if (!m_bland_mode_tableau) {
+            if (m_left_basis_tableau.contains(leaving)) {
+                if (++m_left_basis_repeated > m_bland_mode_threshold) {
+                    m_bland_mode_tableau = true;
+                }
+            } else {
+                m_left_basis_tableau.insert(leaving);
+            }
+        }
+        T a_ent;
+        int entering = find_beneficial_column_in_row_tableau_rows(this->m_basis_heading[leaving], a_ent);
+        if (entering == -1) {
+            this->set_status(INFEASIBLE);
+            return;
+        }
+        X theta = (this->m_x[leaving] - new_val_for_leaving) / a_ent;
+        advance_on_entering_and_leaving_tableau_rows(entering, leaving, theta );
+        lean_assert(this->m_x[leaving] == new_val_for_leaving);
+        if (this->current_x_is_feasible())
+            this->set_status(OPTIMAL);
+    }
+
+    void fill_breakpoints_array(unsigned entering);
+
+    void try_add_breakpoint_in_row(unsigned i);
+
+    void clear_breakpoints();
+
+    void change_slope_on_breakpoint(unsigned entering, breakpoint<X> * b, T & slope_at_entering);
+    void advance_on_sorted_breakpoints(unsigned entering);
+
+    void update_basis_and_x_with_comparison(unsigned entering, unsigned leaving, X delta);
+
+    void decide_on_status_when_cannot_find_entering() {
+        lean_assert(!need_to_switch_costs());
+        this->set_status(this->current_x_is_feasible()? OPTIMAL: INFEASIBLE);
+    }
+
+    // void limit_theta_on_basis_column_for_feas_case_m_neg(unsigned j, const T & m, X & theta) {
+    //     lean_assert(m < 0);
+    //     lean_assert(this->m_column_type[j] == low_bound || this->m_column_type[j] == boxed);
+    //     const X & eps = harris_eps_for_bound(this->m_low_bounds[j]);
+    //     if (this->above_bound(this->m_x[j], this->m_low_bounds[j])) {
+    //         theta = std::min((this->m_low_bounds[j] -this->m_x[j] - eps) / m, theta);
+    //         if (theta < zero_of_type<X>()) theta = zero_of_type<X>();
+    //     }
+    // }
+
+    void limit_theta_on_basis_column_for_feas_case_m_neg_no_check(unsigned j, const T & m, X & theta, bool & unlimited) {
+        lean_assert(m < 0);
+        const X& eps = harris_eps_for_bound(this->m_low_bounds[j]);
+        limit_theta((this->m_low_bounds[j] - this->m_x[j] - eps) / m, theta, unlimited);
+        if (theta < zero_of_type<X>()) theta = zero_of_type<X>();
+    }
+
+    bool limit_inf_on_bound_m_neg(const T & m, const X & x, const X & bound, X & theta, bool & unlimited) {
+        // x gets smaller
+        lean_assert(m < 0);
+        if (numeric_traits<T>::precise()) {
+            if (this->below_bound(x, bound)) return false;
+            if (this->above_bound(x, bound)) {
+                limit_theta((bound - x) / m, theta, unlimited);
+            } else {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        } else {
+            const X& eps = harris_eps_for_bound(bound);
+            if (this->below_bound(x, bound)) return false;
+            if (this->above_bound(x, bound)) {
+                limit_theta((bound - x - eps) / m, theta, unlimited);
+            } else {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        }
+        return true;
+    }
+
+    bool limit_inf_on_bound_m_pos(const T & m, const X & x, const X & bound, X & theta, bool & unlimited) {
+        // x gets larger
+        lean_assert(m > 0);
+        if (numeric_traits<T>::precise()) {
+            if (this->above_bound(x, bound)) return false;
+            if (this->below_bound(x, bound)) {
+                limit_theta((bound - x) / m, theta, unlimited);
+            } else {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        } else {
+            const X& eps = harris_eps_for_bound(bound);
+            if (this->above_bound(x, bound)) return false;
+            if (this->below_bound(x, bound)) {
+                limit_theta((bound - x + eps) / m, theta, unlimited);
+            } else {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        }
+        return true;
+    }
+
+    void limit_inf_on_low_bound_m_pos(const T & m, const X & x, const X & bound, X & theta, bool & unlimited) {
+        if (numeric_traits<T>::precise()) {
+            // x gets larger
+            lean_assert(m > 0);
+            if (this->below_bound(x, bound)) {
+                limit_theta((bound - x) / m, theta, unlimited);
+            }
+        }
+        else {
+            // x gets larger
+            lean_assert(m > 0);
+            const X& eps = harris_eps_for_bound(bound);
+            if (this->below_bound(x, bound)) {
+                limit_theta((bound - x + eps) / m, theta, unlimited);
+            }
+        }
+    }
+
+    void limit_inf_on_upper_bound_m_neg(const T & m, const X & x, const X & bound, X & theta, bool & unlimited) {
+        // x gets smaller
+        lean_assert(m < 0);
+        const X& eps = harris_eps_for_bound(bound);
+        if (this->above_bound(x, bound)) {
+            limit_theta((bound - x - eps) / m, theta, unlimited);
+        }
+    }
+
+    void limit_theta_on_basis_column_for_inf_case_m_pos_boxed(unsigned j, const T & m, X & theta, bool & unlimited) {
+        //        lean_assert(m > 0 && this->m_column_type[j] == column_type::boxed);
+        const X & x = this->m_x[j];
+        const X & lbound = this->m_low_bounds[j];
+
+        if (this->below_bound(x, lbound)) {
+            const X& eps = harris_eps_for_bound(this->m_upper_bounds[j]);
+            limit_theta((lbound - x + eps) / m, theta, unlimited);
+        } else {
+            const X & ubound = this->m_upper_bounds[j];
+            if (this->below_bound(x, ubound)){
+                const X& eps = harris_eps_for_bound(ubound);
+                limit_theta((ubound - x + eps) / m, theta, unlimited);
+            } else if (!this->above_bound(x, ubound)) {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        }
+    }
+
+    void limit_theta_on_basis_column_for_inf_case_m_neg_boxed(unsigned j, const T & m, X & theta, bool & unlimited) {
+        //  lean_assert(m < 0 && this->m_column_type[j] == column_type::boxed);
+        const X & x = this->m_x[j];
+        const X & ubound = this->m_upper_bounds[j];
+        if (this->above_bound(x, ubound)) {
+            const X& eps = harris_eps_for_bound(ubound);
+            limit_theta((ubound - x - eps) / m, theta, unlimited);
+        } else {
+            const X & lbound = this->m_low_bounds[j];
+            if (this->above_bound(x, lbound)){
+                const X& eps = harris_eps_for_bound(lbound);
+                limit_theta((lbound - x - eps) / m, theta, unlimited);
+            } else if (!this->below_bound(x, lbound)) {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        }
+    }
+    void limit_theta_on_basis_column_for_feas_case_m_pos(unsigned j, const T & m, X & theta, bool & unlimited) {
+        lean_assert(m > 0);
+        const T& eps = harris_eps_for_bound(this->m_upper_bounds[j]);
+        if (this->below_bound(this->m_x[j], this->m_upper_bounds[j])) {
+            limit_theta((this->m_upper_bounds[j] - this->m_x[j] + eps) / m, theta, unlimited);
+            if (theta < zero_of_type<X>()) {
+                theta = zero_of_type<X>();
+                unlimited = false;
+            }
+        }
+    }
+
+    void limit_theta_on_basis_column_for_feas_case_m_pos_no_check(unsigned j, const T & m, X & theta, bool & unlimited ) {
+        lean_assert(m > 0);
+        const X& eps = harris_eps_for_bound(this->m_upper_bounds[j]);
+        limit_theta( (this->m_upper_bounds[j] - this->m_x[j] + eps) / m, theta, unlimited);
+        if (theta < zero_of_type<X>()) {
+            theta = zero_of_type<X>();
+        }
+    }
+
+    // j is a basic column or the entering, in any case x[j] has to stay feasible.
