diff --git a/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.cpp b/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.cpp
index bcef44440..30cfddcd4 100644
--- a/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.cpp
+++ b/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.cpp
@@ -15,9 +15,6 @@ Author:
 
 Notes:
 
-    TBD: also keep track of which fresh constants are introduced
-    to instruct model converter to delete them.
-
 --*/
 #include "ast/rewriter/bit_blaster/bit_blaster_rewriter.h"
 #include "ast/bv_decl_plugin.h"
@@ -95,6 +92,8 @@ struct blaster_rewriter_cfg : public default_rewriter_cfg {
     func_decl_ref_vector                     m_keys;
     expr_ref_vector                          m_values;
     unsigned_vector                          m_keyval_lim;
+    func_decl_ref_vector                     m_newbits;
+    unsigned_vector                          m_newbits_lim;
 
     bool                                     m_blast_mul;
     bool                                     m_blast_add;
@@ -121,7 +120,8 @@ struct blaster_rewriter_cfg : public default_rewriter_cfg {
         m_out(m),
         m_bindings(m),
         m_keys(m),
-        m_values(m) {
+        m_values(m),
+        m_newbits(m) {
         updt_params(p);
     }
 
@@ -163,6 +163,7 @@ struct blaster_rewriter_cfg : public default_rewriter_cfg {
 
     void push() {
         m_keyval_lim.push_back(m_keys.size());
+        m_newbits_lim.push_back(m_newbits.size());
     }
 
     unsigned get_num_scopes() const {
@@ -181,6 +182,10 @@ struct blaster_rewriter_cfg : public default_rewriter_cfg {
             m_keys.resize(lim);
             m_values.resize(lim);
             m_keyval_lim.resize(new_sz);
+
+            lim = m_newbits_lim[new_sz];
+            m_newbits.shrink(lim);
+            m_newbits_lim.shrink(new_sz);
         }
     }
 
@@ -189,10 +194,13 @@ struct blaster_rewriter_cfg : public default_rewriter_cfg {
     void start_rewrite() {
         m_keypos = m_keys.size();
     }
-    void end_rewrite(obj_map<func_decl, expr*>& const2bits) {
+
+    void end_rewrite(obj_map<func_decl, expr*>& const2bits, ptr_vector<func_decl> & newbits) {
         for (unsigned i = m_keypos; i < m_keys.size(); ++i) {
             const2bits.insert(m_keys[i].get(), m_values[i].get());
         }
+        for (func_decl* f : m_newbits) newbits.push_back(f);
+        
     }
 
     template<typename V>
@@ -215,6 +223,7 @@ struct blaster_rewriter_cfg : public default_rewriter_cfg {
         m_out.reset();
         for (unsigned i = 0; i < bv_size; i++) {
             m_out.push_back(m().mk_fresh_const(0, b));
+            m_newbits.push_back(to_app(m_out.back())->get_decl());
         }
         r = mk_mkbv(m_out);
         m_const2bits.insert(f, r);
@@ -650,7 +659,7 @@ struct bit_blaster_rewriter::imp : public rewriter_tpl<blaster_rewriter_cfg> {
     void push() { m_cfg.push(); }
     void pop(unsigned s) { m_cfg.pop(s); }
     void start_rewrite() { m_cfg.start_rewrite(); }
-    void end_rewrite(obj_map<func_decl, expr*>& const2bits) { m_cfg.end_rewrite(const2bits); }
+    void end_rewrite(obj_map<func_decl, expr*>& const2bits, ptr_vector<func_decl> & newbits) { m_cfg.end_rewrite(const2bits, newbits); }
     unsigned get_num_scopes() const { return m_cfg.get_num_scopes(); }
 };
 
@@ -703,6 +712,6 @@ void bit_blaster_rewriter::start_rewrite() {
     m_imp->start_rewrite();
 }
 
-void bit_blaster_rewriter::end_rewrite(obj_map<func_decl, expr*>& const2bits) {
-    m_imp->end_rewrite(const2bits);
+void bit_blaster_rewriter::end_rewrite(obj_map<func_decl, expr*>& const2bits, ptr_vector<func_decl> & newbits) {
+    m_imp->end_rewrite(const2bits, newbits);
 }
diff --git a/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.h b/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.h
index 2463bd086..24b6b0c0a 100644
--- a/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.h
+++ b/src/ast/rewriter/bit_blaster/bit_blaster_rewriter.h
@@ -33,13 +33,15 @@ public:
     ast_manager & m() const;
     unsigned get_num_steps() const;
     void cleanup();
-    obj_map<func_decl, expr*> const& const2bits() const;     
     void start_rewrite();
-    void end_rewrite(obj_map<func_decl, expr*>& const2bits);
+    void end_rewrite(obj_map<func_decl, expr*>& const2bits, ptr_vector<func_decl> & newbits);
     void operator()(expr * e, expr_ref & result, proof_ref & result_proof);
     void push();
     void pop(unsigned num_scopes);
     unsigned get_num_scopes() const;
+private:
+    obj_map<func_decl, expr*> const& const2bits() const;     
+
 };
 
 #endif
diff --git a/src/ast/rewriter/pb_rewriter.cpp b/src/ast/rewriter/pb_rewriter.cpp
index 42efb3c6c..f549b944b 100644
--- a/src/ast/rewriter/pb_rewriter.cpp
+++ b/src/ast/rewriter/pb_rewriter.cpp
@@ -255,11 +255,11 @@ br_status pb_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * cons
         rational slack(0);
         m_args.reset();
         m_coeffs.reset();
-        for (unsigned i = 0; i < sz; ++i) {
-            m_args.push_back(vec[i].first);
-            m_coeffs.push_back(vec[i].second);
-            SASSERT(vec[i].second.is_pos());
-            slack += vec[i].second;
+        for (auto const& kv : vec) {
+            m_args.push_back(kv.first);
+            m_coeffs.push_back(kv.second);
+            SASSERT(kv.second.is_pos());
+            slack += kv.second;
             all_unit &= m_coeffs.back().is_one();
         }
         if (is_eq) {
@@ -287,7 +287,9 @@ br_status pb_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * cons
         }
         else {
             expr_ref_vector conj(m), disj(m);
-            for (unsigned i = 0; i < m_args.size(); ++i) {
+            unsigned j = 0; 
+            sz = m_args.size();
+            for (unsigned i = 0; i < sz; ++i) {
                 rational& c = m_coeffs[i];
                 if (slack < c + k) {
                     conj.push_back(m_args[i]);
@@ -299,29 +301,25 @@ br_status pb_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * cons
                     disj.push_back(m_args[i]);
                 }
                 else {
-                    continue;
+                    m_args[j] = m_args[i];
+                    m_coeffs[j] = m_coeffs[i];
+                    ++j;
                 }
-                m_args[i] = m_args.back();
-                m_coeffs[i] = m_coeffs.back();
-                --i;
-                m_args.pop_back();
-                m_coeffs.pop_back();
             }
-            sz = m_coeffs.size();
-            if (slack < k) {
-                conj.push_back(m.mk_false());
+            m_args.shrink(j);
+            m_coeffs.shrink(j);
+            sz = j;
+            if (k.is_pos() && sz > 0 && slack >= k) {
+                disj.push_back(m_util.mk_ge(sz, m_coeffs.c_ptr(), m_args.c_ptr(), k));
             }
-            else if (k.is_pos() && sz > 0) {
-                conj.push_back(m_util.mk_ge(sz, m_coeffs.c_ptr(), m_args.c_ptr(), k));
+            if (!disj.empty()) {
+                conj.push_back(mk_or(disj));
             }
             result = mk_and(conj);
-            if (!disj.empty()) {
-                disj.push_back(result);
-                result = mk_or(disj);
-            }
-            if (!disj.empty() || conj.size() > 1) {
+
+            if (disj.size() > 1 || conj.size() > 1) {               
                 st = BR_REWRITE3;
-            }
+            }            
         }
         break;
     }
diff --git a/src/ast/rewriter/pb_rewriter_def.h b/src/ast/rewriter/pb_rewriter_def.h
index aa2c2a61f..e4a7e012d 100644
--- a/src/ast/rewriter/pb_rewriter_def.h
+++ b/src/ast/rewriter/pb_rewriter_def.h
@@ -45,25 +45,25 @@ void pb_rewriter_util<PBU>::unique(typename PBU::args_t& args, typename PBU::num
         }
     }
     // remove constants
-    for (unsigned i = 0; i < args.size(); ++i) {
+    unsigned j = 0, sz = args.size();
+    for (unsigned i = 0; i < sz; ++i) {
         if (m_util.is_true(args[i].first)) {
             k -= args[i].second;
-            std::swap(args[i], args[args.size()-1]);
-            args.pop_back();
-            --i;
         }
         else if (m_util.is_false(args[i].first)) {
-            std::swap(args[i], args[args.size()-1]);
-            args.pop_back();                
-            --i;
+            // no-op
+        }
+        else {
+            args[j++] = args[i];
         }
     }
+    args.shrink(j);
     // sort and coalesce arguments:
     typename PBU::compare cmp;
     std::sort(args.begin(), args.end(), cmp);
 
     // coallesce
-    unsigned i, j;
+    unsigned i;
     for (i = 0, j = 1; j < args.size(); ++j) {
         if (args[i].first == args[j].first) {
             args[i].second += args[j].second;
diff --git a/src/opt/maxsmt.cpp b/src/opt/maxsmt.cpp
index 636bbf9f9..ef264eb9e 100644
--- a/src/opt/maxsmt.cpp
+++ b/src/opt/maxsmt.cpp
@@ -266,7 +266,7 @@ namespace opt {
             }
         }
 