+    // m is the multiplier. updating t in a way that holds the following
+    // x[j] + t * m >=  this->m_low_bounds[j]- harris_feasibility_tolerance ( if m < 0 )
+    // or
+    // x[j] + t * m <= this->m_upper_bounds[j] + harris_feasibility_tolerance ( if m > 0)
+    void limit_theta_on_basis_column(unsigned j, T m, X & theta, bool & unlimited) {
+        switch (this->m_column_types[j]) {
+        case column_type::free_column: break;
+        case column_type::upper_bound:
+            if (this->current_x_is_feasible()) {
+                if (m > 0)
+                    limit_theta_on_basis_column_for_feas_case_m_pos_no_check(j, m, theta, unlimited);
+            } else { // inside of feasibility_loop
+                if (m > 0)
+                    limit_theta_on_basis_column_for_inf_case_m_pos_upper_bound(j, m, theta, unlimited);
+                else
+                    limit_theta_on_basis_column_for_inf_case_m_neg_upper_bound(j, m, theta, unlimited);
+            }
+            break;
+        case column_type::low_bound:
+            if (this->current_x_is_feasible()) {
+                if (m < 0)
+                    limit_theta_on_basis_column_for_feas_case_m_neg_no_check(j, m, theta, unlimited);
+            } else {
+                if (m < 0)
+                    limit_theta_on_basis_column_for_inf_case_m_neg_low_bound(j, m, theta, unlimited);
+                else
+                    limit_theta_on_basis_column_for_inf_case_m_pos_low_bound(j, m, theta, unlimited);
+            }
+            break;
+            // case fixed:
+            //     if (get_this->current_x_is_feasible()) {
+            //         theta = zero_of_type<X>();
+            //         break;
+            //     }
+            //     if (m < 0)
+            //         limit_theta_on_basis_column_for_inf_case_m_neg_fixed(j, m, theta);
+            //     else
+            //         limit_theta_on_basis_column_for_inf_case_m_pos_fixed(j, m, theta);
+            //     break;
+        case column_type::fixed:
+        case column_type::boxed:
+            if (this->current_x_is_feasible()) {
+                if (m > 0) {
+                    limit_theta_on_basis_column_for_feas_case_m_pos_no_check(j, m, theta, unlimited);
+                } else {
+                    limit_theta_on_basis_column_for_feas_case_m_neg_no_check(j, m, theta, unlimited);
+                }
+            } else {
+                if (m > 0) {
+                    limit_theta_on_basis_column_for_inf_case_m_pos_boxed(j, m, theta, unlimited);
+                } else {
+                    limit_theta_on_basis_column_for_inf_case_m_neg_boxed(j, m, theta, unlimited);
+                }
+            }
+
+            break;
+        default:
+            lean_unreachable();
+        }
+        if (!unlimited && theta < zero_of_type<X>()) {
+            theta = zero_of_type<X>();
+        }
+    }
+
+    
+    bool column_is_benefitial_for_entering_basis(unsigned j) const;
+    bool column_is_benefitial_for_entering_basis_precise(unsigned j) const;
+
+    bool column_is_benefitial_for_entering_on_breakpoints(unsigned j) const;
+
+
+    bool can_enter_basis(unsigned j);
+    bool done();
+    void init_infeasibility_costs();
+    
+    void init_infeasibility_cost_for_column(unsigned j);
+    T get_infeasibility_cost_for_column(unsigned j) const;
+    void init_infeasibility_costs_for_changed_basis_only();
+
+    void print_column(unsigned j, std::ostream & out);
+    void add_breakpoint(unsigned j, X delta, breakpoint_type type);
+
+    // j is the basic column, x is the value at x[j]
+    // d is the coefficient before m_entering in the row with j as the basis column
+    void try_add_breakpoint(unsigned j, const X & x, const T & d, breakpoint_type break_type, const X & break_value);
+    template <typename L>
+    bool same_sign_with_entering_delta(const L & a) {
+        return (a > zero_of_type<L>() && m_sign_of_entering_delta > 0) || (a < zero_of_type<L>() && m_sign_of_entering_delta < 0);
+    }
+
+    void init_reduced_costs();
+
+    bool low_bounds_are_set() const { return true; }
+
+    int advance_on_sorted_breakpoints(unsigned entering, X & t);
+    
+    std::string break_type_to_string(breakpoint_type type);
+
+    void print_breakpoint(const breakpoint<X> * b, std::ostream & out);
+
+    void print_bound_info_and_x(unsigned j, std::ostream & out);
+
+    void init_infeasibility_after_update_x_if_inf(unsigned leaving) {
+        if (this->m_using_infeas_costs) {
+            init_infeasibility_costs_for_changed_basis_only();
+            this->m_costs[leaving] = zero_of_type<T>();
+            this->m_inf_set.erase(leaving);
+        } 
+    }
+    
+    void init_inf_set() {
+        this->m_inf_set.clear();
+        for (unsigned j = 0; j < this->m_n(); j++) {
+            if (this->m_basis_heading[j] < 0)
+                continue;
+            if (!this->column_is_feasible(j))
+                this->m_inf_set.insert(j);
+        }
+    }
+
+    int get_column_out_of_bounds_delta_sign(unsigned j) {
+        switch (this->m_column_types[j]) {
+        case column_type::fixed:
+        case column_type::boxed:
+            if (this->x_below_low_bound(j))
+                return -1;
+            if (this->x_above_upper_bound(j))
+                return 1;
+            break;
+        case column_type::low_bound:
+            if (this->x_below_low_bound(j))
+                return -1;
+            break;
+        case column_type::upper_bound:
+            if (this->x_above_upper_bound(j))
+                return 1;
+            break;
+        case column_type::free_column:
+            return 0;
+        default:
+            lean_assert(false);
+        }
+        return 0;
+    }
+
+    void init_column_row_non_zeroes() {
+        this->m_columns_nz.resize(this->m_A.column_count());
+        this->m_rows_nz.resize(this->m_A.row_count());
+        for (unsigned i = 0; i < this->m_A.column_count(); i++) {
+            if (this->m_columns_nz[i] == 0)
+                this->m_columns_nz[i] = this->m_A.m_columns[i].size();
+        }
+        for (unsigned i = 0; i < this->m_A.row_count(); i++) {
+         if (this->m_rows_nz[i] == 0)
+            this->m_rows_nz[i] = this->m_A.m_rows[i].size();
+        }
+    }
+    
+
+    int x_at_bound_sign(unsigned j) {
+        switch (this->m_column_types[j]) {
+        case column_type::fixed:
+            return 0;
+        case column_type::boxed:
+            if (this->x_is_at_low_bound(j))
+                return 1;
+            return -1;
+            break;
+        case column_type::low_bound:
+            return 1;
+            break;
+        case column_type::upper_bound:
+            return -1;
+            break;
+        default:
+            lean_assert(false);
+        }
+        return 0;
+
+    }
+
+    unsigned solve_with_tableau();
+
+    bool basis_column_is_set_correctly(unsigned j) const {
+        return this->m_A.m_columns[j].size() == 1;
+            
+    }
+    
+    bool basis_columns_are_set_correctly() const {
+        for (unsigned j : this->m_basis)
+            if(!basis_column_is_set_correctly(j))
+                return false;
+        return true;
+    }
+
+    void init_run_tableau();
+    void update_x_tableau(unsigned entering, const X & delta);
+    void update_inf_cost_for_column_tableau(unsigned j);
+
+// the delta is between the old and the new cost (old - new)
+    void update_reduced_cost_for_basic_column_cost_change(const T & delta, unsigned j) {
+        lean_assert(this->m_basis_heading[j] >= 0);
+        unsigned i = static_cast<unsigned>(this->m_basis_heading[j]);
+        for (const row_cell<T> & rc : this->m_A.m_rows[i]) {
+            unsigned k = rc.m_j;
+            if (k == j)
+                continue;
+            this->m_d[k] += delta * rc.get_val();
+        }
+    }
+    
+    bool update_basis_and_x_tableau(int entering, int leaving, X const & tt);
+    void init_reduced_costs_tableau();
+    void init_tableau_rows() {
+        m_bland_mode_tableau = false;
+        m_left_basis_tableau.clear();
+        m_left_basis_tableau.resize(this->m_A.column_count());
+        m_left_basis_repeated = 0;
+    }
+// stage1 constructor
+    lp_primal_core_solver(static_matrix<T, X> & A,
+                          vector<X> & b, // the right side vector
+                          vector<X> & x, // the number of elements in x needs to be at least as large as the number of columns in A
+                          vector<unsigned> & basis,
+                          vector<unsigned> & nbasis,
+                          vector<int> & heading,
+                          vector<T> & costs,
+                          const vector<column_type> & column_type_array,
+                          const vector<X> & low_bound_values,
+                          const vector<X> & upper_bound_values,
+                          lp_settings & settings,
+                          const column_namer& column_names):
+        lp_core_solver_base<T, X>(A, b,
+                                  basis,
+                                  nbasis,
+                                  heading,
+                                  x,
+                                  costs,
+                                  settings,
+                                  column_names,
+                                  column_type_array,
+                                  low_bound_values,
+                                  upper_bound_values),
+        m_beta(A.row_count()) {
+
+        if (!(numeric_traits<T>::precise())) {
+            m_converted_harris_eps = convert_struct<T, double>::convert(this->m_settings.harris_feasibility_tolerance);
+        } else {
+            m_converted_harris_eps = zero_of_type<T>();
+        }
+        this->set_status(UNKNOWN);
+    }
+
+    // constructor
+    lp_primal_core_solver(static_matrix<T, X> & A,
+                          vector<X> & b, // the right side vector
+                          vector<X> & x, // the number of elements in x needs to be at least as large as the number of columns in A
+                          vector<unsigned> & basis,
+                          vector<unsigned> & nbasis,
+                          vector<int> & heading,
+                          vector<T> & costs,
+                          const vector<column_type> & column_type_array,
+                          const vector<X> & upper_bound_values,
+                          lp_settings & settings,
+                          const column_namer& column_names):
+        lp_core_solver_base<T, X>(A, b,
+                                  basis,
+                                  nbasis,
+                                  heading,
+                                  x,
+                                  costs,
+                                  settings,
+                                  column_names,
+                                  column_type_array,
+                                  m_low_bounds_dummy,
+                                  upper_bound_values),
+        m_beta(A.row_count()),
+        m_converted_harris_eps(convert_struct<T, double>::convert(this->m_settings.harris_feasibility_tolerance)) {
+        lean_assert(initial_x_is_correct());
+        m_low_bounds_dummy.resize(A.column_count(), zero_of_type<T>());
+        m_enter_price_eps = numeric_traits<T>::precise() ? numeric_traits<T>::zero() : T(1e-5);
+#ifdef LEAN_DEBUG
+        // check_correctness();
+#endif
+    }
+
+    bool initial_x_is_correct() {
+        std::set<unsigned> basis_set;
+        for (unsigned i = 0; i < this->m_A.row_count(); i++) {
+            basis_set.insert(this->m_basis[i]);
+        }
+        for (unsigned j = 0; j < this->m_n(); j++) {
+            if (this->column_has_low_bound(j) && this->m_x[j] < numeric_traits<T>::zero()) {
+                LP_OUT(this->m_settings, "low bound for variable " << j << " does not hold: this->m_x[" << j << "] = " << this->m_x[j] << " is negative " << std::endl);
+                return false;
+            }
+
+            if (this->column_has_upper_bound(j) && this->m_x[j] > this->m_upper_bounds[j]) {
+                LP_OUT(this->m_settings, "upper bound for " << j << " does not hold: "  << this->m_upper_bounds[j] << ">" << this->m_x[j] << std::endl);
+                return false;
+            }
+
+            if (basis_set.find(j) != basis_set.end()) continue;
+            if (this->m_column_types[j] == column_type::low_bound)  {
+                if (numeric_traits<T>::zero() != this->m_x[j]) {
+                    LP_OUT(this->m_settings, "only low bound is set for " << j << " but low bound value " << numeric_traits<T>::zero() << " is not equal to " << this->m_x[j] << std::endl);
+                    return false;
+                }
+            }
+            if (this->m_column_types[j] == column_type::boxed) {
+                if (this->m_upper_bounds[j] != this->m_x[j] && !numeric_traits<T>::is_zero(this->m_x[j])) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+
+    friend core_solver_pretty_printer<T, X>;
+};
+}

src/util/lp/lp_primal_core_solver_instances.cpp

@@ -0,0 +1,25 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <utility>
+#include <memory>
+#include <string>
+#include "util/vector.h"
+#include <functional>
+#include "util/lp/lar_solver.h"
+#include "util/lp/lp_primal_core_solver.hpp"
+#include "util/lp/lp_primal_core_solver_tableau.hpp"
+namespace lean {
+template void lp_primal_core_solver<double, double>::find_feasible_solution();
+template void lean::lp_primal_core_solver<lean::mpq, lean::numeric_pair<lean::mpq> >::find_feasible_solution();
+
+template unsigned lp_primal_core_solver<double, double>::solve();
+template unsigned lp_primal_core_solver<double, double>::solve_with_tableau();
+template unsigned lp_primal_core_solver<mpq, mpq>::solve();
+template unsigned lp_primal_core_solver<mpq, numeric_pair<mpq> >::solve();
+template void lean::lp_primal_core_solver<double, double>::clear_breakpoints();
+template bool lean::lp_primal_core_solver<lean::mpq, lean::mpq>::update_basis_and_x_tableau(int, int, lean::mpq const&);
+template bool lean::lp_primal_core_solver<double, double>::update_basis_and_x_tableau(int, int, double const&);
+template bool lean::lp_primal_core_solver<lean::mpq, lean::numeric_pair<lean::mpq> >::update_basis_and_x_tableau(int, int, lean::numeric_pair<lean::mpq> const&);
+}

src/util/lp/lp_primal_core_solver_tableau.hpp

@@ -0,0 +1,393 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+// this is a part of lp_primal_core_solver that deals with the tableau
+#include "util/lp/lp_primal_core_solver.h"
+namespace lean {
+template <typename T, typename X> void lp_primal_core_solver<T, X>::one_iteration_tableau() {
+    int entering = choose_entering_column_tableau();
+    if (entering == -1) {
+        decide_on_status_when_cannot_find_entering();
+    }
+    else {
+        advance_on_entering_tableau(entering);
+    }
+    lean_assert(this->inf_set_is_correct());
+}
+
+template <typename T, typename X> void lp_primal_core_solver<T, X>::advance_on_entering_tableau(int entering) {
+    X t;
+    int leaving = find_leaving_and_t_tableau(entering, t);
+    if (leaving == -1) {
+        this->set_status(UNBOUNDED);
+        return;
+    }
+    advance_on_entering_and_leaving_tableau(entering, leaving, t);
+}
+/*
+template <typename T, typename X> int lp_primal_core_solver<T, X>::choose_entering_column_tableau_rows() {
+    int i = find_inf_row();
+    if (i == -1)
+        return -1;
+    return find_shortest_beneficial_column_in_row(i);
+ }
+*/
+ template <typename T, typename X> int lp_primal_core_solver<T, X>::choose_entering_column_tableau() {
+    //this moment m_y = cB * B(-1)
+    unsigned number_of_benefitial_columns_to_go_over =  get_number_of_non_basic_column_to_try_for_enter();
+    
+    lean_assert(numeric_traits<T>::precise());
+    if (number_of_benefitial_columns_to_go_over == 0)
+        return -1;
+    if (this->m_basis_sort_counter == 0) {
+        sort_non_basis();
+        this->m_basis_sort_counter = 20;
+    }
+    else {
+        this->m_basis_sort_counter--;
+    }
+    unsigned j_nz = this->m_m() + 1; // this number is greater than the max column size
+    std::list<unsigned>::iterator entering_iter = m_non_basis_list.end();
+    for (auto non_basis_iter = m_non_basis_list.begin(); number_of_benefitial_columns_to_go_over && non_basis_iter != m_non_basis_list.end(); ++non_basis_iter) {
+        unsigned j = *non_basis_iter;
+        if (!column_is_benefitial_for_entering_basis(j))
+            continue;
+
+        // if we are here then j is a candidate to enter the basis
+        unsigned t = this->m_A.number_of_non_zeroes_in_column(j);
+        if (t < j_nz) {
+            j_nz = t;
+            entering_iter = non_basis_iter;
+            if (number_of_benefitial_columns_to_go_over)
+                number_of_benefitial_columns_to_go_over--;
+        }
+        else if (t == j_nz && my_random() % 2 == 0) {
+            entering_iter = non_basis_iter;
+        }
+    }// while (number_of_benefitial_columns_to_go_over && initial_offset_in_non_basis != offset_in_nb);
+    if (entering_iter == m_non_basis_list.end())
+        return -1;
+    unsigned entering = *entering_iter;
+    m_sign_of_entering_delta = this->m_d[entering] > 0 ? 1 : -1;
+    if (this->m_using_infeas_costs && this->m_settings.use_breakpoints_in_feasibility_search)
+        m_sign_of_entering_delta = -m_sign_of_entering_delta;
+    m_non_basis_list.erase(entering_iter);
+    m_non_basis_list.push_back(entering);
+    return entering;
+
+}
+
+
+
+
+template <typename T, typename X>
+unsigned lp_primal_core_solver<T, X>::solve_with_tableau() {
+    init_run_tableau();
+    if (this->current_x_is_feasible() && this->m_look_for_feasible_solution_only) {
+        this->set_status(FEASIBLE);
+        return 0;
+    }
+        
+    if ((!numeric_traits<T>::precise()) && this->A_mult_x_is_off()) {
+        this->set_status(FLOATING_POINT_ERROR);
+        return 0;
+    }
+    do {
+        if (this->print_statistics_with_iterations_and_nonzeroes_and_cost_and_check_that_the_time_is_over((this->m_using_infeas_costs? "inf t" : "feas t"), * this->m_settings.get_message_ostream())) {
+            return this->total_iterations();
+        }
+        if (this->m_settings.use_tableau_rows())
+            one_iteration_tableau_rows();
+        else 
+            one_iteration_tableau();
+        switch (this->get_status()) {
+        case OPTIMAL:  // double check that we are at optimum
+        case INFEASIBLE:
+            if (this->m_look_for_feasible_solution_only && this->current_x_is_feasible())
+                break;
+            if (!numeric_traits<T>::precise()) {
+                if(this->m_look_for_feasible_solution_only)
+                    break;
+                this->init_lu();
+                
+                if (this->m_factorization->get_status() != LU_status::OK) {
+                    this->set_status(FLOATING_POINT_ERROR);
+                    break;
+                }
+                init_reduced_costs();
+                if (choose_entering_column(1) == -1) {
+                    decide_on_status_when_cannot_find_entering();
+                    break;
+                }
+                this->set_status(UNKNOWN);
+            } else { // precise case
+                if ((!this->infeasibility_costs_are_correct())) {
+                    init_reduced_costs_tableau(); // forcing recalc
+                    if (choose_entering_column_tableau() == -1) {
+                        decide_on_status_when_cannot_find_entering();
+                        break;
+                    }
+                    this->set_status(UNKNOWN);
+                }
+            }
+            break;
+        case TENTATIVE_UNBOUNDED:
+            this->init_lu();
+            if (this->m_factorization->get_status() != LU_status::OK) {
+                this->set_status(FLOATING_POINT_ERROR);
+                break;
+            }
+                
+            init_reduced_costs();
+            break;
+        case UNBOUNDED:
+            if (this->current_x_is_infeasible()) {
+                init_reduced_costs();
+                this->set_status(UNKNOWN);
+            }
+            break;
+
+        case UNSTABLE:
+            lean_assert(! (numeric_traits<T>::precise()));
+            this->init_lu();
+            if (this->m_factorization->get_status() != LU_status::OK) {
+                this->set_status(FLOATING_POINT_ERROR);
+                break;
+            }
+            init_reduced_costs();
+            break;
+
+        default:
+            break; // do nothing
+        }
+    } while (this->get_status() != FLOATING_POINT_ERROR
+             &&
+             this->get_status() != UNBOUNDED
+             &&
+             this->get_status() != OPTIMAL
+             &&
+             this->get_status() != INFEASIBLE
+             &&
+             this->m_iters_with_no_cost_growing <= this->m_settings.max_number_of_iterations_with_no_improvements
+             &&
+             this->total_iterations() <= this->m_settings.max_total_number_of_iterations
+             &&
+             !(this->current_x_is_feasible() && this->m_look_for_feasible_solution_only));
+
+    lean_assert(this->get_status() == FLOATING_POINT_ERROR
+                ||
+                this->current_x_is_feasible() == false
+                ||
+                this->calc_current_x_is_feasible_include_non_basis());
+    return this->total_iterations();
+
+}
+template <typename T, typename X>void lp_primal_core_solver<T, X>::advance_on_entering_and_leaving_tableau(int entering, int leaving, X & t) {
+    lean_assert(this->A_mult_x_is_off() == false);
+    lean_assert(leaving >= 0 && entering >= 0);
+    lean_assert((this->m_settings.simplex_strategy() ==
+                simplex_strategy_enum::tableau_rows) ||
+                m_non_basis_list.back() == static_cast<unsigned>(entering));
+    lean_assert(this->m_using_infeas_costs || !is_neg(t));
+    lean_assert(entering != leaving || !is_zero(t)); // otherwise nothing changes
+    if (entering == leaving) {
+        advance_on_entering_equal_leaving_tableau(entering, t);
+        return;
+    }
+    if (!is_zero(t)) {
+        if (this->current_x_is_feasible() || !this->m_settings.use_breakpoints_in_feasibility_search ) {
+            if (m_sign_of_entering_delta == -1)
+                t = -t;
+        }
+        this->update_basis_and_x_tableau(entering, leaving, t);
+        lean_assert(this->A_mult_x_is_off() == false);
+        this->m_iters_with_no_cost_growing = 0;
+    } else {
+        this->pivot_column_tableau(entering, this->m_basis_heading[leaving]);
+        this->change_basis(entering, leaving);
+    }
+
+    if (this->m_look_for_feasible_solution_only && this->current_x_is_feasible())
+        return;
+
+    if (this->m_settings.simplex_strategy() != simplex_strategy_enum::tableau_rows) {
+        if (need_to_switch_costs()) {
+            this->init_reduced_costs_tableau();
+        }
+        
+        lean_assert(!need_to_switch_costs());
+        std::list<unsigned>::iterator it = m_non_basis_list.end();
+        it--;
+        * it = static_cast<unsigned>(leaving);
+    }
+}
+
+template <typename T, typename X>
+void lp_primal_core_solver<T, X>::advance_on_entering_equal_leaving_tableau(int entering, X & t) {
+    lean_assert(!this->A_mult_x_is_off() );
+    this->update_x_tableau(entering, t * m_sign_of_entering_delta); 
+    if (this->m_look_for_feasible_solution_only && this->current_x_is_feasible())
+        return;
+    
+    if (need_to_switch_costs()) {
+        init_reduced_costs_tableau();
+    }
+    this->m_iters_with_no_cost_growing = 0;
+}
+template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_and_t_tableau(unsigned entering, X & t) {
+    unsigned k = 0;
+    bool unlimited = true;
+    unsigned row_min_nz = this->m_n() + 1;
+    m_leaving_candidates.clear();
+    auto & col = this->m_A.m_columns[entering];
+    unsigned col_size = col.size();
+    for (;k < col_size && unlimited; k++) {
+        const column_cell & c = col[k];
+        unsigned i = c.m_i;
+        const T & ed = this->m_A.get_val(c);
+        lean_assert(!numeric_traits<T>::is_zero(ed));
+        unsigned j = this->m_basis[i];
+        limit_theta_on_basis_column(j, - ed * m_sign_of_entering_delta, t, unlimited);
+        if (!unlimited) {
+            m_leaving_candidates.push_back(j);
+            row_min_nz = this->m_A.m_rows[i].size();
+        }
+    }
+    if (unlimited) {
+        if (try_jump_to_another_bound_on_entering_unlimited(entering, t))
+            return entering;
+        return -1;
+    }
+
+    X ratio;
+    for (;k < col_size; k++) {
+        const column_cell & c = col[k];
+        unsigned i = c.m_i;
+        const T & ed = this->m_A.get_val(c);
+         lean_assert(!numeric_traits<T>::is_zero(ed));
+        unsigned j = this->m_basis[i];
+        unlimited = true;
+        limit_theta_on_basis_column(j, -ed * m_sign_of_entering_delta, ratio, unlimited);
+        if (unlimited) continue;
+        unsigned i_nz = this->m_A.m_rows[i].size();
+        if (ratio < t) {
+            t = ratio;
+            m_leaving_candidates.clear();
+            m_leaving_candidates.push_back(j);
+            row_min_nz = i_nz;
+        } else if (ratio == t && i_nz < row_min_nz) {
+            m_leaving_candidates.clear();
+            m_leaving_candidates.push_back(j);
+            row_min_nz = this->m_A.m_rows[i].size();
+        } else if (ratio == t && i_nz == row_min_nz) {
+            m_leaving_candidates.push_back(j);
+        }
+    }
+
+    ratio = t;
+    unlimited = false;
+    if (try_jump_to_another_bound_on_entering(entering, t, ratio, unlimited)) {
+        t = ratio;
+        return entering;
+    }
+    if (m_leaving_candidates.size() == 1)
+        return m_leaving_candidates[0];
+    k = my_random() % m_leaving_candidates.size();
+    return m_leaving_candidates[k];
+}
+template <typename T, typename X> void lp_primal_core_solver<T, X>::init_run_tableau() {
+        //        print_matrix(&(this->m_A), std::cout);
+        lean_assert(this->A_mult_x_is_off() == false);
+        lean_assert(basis_columns_are_set_correctly());
+        this->m_basis_sort_counter = 0; // to initiate the sort of the basis
+        this->set_total_iterations(0);
+        this->m_iters_with_no_cost_growing = 0;
+		lean_assert(this->inf_set_is_correct());
+        if (this->current_x_is_feasible() && this->m_look_for_feasible_solution_only)
+            return;
+        if (this->m_settings.backup_costs)
+            backup_and_normalize_costs();
+        m_epsilon_of_reduced_cost = numeric_traits<X>::precise() ? zero_of_type<T>() : T(1) / T(10000000);
+        if (this->m_settings.use_breakpoints_in_feasibility_search)
+            m_breakpoint_indices_queue.resize(this->m_n());
+        if (!numeric_traits<X>::precise()) {
+            this->m_column_norm_update_counter = 0;
+            init_column_norms();
+        }
+        if (this->m_settings.m_simplex_strategy == simplex_strategy_enum::tableau_rows)
+            init_tableau_rows();
+        lean_assert(this->reduced_costs_are_correct_tableau());
+        lean_assert(!this->need_to_pivot_to_basis_tableau());
+}
+
+template <typename T, typename X> bool lp_primal_core_solver<T, X>::
+update_basis_and_x_tableau(int entering, int leaving, X const & tt) {
+    lean_assert(this->use_tableau());
+    update_x_tableau(entering, tt);
+    this->pivot_column_tableau(entering, this->m_basis_heading[leaving]);
+    this->change_basis(entering, leaving);
+    return true;
+}
+template <typename T, typename X> void lp_primal_core_solver<T, X>::
+update_x_tableau(unsigned entering, const X& delta) {
+    if (!this->m_using_infeas_costs) {
+        this->m_x[entering] += delta;
+        for (const auto & c : this->m_A.m_columns[entering]) {
+            unsigned i = c.m_i;
+            this->m_x[this->m_basis[i]] -= delta * this->m_A.get_val(c);
+            this->update_column_in_inf_set(this->m_basis[i]);
+        }
+    } else { // m_using_infeas_costs == true
+        this->m_x[entering] += delta;
+        lean_assert(this->column_is_feasible(entering));
+        lean_assert(this->m_costs[entering] == zero_of_type<T>());
+        // m_d[entering] can change because of the cost change for basic columns.
+        for (const auto & c : this->m_A.m_columns[entering]) {
+            unsigned i = c.m_i;
+            unsigned j = this->m_basis[i];
+            this->m_x[j] -= delta * this->m_A.get_val(c);
+            update_inf_cost_for_column_tableau(j);
+            if (is_zero(this->m_costs[j]))
+                this->m_inf_set.erase(j);
+            else
+                this->m_inf_set.insert(j);
+        }
+    }
+    lean_assert(this->A_mult_x_is_off() == false);
+}
+
+template <typename T, typename X> void lp_primal_core_solver<T, X>::
+update_inf_cost_for_column_tableau(unsigned j) {
+    lean_assert(this->m_settings.simplex_strategy() != simplex_strategy_enum::tableau_rows);
+    lean_assert(this->m_using_infeas_costs);
+    T new_cost = get_infeasibility_cost_for_column(j);
+    T delta = this->m_costs[j] - new_cost;
+    if (is_zero(delta))
+        return;
+    this->m_costs[j] = new_cost;
+    update_reduced_cost_for_basic_column_cost_change(delta, j);
+}
+
+template <typename T, typename X> void lp_primal_core_solver<T, X>::init_reduced_costs_tableau() {
+    if (this->current_x_is_infeasible() && !this->m_using_infeas_costs) {
+        init_infeasibility_costs();
+    } else if (this->current_x_is_feasible() && this->m_using_infeas_costs) {
+        if (this->m_look_for_feasible_solution_only)
+            return;
+        this->m_costs = m_costs_backup;
+        this->m_using_infeas_costs = false;
+    }
+    unsigned size = this->m_basis_heading.size();
+    for (unsigned j = 0; j < size; j++) {
+        if (this->m_basis_heading[j] >= 0)
+            this->m_d[j] = zero_of_type<T>();
+        else {
+            T& d = this->m_d[j] = this->m_costs[j];
+            for (auto & cc : this->m_A.m_columns[j]) {
+                d -= this->m_costs[this->m_basis[cc.m_i]] * this->m_A.get_val(cc);
+            }
+        }
+    }
+}
+}

src/util/lp/lp_primal_simplex.h

@@ -0,0 +1,96 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#pragma once
+#include "util/vector.h"
+#include <unordered_map>
+#include <string>
+#include <algorithm>
+#include "util/lp/lp_utils.h"
+#include "util/lp/column_info.h"
+#include "util/lp/lp_primal_core_solver.h"
+#include "util/lp/lp_solver.h"
+#include "util/lp/iterator_on_row.h"
+namespace lean {
+template <typename T, typename X>
+class lp_primal_simplex: public lp_solver<T, X> {
+    lp_primal_core_solver<T, X> * m_core_solver = nullptr;
+    vector<X> m_low_bounds;
+private:
+    unsigned original_rows() { return this->m_external_rows_to_core_solver_rows.size(); }
+
+    void fill_costs_and_x_for_first_stage_solver(unsigned original_number_of_columns);
+
+    void init_buffer(unsigned k, vector<T> & r);
+
+    void refactor();
+
+    void set_scaled_costs();
+public:
+    lp_primal_simplex() {}
+
+    column_info<T> * get_or_create_column_info(unsigned column);
+
+    void set_status(lp_status status) {
+        this->m_status = status;
+    }
+
+    lp_status get_status() {
+        return this->m_status;
+    }
+
+    void fill_acceptable_values_for_x();
+
+
+    void set_zero_bound(bool * bound_is_set, T * bounds,  unsigned i);
+
+    void fill_costs_and_x_for_first_stage_solver_for_row(
+                                                         int row,
+                                                         unsigned & slack_var,
+                                                         unsigned & artificial);
+
+
+
+    
+    void set_core_solver_bounds();
+
+    void update_time_limit_from_starting_time(int start_time) {
+        this->m_settings.time_limit -= (get_millisecond_span(start_time) / 1000.);
+    }
+
+    void find_maximal_solution();
+
+    void fill_A_x_and_basis_for_stage_one_total_inf();
+
+    void fill_A_x_and_basis_for_stage_one_total_inf_for_row(unsigned row);
+
+    void solve_with_total_inf();
+
+
+    ~lp_primal_simplex();
+
+    bool bounds_hold(std::unordered_map<std::string, T> const & solution);
+
+    T get_row_value(unsigned i, std::unordered_map<std::string, T> const & solution, std::ostream * out);
+
+    bool row_constraint_holds(unsigned i, std::unordered_map<std::string, T> const & solution, std::ostream * out);
+
+    bool row_constraints_hold(std::unordered_map<std::string, T> const & solution);
+
+
+    T * get_array_from_map(std::unordered_map<std::string, T> const & solution);
+
+    bool solution_is_feasible(std::unordered_map<std::string, T> const & solution) {
+        return bounds_hold(solution) && row_constraints_hold(solution);
+    }
+
+    virtual T get_column_value(unsigned column) const {
+        return this->get_column_value_with_core_solver(column, m_core_solver);
+    }
+
+    T get_current_cost() const;
+
+    
+};
+}

src/util/lp/lp_primal_simplex.hpp

@@ -0,0 +1,355 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <string>
+#include "util/vector.h"
+#include "util/lp/lp_primal_simplex.h"
+
+namespace lean {
+template <typename T, typename X> void lp_primal_simplex<T, X>::fill_costs_and_x_for_first_stage_solver(unsigned original_number_of_columns) {
+    unsigned slack_var = original_number_of_columns;
+    unsigned artificial = original_number_of_columns + this->m_slacks;
+
+    for (unsigned row = 0; row < this->row_count(); row++) {
+        fill_costs_and_x_for_first_stage_solver_for_row(row, slack_var, artificial);
+    }
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::init_buffer(unsigned k, vector<T> & r) {
+    for (unsigned i = 0; i < k; i++) {
+        r[i] = 0;
+    }
+    r[k] = 1;
+    for (unsigned i = this->row_count() -1; i > k; i--) {
+        r[i] = 0;
+    }
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::refactor() {
+    m_core_solver->init_lu();
+    if (m_core_solver->factorization()->get_status() != LU_status::OK) {
+        throw_exception("cannot refactor");
+    }
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::set_scaled_costs() {
+    unsigned j = this->number_of_core_structurals();
+    while (j-- > 0) {
+        this->set_scaled_cost(j);
+    }
+}
+
+template <typename T, typename X>     column_info<T> * lp_primal_simplex<T, X>::get_or_create_column_info(unsigned column) {
+    auto it = this->m_columns.find(column);
+    return (it == this->m_columns.end())? ( this->m_columns[column] = new column_info<T>) : it->second;
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::fill_acceptable_values_for_x() {
+    for (auto t : this->m_core_solver_columns_to_external_columns) {
+        this->m_x[t.first] = numeric_traits<T>::zero();
+    }
+}
+
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::set_zero_bound(bool * bound_is_set, T * bounds,  unsigned i) {
+    bound_is_set[i] = true;
+    bounds[i] = numeric_traits<T>::zero();
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::fill_costs_and_x_for_first_stage_solver_for_row(
+                                                                                                                int row,
+                                                                                                                unsigned & slack_var,
+                                                                                                                unsigned & artificial) {
+    lean_assert(row >= 0 && row < this->row_count());
+    auto & constraint = this->m_constraints[this->m_core_solver_rows_to_external_rows[row]];
+    // we need to bring the program to the form Ax = b
+    T rs = this->m_b[row];
+    T artificial_cost =  - numeric_traits<T>::one();
+    switch (constraint.m_relation) {
+    case Equal: // no slack variable here
+        this->m_column_types[artificial] = column_type::low_bound;
+        this->m_costs[artificial] = artificial_cost; // we are maximizing, so the artificial, which is non-negatiive, will be pushed to zero
+        this->m_basis[row] = artificial;
+        if (rs >= 0) {
+            (*this->m_A)(row, artificial) = numeric_traits<T>::one();
+            this->m_x[artificial] = rs;
+        } else {
+            (*this->m_A)(row, artificial) = - numeric_traits<T>::one();
+            this->m_x[artificial] = - rs;
+        }
+        artificial++;
+        break;
+
+    case Greater_or_equal:
+        this->m_column_types[slack_var] = column_type::low_bound;
+        (*this->m_A)(row, slack_var) = - numeric_traits<T>::one();
+
+        if (rs > 0) {
+            lean_assert(numeric_traits<T>::is_zero(this->m_x[slack_var]));
+            // adding one artificial
+            this->m_column_types[artificial] = column_type::low_bound;
+            (*this->m_A)(row, artificial) = numeric_traits<T>::one();
+            this->m_costs[artificial] = artificial_cost;
+            this->m_basis[row] = artificial;
+            this->m_x[artificial] = rs;
+            artificial++;
+        } else {
+            // we can put a slack_var into the basis, and atemplate <typename T, typename X> void lp_primal_simplex<T, X>::adding an artificial variable
+            this->m_basis[row] = slack_var;
+            this->m_x[slack_var] = - rs;
+        }
+        slack_var++;
+        break;
+    case Less_or_equal:
+        // introduce a non-negative slack variable
+        this->m_column_types[slack_var] = column_type::low_bound;
+        (*this->m_A)(row, slack_var) = numeric_traits<T>::one();
+
+        if (rs < 0) {
+            // adding one artificial
+            lean_assert(numeric_traits<T>::is_zero(this->m_x[slack_var]));
+            this->m_column_types[artificial] = column_type::low_bound;
+            (*this->m_A)(row, artificial) = - numeric_traits<T>::one();
+            this->m_costs[artificial] = artificial_cost;
+            this->m_x[artificial] = - rs;
+            this->m_basis[row] = artificial++;
+        } else {
+            // we can put slack_var into the basis, and atemplate <typename T, typename X> void lp_primal_simplex<T, X>::adding an artificial variable
+            this->m_basis[row] = slack_var;
+            this->m_x[slack_var] = rs;
+        }
+        slack_var++;
+        break;
+    }
+}
+
+
+
+
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::set_core_solver_bounds() {
+    unsigned total_vars = this->m_A->column_count() + this->m_slacks + this->m_artificials;
+    this->m_column_types.resize(total_vars);
+    this->m_upper_bounds.resize(total_vars);
+    for (auto cit : this->m_map_from_var_index_to_column_info) {
+        column_info<T> * ci = cit.second;
+        unsigned j = ci->get_column_index();
+        if (!is_valid(j))
+            continue; // the variable is not mapped to a column
+        switch (this->m_column_types[j] = ci->get_column_type()){
+        case column_type::fixed:
+            this->m_upper_bounds[j] = numeric_traits<T>::zero();
+            break;
+        case column_type::boxed:
+            this->m_upper_bounds[j] = ci->get_adjusted_upper_bound() / this->m_column_scale[j];
+            break;
+
+        default: break; // do nothing
+        }
+    }
+}
+
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::find_maximal_solution() {
+    int preprocessing_start_time = get_millisecond_count();
+    if (this->problem_is_empty()) {
+        this->m_status = lp_status::EMPTY;
+        return;
+    }
+
+    this->cleanup();
+    this->fill_matrix_A_and_init_right_side();
+    if (this->m_status == lp_status::INFEASIBLE) {
+        return;
+    }
+    this->m_x.resize(this->m_A->column_count());
+    this->fill_m_b();
+    this->scale();
+    fill_acceptable_values_for_x();
+    this->count_slacks_and_artificials();
+    set_core_solver_bounds();
+    update_time_limit_from_starting_time(preprocessing_start_time);
+    solve_with_total_inf();
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::fill_A_x_and_basis_for_stage_one_total_inf() {
+    for (unsigned row = 0; row < this->row_count(); row++)
+        fill_A_x_and_basis_for_stage_one_total_inf_for_row(row);
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::fill_A_x_and_basis_for_stage_one_total_inf_for_row(unsigned row) {
+    lean_assert(row < this->row_count());
+    auto ext_row_it = this->m_core_solver_rows_to_external_rows.find(row);
+    lean_assert(ext_row_it != this->m_core_solver_rows_to_external_rows.end());
+    unsigned ext_row = ext_row_it->second;
+    auto constr_it = this->m_constraints.find(ext_row);
+    lean_assert(constr_it != this->m_constraints.end());
+    auto & constraint = constr_it->second;
+    unsigned j = this->m_A->column_count(); // j is a slack variable
+    this->m_A->add_column();
+    // we need to bring the program to the form Ax = b
+    this->m_basis[row] = j;
+    switch (constraint.m_relation) {
+    case Equal:
+        this->m_x[j] = this->m_b[row];
+        (*this->m_A)(row, j) = numeric_traits<T>::one();
+        this->m_column_types[j] = column_type::fixed;
+        this->m_upper_bounds[j] = m_low_bounds[j] = zero_of_type<X>();
+        break;
+
+    case Greater_or_equal:
+        this->m_x[j] = - this->m_b[row];
+        (*this->m_A)(row, j) = - numeric_traits<T>::one();
+        this->m_column_types[j] = column_type::low_bound;
+        this->m_upper_bounds[j] = zero_of_type<X>();
+        break;
+    case Less_or_equal:
+        this->m_x[j] = this->m_b[row];
+        (*this->m_A)(row, j) = numeric_traits<T>::one();
+        this->m_column_types[j] = column_type::low_bound;
+        this->m_upper_bounds[j] = m_low_bounds[j] = zero_of_type<X>();
+        break;
+    default:
+        lean_unreachable();
+    }
+}
+
+template <typename T, typename X> void lp_primal_simplex<T, X>::solve_with_total_inf() {
+    int total_vars = this->m_A->column_count() + this->row_count();
+    if (total_vars == 0) {
+        this->m_status = OPTIMAL;
+        return;
+    }
+    m_low_bounds.clear();
+    m_low_bounds.resize(total_vars, zero_of_type<X>());  // low bounds are shifted ot zero
+    this->m_x.resize(total_vars, numeric_traits<T>::zero());
+    this->m_basis.resize(this->row_count());
+    this->m_costs.clear();
+    this->m_costs.resize(total_vars, zero_of_type<T>());
+    fill_A_x_and_basis_for_stage_one_total_inf();
+    if (this->m_settings.get_message_ostream() != nullptr)
+        this->print_statistics_on_A(*this->m_settings.get_message_ostream());
+    set_scaled_costs();
+
+    m_core_solver = new lp_primal_core_solver<T, X>(*this->m_A,
+                                                    this->m_b,
+                                                    this->m_x,
+                                                    this->m_basis,
+                                                    this->m_nbasis,
+                                                    this->m_heading,
+                                                    this->m_costs,
+                                                    this->m_column_types,
+                                                    m_low_bounds,
+                                                    this->m_upper_bounds,
+                                                    this->m_settings, *this);
+    m_core_solver->solve();
+    this->set_status(m_core_solver->get_status());
+    this->m_total_iterations = m_core_solver->total_iterations();   
+}
+
+
+template <typename T, typename X> lp_primal_simplex<T, X>::~lp_primal_simplex() {
+    if (m_core_solver != nullptr) {
+        delete m_core_solver;
+    }
+}
+
+template <typename T, typename X> bool lp_primal_simplex<T, X>::bounds_hold(std::unordered_map<std::string, T> const & solution) {
+    for (auto it : this->m_map_from_var_index_to_column_info) {
+        auto sol_it = solution.find(it.second->get_name());
+        if (sol_it == solution.end()) {
+            std::stringstream s;
+            s << "cannot find column " << it.first << " in solution";
+            throw_exception(s.str() );
+        }
+
+        if (!it.second->bounds_hold(sol_it->second)) {
+            //            std::cout << "bounds do not hold for " << it.second->get_name() << std::endl;
+            it.second->bounds_hold(sol_it->second);
+            return false;
+        }
+    }
+    return true;
+}
+
+template <typename T, typename X> T lp_primal_simplex<T, X>::get_row_value(unsigned i, std::unordered_map<std::string, T> const & solution, std::ostream * out) {
+    auto it = this->m_A_values.find(i);
+    if (it == this->m_A_values.end()) {
+        std::stringstream s;
+        s << "cannot find row " << i;
+        throw_exception(s.str() );
+    }
+    T ret = numeric_traits<T>::zero();
+    for (auto & pair : it->second) {
+        auto cit = this->m_map_from_var_index_to_column_info.find(pair.first);
+        lean_assert(cit != this->m_map_from_var_index_to_column_info.end());
+        column_info<T> * ci = cit->second;
+        auto sol_it = solution.find(ci->get_name());
+        lean_assert(sol_it != solution.end());
+        T column_val = sol_it->second;
+        if (out != nullptr) {
+            (*out) << pair.second << "(" << ci->get_name() << "=" << column_val << ") ";
+        }
+        ret += pair.second * column_val;
+    }
+    if (out != nullptr) {
+        (*out) << " = " << ret << std::endl;
+    }
+    return ret;
+}
+
+template <typename T, typename X> bool lp_primal_simplex<T, X>::row_constraint_holds(unsigned i, std::unordered_map<std::string, T> const & solution, std::ostream *out) {
+    T row_val = get_row_value(i, solution, out);
+    auto & constraint = this->m_constraints[i];
+    T rs = constraint.m_rs;
+    bool print = out != nullptr;
+    switch (constraint.m_relation) {
+    case Equal:
+        if (fabs(numeric_traits<T>::get_double(row_val - rs)) > 0.00001) {
+            if (print) {
+                (*out) << "should be = " << rs << std::endl;
+            }
+            return false;
+        }
+        return true;
+    case Greater_or_equal:
+        if (numeric_traits<T>::get_double(row_val - rs) < -0.00001) {
+            if (print) {
+                (*out) << "should be >= " << rs << std::endl;
+            }
+            return false;
+        }
+        return true;;
+
+    case Less_or_equal:
+        if (numeric_traits<T>::get_double(row_val - rs) > 0.00001) {
+            if (print) {
+                (*out) << "should be <= " << rs << std::endl;
+            }
+            return false;
+        }
+        return true;;
+    }
+    lean_unreachable();
+    return false; // it is unreachable
+}
+
+template <typename T, typename X> bool lp_primal_simplex<T, X>::row_constraints_hold(std::unordered_map<std::string, T> const & solution) {
+    for (auto it : this->m_A_values) {
+        if (!row_constraint_holds(it.first, solution, nullptr)) {
+            row_constraint_holds(it.first, solution, nullptr);
+            return false;
+        }
+    }
+    return true;
+}
+
+template <typename T, typename X> T lp_primal_simplex<T, X>::get_current_cost() const {
+    T ret = numeric_traits<T>::zero();
+    for (auto it : this->m_map_from_var_index_to_column_info) {
+        ret += this->get_column_cost_value(it.first, it.second);
+    }
+    return ret;
+}
+}

src/util/lp/lp_primal_simplex_instances.cpp

@@ -0,0 +1,20 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <utility>
+#include <memory>
+#include <string>
+#include "util/vector.h"
+#include <functional>
+#include "util/lp/lp_primal_simplex.hpp"
+template bool lean::lp_primal_simplex<double, double>::bounds_hold(std::unordered_map<std::string, double, std::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, double> > > const&);
+template bool lean::lp_primal_simplex<double, double>::row_constraints_hold(std::unordered_map<std::string, double, std::hash<std::string>, std::equal_to<std::string>, std::allocator<std::pair<std::string const, double> > > const&);
+template double lean::lp_primal_simplex<double, double>::get_current_cost() const;
+template double lean::lp_primal_simplex<double, double>::get_column_value(unsigned int) const;
+template lean::lp_primal_simplex<double, double>::~lp_primal_simplex();
+template lean::lp_primal_simplex<lean::mpq, lean::mpq>::~lp_primal_simplex();
+template lean::mpq lean::lp_primal_simplex<lean::mpq, lean::mpq>::get_current_cost() const;
+template lean::mpq lean::lp_primal_simplex<lean::mpq, lean::mpq>::get_column_value(unsigned int) const;
+template void lean::lp_primal_simplex<double, double>::find_maximal_solution();
+template void lean::lp_primal_simplex<lean::mpq, lean::mpq>::find_maximal_solution();

src/util/lp/lp_settings.h

@@ -0,0 +1,339 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+
+#pragma once
+#include "util/vector.h"
+#include <string>
+#include <algorithm>
+#include <limits>
+#include <sys/timeb.h>
+#include <iomanip>
+#include "util/lp/lp_utils.h"
+
+namespace lean {
+typedef unsigned var_index;
+typedef unsigned constraint_index;
+typedef unsigned row_index;
+enum class column_type  {
+    free_column = 0,
+        low_bound = 1,
+        upper_bound = 2,
+        boxed = 3,
+        fixed = 4
+        };
+
+enum class simplex_strategy_enum {
+    tableau_rows = 0,
+    tableau_costs = 1,
+    no_tableau = 2
+};
+
+std::string column_type_to_string(column_type t);
+
+enum lp_status {
+    UNKNOWN,
+    INFEASIBLE,
+    TENTATIVE_UNBOUNDED,
+    UNBOUNDED,
+    TENTATIVE_DUAL_UNBOUNDED,
+    DUAL_UNBOUNDED,
+    OPTIMAL,
+    FEASIBLE,
+    FLOATING_POINT_ERROR,
+    TIME_EXHAUSTED,
+    ITERATIONS_EXHAUSTED,
+    EMPTY,
+    UNSTABLE
+};
+
+// when the ratio of the vector lenth to domain size to is greater than the return value we switch to solve_By_for_T_indexed_only
+template <typename X>
+unsigned ratio_of_index_size_to_all_size() {
+    if (numeric_traits<X>::precise())
+        return 10;
+    return 120;
+}
+
+const char* lp_status_to_string(lp_status status);
+
+inline std::ostream& operator<<(std::ostream& out, lp_status status) {
+    return out << lp_status_to_string(status);
+}
+
+lp_status lp_status_from_string(std::string status);
+
+enum non_basic_column_value_position { at_low_bound, at_upper_bound, at_fixed, free_of_bounds, not_at_bound };
+
+template <typename X> bool is_epsilon_small(const X & v, const double& eps);    // forward definition
+
+int get_millisecond_count();
+int get_millisecond_span(int start_time);
+unsigned my_random();
+void my_random_init(long unsigned seed);
+
+
+class lp_resource_limit {
+public:
+    virtual bool get_cancel_flag() = 0;
+};
+
+struct stats {
+    unsigned m_total_iterations;
+    unsigned m_iters_with_no_cost_growing;
+    unsigned m_num_factorizations;
+    unsigned m_num_of_implied_bounds;
+    unsigned m_need_to_solve_inf;
+    stats() { reset(); }
+    void reset() { memset(this, 0, sizeof(*this)); }
+};
+
+struct lp_settings {
+private:
+    class default_lp_resource_limit : public lp_resource_limit {
+        lp_settings& m_settings;
+        int m_start_time;
+    public:
+        default_lp_resource_limit(lp_settings& s): m_settings(s), m_start_time(get_millisecond_count()) {}
+        virtual bool get_cancel_flag() {
+            int span_in_mills = get_millisecond_span(m_start_time);
+            return (span_in_mills / 1000.0  > m_settings.time_limit);
+        }
+    };
+
+    default_lp_resource_limit m_default_resource_limit;
+    lp_resource_limit* m_resource_limit;
+    // used for debug output
+    std::ostream* m_debug_out = &std::cout;
+    // used for messages, for example, the computation progress messages
+    std::ostream* m_message_out = &std::cout;
+
+    stats  m_stats;
+
+public:
+    unsigned reps_in_scaler = 20;
+    // when the absolute value of an element is less than pivot_epsilon
+    // in pivoting, we treat it as a zero
+    double pivot_epsilon = 0.00000001;
+    // see Chatal, page 115
+    double positive_price_epsilon = 1e-7;
+    // a quatation "if some choice of the entering vairable leads to an eta matrix
+    // whose diagonal element in the eta column is less than e2 (entering_diag_epsilon) in magnitude, the this choice is rejected ...
+    double entering_diag_epsilon = 1e-8;
+    int c_partial_pivoting = 10; // this is the constant c from page 410
+    unsigned depth_of_rook_search = 4;
+    bool using_partial_pivoting = true;
+    // dissertation of Achim Koberstein
+    // if Bx - b is different at any component more that refactor_epsilon then we refactor
+    double refactor_tolerance = 1e-4;
+    double pivot_tolerance = 1e-6;
+    double zero_tolerance = 1e-12;
+    double drop_tolerance = 1e-14;
+    double tolerance_for_artificials = 1e-4;
+    double can_be_taken_to_basis_tolerance = 0.00001;
+
+    unsigned percent_of_entering_to_check = 5; // we try to find a profitable column in a percentage of the columns
+    bool use_scaling = true;
+    double scaling_maximum = 1;
+    double scaling_minimum = 0.5;
+    double harris_feasibility_tolerance = 1e-7; // page 179 of Istvan Maros
+    double ignore_epsilon_of_harris = 10e-5;
+    unsigned max_number_of_iterations_with_no_improvements = 2000000;
+    unsigned max_total_number_of_iterations = 20000000;
+    double time_limit = std::numeric_limits<double>::max(); // the maximum time limit of the total run time in seconds
+    // dual section
+    double dual_feasibility_tolerance = 1e-7; // // page 71 of the PhD thesis of Achim Koberstein
+    double primal_feasibility_tolerance = 1e-7; // page 71 of the PhD thesis of Achim Koberstein
+    double relative_primal_feasibility_tolerance = 1e-9; // page 71 of the PhD thesis of Achim Koberstein
+
+    bool m_bound_propagation = true;
+    
+    bool bound_progation() const {
+        return m_bound_propagation;
+    }
+
+    bool& bound_propagation() {
+        return m_bound_propagation;
+    }
+    
+    lp_settings() : m_default_resource_limit(*this), m_resource_limit(&m_default_resource_limit) {}
+
+    void set_resource_limit(lp_resource_limit& lim) { m_resource_limit = &lim; }
+    bool get_cancel_flag() const { return m_resource_limit->get_cancel_flag(); }
+
+    void set_debug_ostream(std::ostream* out) { m_debug_out = out; }
+    void set_message_ostream(std::ostream* out) { m_message_out = out; }
+    
+    std::ostream* get_debug_ostream() { return m_debug_out; }
+    std::ostream* get_message_ostream() { return m_message_out; }
+    stats& st() { return m_stats; }
+    stats const& st() const { return m_stats; }
+
+    template <typename T> static bool is_eps_small_general(const T & t, const double & eps) {
+        return (!numeric_traits<T>::precise())? is_epsilon_small<T>(t, eps) : numeric_traits<T>::is_zero(t);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_dual_feasibility_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, dual_feasibility_tolerance);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_primal_feasibility_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, primal_feasibility_tolerance);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_can_be_taken_to_basis_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, can_be_taken_to_basis_tolerance);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_drop_tolerance(T const & t) const {
+        return is_eps_small_general<T>(t, drop_tolerance);
+    }
+
+
+    template <typename T>
+    bool abs_val_is_smaller_than_zero_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, zero_tolerance);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_refactor_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, refactor_tolerance);
+    }
+
+
+    template <typename T>
+    bool abs_val_is_smaller_than_pivot_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, pivot_tolerance);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_harris_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, harris_feasibility_tolerance);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_ignore_epslilon_for_harris(T const & t) {
+        return is_eps_small_general<T>(t, ignore_epsilon_of_harris);
+    }
+
+    template <typename T>
+    bool abs_val_is_smaller_than_artificial_tolerance(T const & t) {
+        return is_eps_small_general<T>(t, tolerance_for_artificials);
+    }
+    // the method of lar solver to use
+    bool presolve_with_double_solver_for_lar = true;
+    simplex_strategy_enum m_simplex_strategy = simplex_strategy_enum::tableau_rows;
+    simplex_strategy_enum simplex_strategy() const {
+        return m_simplex_strategy;
+    }
+
+    simplex_strategy_enum & simplex_strategy() {
+        return m_simplex_strategy;
+    }
+
+    bool use_tableau() const {
+        return m_simplex_strategy != simplex_strategy_enum::no_tableau;
+    }
+
+    bool use_tableau_rows() const {
+        return m_simplex_strategy == simplex_strategy_enum::tableau_rows;
+    }
+    
+    int report_frequency = 1000;
+    bool print_statistics = false;
+    unsigned column_norms_update_frequency = 12000;
+    bool scale_with_ratio = true;
+    double density_threshold = 0.7; // need to tune it up, todo
+#ifdef LEAN_DEBUG
+    static unsigned ddd; // used for debugging    
+#endif
+    bool use_breakpoints_in_feasibility_search = false;
+    unsigned random_seed = 1;
+    static unsigned long random_next;
+    unsigned max_row_length_for_bound_propagation = 300;
+    bool backup_costs = true;
+}; // end of lp_settings class
+
+
+#define LP_OUT(_settings_, _msg_) { if (_settings_.get_debug_ostream()) { *_settings_.get_debug_ostream() << _msg_; } }
+
+template <typename T>
+std::string T_to_string(const T & t) {
+    std::ostringstream strs;
+    strs << t;
+    return strs.str();
+}
+
+inline std::string T_to_string(const numeric_pair<mpq> & t) {
+    std::ostringstream strs;
+    double r = (t.x + t.y / mpq(1000)).get_double();
+    strs << r;
+    return strs.str();
+}
+
+
+inline std::string T_to_string(const mpq & t) {
+    std::ostringstream strs;
+    strs << t.get_double();
+    return strs.str();
+}
+
+template <typename T>
+bool val_is_smaller_than_eps(T const & t, double const & eps) {
+    if (!numeric_traits<T>::precise()) {
+        return numeric_traits<T>::get_double(t) < eps;
+    }
+    return t <= numeric_traits<T>::zero();
+}
+
+template <typename T>
+bool vectors_are_equal(T * a, vector<T>  &b, unsigned n);
+
+template <typename T>
+bool vectors_are_equal(const vector<T> & a, const buffer<T>  &b);
+
+template <typename T>
+bool vectors_are_equal(const vector<T> & a, const vector<T> &b);
+
+template <typename T>
+T abs (T const & v) { return v >= zero_of_type<T>() ? v : -v; }
+
+template <typename X>
+X max_abs_in_vector(vector<X>& t){
+    X r(zero_of_type<X>());
+    for (auto & v : t)
+        r = std::max(abs(v) , r);
+    return r;
+}
+inline void print_blanks(int n, std::ostream & out) {
+    while (n--) {out << ' '; }
+}
+
+
+// after a push of the last element we ensure that the vector increases
+// we also suppose that before the last push the vector was increasing
+inline void ensure_increasing(vector<unsigned> & v) {
+    lean_assert(v.size() > 0);
+    unsigned j = v.size() - 1;
+    for (; j > 0; j-- )
+        if (v[j] <= v[j - 1]) {
+            // swap
+            unsigned t = v[j];
+            v[j] = v[j-1];
+            v[j-1] = t;
+        } else {
+            break;
+        }
+}
+
+
+
+#if LEAN_DEBUG
+bool D();
+#endif
+}

src/util/lp/lp_settings.hpp

@@ -0,0 +1,133 @@
+/*
+  Copyright (c) 2017 Microsoft Corporation
+  Author: Lev Nachmanson
+*/
+#include <cmath>
+#include <string>
+#include "util/vector.h"
+#include "util/lp/lp_settings.h"
+namespace lean {
+std::string column_type_to_string(column_type t) {
+    switch (t) {
+    case column_type::fixed:       return "fixed";
+    case column_type::boxed:       return "boxed";
+    case column_type::low_bound:   return "low_bound";
+    case column_type::upper_bound: return "upper_bound";
+    case column_type::free_column: return "free_column";
+    default:  lean_unreachable();
+    }
+    return "unknown"; // it is unreachable
+}
+
+const char* lp_status_to_string(lp_status status) {
+    switch (status) {
+    case UNKNOWN: return "UNKNOWN";
+    case INFEASIBLE: return "INFEASIBLE";
+    case UNBOUNDED: return "UNBOUNDED";
+    case TENTATIVE_DUAL_UNBOUNDED: return "TENTATIVE_DUAL_UNBOUNDED";
+    case DUAL_UNBOUNDED: return "DUAL_UNBOUNDED";
+    case OPTIMAL: return "OPTIMAL";
+    case FEASIBLE: return "FEASIBLE";
+    case FLOATING_POINT_ERROR: return "FLOATING_POINT_ERROR";
+    case TIME_EXHAUSTED: return "TIME_EXHAUSTED";
+    case ITERATIONS_EXHAUSTED: return "ITERATIONS_EXHAUSTED";
+    case EMPTY: return "EMPTY";
+    case UNSTABLE: return "UNSTABLE";
+    default:
+        lean_unreachable();
+    }
+    return "UNKNOWN";  // it is unreachable
+}
+
+lp_status lp_status_from_string(std::string status) {
+    if (status == "UNKNOWN") return  lp_status::UNKNOWN;
+    if (status == "INFEASIBLE") return lp_status::INFEASIBLE;
+    if (status == "UNBOUNDED") return lp_status::UNBOUNDED;
+    if (status == "OPTIMAL") return lp_status::OPTIMAL;
+    if (status == "FEASIBLE") return lp_status::FEASIBLE;
+    if (status == "FLOATING_POINT_ERROR") return lp_status::FLOATING_POINT_ERROR;
+    if (status == "TIME_EXHAUSTED") return lp_status::TIME_EXHAUSTED;
+    if (status == "ITERATIONS_EXHAUSTED") return lp_status::ITERATIONS_EXHAUSTED;
+    if (status == "EMPTY") return lp_status::EMPTY;
+    lean_unreachable();
+    return lp_status::UNKNOWN; // it is unreachable
+}
+int get_millisecond_count() {
+    timeb tb;
+    ftime(&tb);
+    return tb.millitm + (tb.time & 0xfffff) * 1000;
+}
+
+int get_millisecond_span(int start_time) {
+    int span = get_millisecond_count() - start_time;
+    if (span < 0)
+        span += 0x100000 * 1000;
+    return span;
+}
+
+
+
+void my_random_init(long unsigned seed) {
+    lp_settings::random_next = seed;   
+}
+
+unsigned my_random() {
+    lp_settings::random_next = lp_settings::random_next * 1103515245 + 12345;
+    return((unsigned)(lp_settings::random_next/65536) % 32768);
+}
+
+template <typename T>
+bool vectors_are_equal(T * a, vector<T>  &b, unsigned n) {
+    if (numeric_traits<T>::precise()) {
+        for (unsigned i = 0; i < n; i ++){
+            if (!numeric_traits<T>::is_zero(a[i] - b[i])) {
+                // std::cout << "a[" << i <<"]" << a[i] << ", " << "b[" << i <<"]" << b[i] << std::endl;
+                return false;
+            }
+        }
+    } else {
+        for (unsigned i = 0; i < n; i ++){
+            if (std::abs(numeric_traits<T>::get_double(a[i] - b[i])) > 0.000001) {
+                // std::cout << "a[" << i <<"]" << a[i] << ", " << "b[" << i <<"]" << b[i] << std::endl;
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+
+template <typename T>
+bool vectors_are_equal(const vector<T> & a, const vector<T>  &b) {
+    unsigned n = static_cast<unsigned>(a.size());
+    if (n != b.size()) return false;
+    if (numeric_traits<T>::precise()) {
+        for (unsigned i = 0; i < n; i ++){
+            if (!numeric_traits<T>::is_zero(a[i] - b[i])) {
+                // std::cout << "a[" << i <<"]" << a[i] << ", " << "b[" << i <<"]" << b[i] << std::endl;
+                return false;
+            }
+        }
+    } else {
+        for (unsigned i = 0; i < n; i ++){
+            double da = numeric_traits<T>::get_double(a[i]);
+            double db = numeric_traits<T>::get_double(b[i]);
+            double amax = std::max(fabs(da), fabs(db));
+            if (amax > 1) {
+                da /= amax;
+                db /= amax;
+            }
+                
+            if (fabs(da - db) > 0.000001) {
+                // std::cout << "a[" << i <<"] = " << a[i] << ", but " << "b[" << i <<"] = " << b[i] << std::endl;
+                return false;
+            }
+        }
+    }
+    return true;
+}
+unsigned long lp_settings::random_next = 1;
+#ifdef LEAN_DEBUG
+unsigned lp_settings::ddd = 0;
+#endif
+}