-        IF_VERBOSE(1, verbose_stream() << "is-sat: " << is_sat << "\n";
+        IF_VERBOSE(5, verbose_stream() << "is-sat: " << is_sat << "\n";
                    if (is_sat == l_true) {
                        verbose_stream() << "Satisfying soft constraints\n";
                        display_answer(verbose_stream());
diff --git a/src/opt/opt_context.cpp b/src/opt/opt_context.cpp
index ec2059642..8cbcbed5e 100644
--- a/src/opt/opt_context.cpp
+++ b/src/opt/opt_context.cpp
@@ -17,6 +17,7 @@ Notes:
 
 --*/
 
+#include "util/gparams.h"
 #include "ast/for_each_expr.h"
 #include "ast/ast_pp.h"
 #include "ast/bv_decl_plugin.h"
@@ -125,7 +126,7 @@ namespace opt {
         m_box_index(UINT_MAX),
         m_optsmt(m),
         m_scoped_state(m),
-        m_fm(m, "opt"),
+        m_fm(alloc(generic_model_converter, m, "opt")),
         m_objective_refs(m),
         m_enable_sat(false),
         m_is_clausal(false),
@@ -277,9 +278,12 @@ namespace opt {
         if (is_sat != l_false) {
             s.get_model(m_model);
             s.get_labels(m_labels);
+            if (is_sat == l_true) {
+                validate_model();
+            }
         }
         if (is_sat != l_true) {
-            TRACE("opt", tout << m_hard_constraints << "\n";);
+            TRACE("opt", tout << m_hard_constraints << "\n";);            
             return is_sat;
         }
         IF_VERBOSE(1, verbose_stream() << "(optimize:sat)\n";);
@@ -308,6 +312,7 @@ namespace opt {
             break;
         }
         }
+        if (is_sat == l_true) validate_model();
         return adjust_unknown(is_sat);
     }
 
@@ -324,8 +329,8 @@ namespace opt {
 
     void context::fix_model(model_ref& mdl) {
         if (mdl) {
+            (*m_fm)(mdl);
             apply(m_model_converter, mdl);
-            m_fm(mdl);
         }
     }
 
@@ -568,7 +573,7 @@ namespace opt {
 
     void context::init_solver() {
         setup_arith_solver();
-        m_opt_solver = alloc(opt_solver, m, m_params, m_fm);
+        m_opt_solver = alloc(opt_solver, m, m_params, *m_fm);
         m_opt_solver->set_logic(m_logic);
         m_solver = m_opt_solver.get();
         m_opt_solver->ensure_pb();
@@ -792,13 +797,13 @@ namespace opt {
                     offset -= weight;
                 }
                 if (m.is_true(arg)) {
-                    IF_VERBOSE(1, verbose_stream() << weight << ": " << mk_pp(m_objectives[index].m_terms[i].get(), m) << " |-> true\n";);
+                    IF_VERBOSE(5, verbose_stream() << weight << ": " << mk_pp(m_objectives[index].m_terms[i].get(), m) << " |-> true\n";);
                 }
                 else if (weight.is_zero()) {
                     // skip
                 }
                 else if (m.is_false(arg)) {
-                    IF_VERBOSE(1, verbose_stream() << weight << ": " << mk_pp(m_objectives[index].m_terms[i].get(), m) << " |-> false\n";);
+                    IF_VERBOSE(5, verbose_stream() << weight << ": " << mk_pp(m_objectives[index].m_terms[i].get(), m) << " |-> false\n";);
                     offset += weight;
                 }
                 else {
@@ -924,8 +929,7 @@ namespace opt {
         TRACE("opt", tout << fmls << "\n";);
         m_hard_constraints.reset();
         expr_ref orig_term(m);
-        for (unsigned i = 0; i < fmls.size(); ++i) {
-            expr* fml = fmls[i];
+        for (expr * fml : fmls) {
             app_ref tr(m);
             expr_ref_vector terms(m);
             vector<rational> weights;
@@ -1110,8 +1114,7 @@ namespace opt {
     }
 
     void context::internalize() {
-        for (unsigned i = 0; i < m_objectives.size(); ++i) {
-            objective & obj = m_objectives[i];
+        for (objective & obj : m_objectives) {
             switch(obj.m_type) {
             case O_MINIMIZE: {
                 app_ref tmp(m);
@@ -1397,21 +1400,21 @@ namespace opt {
     }
 
     std::string context::to_string() const {
-        return to_string(m_scoped_state.m_hard, m_scoped_state.m_objectives);
+        return to_string(false, m_scoped_state.m_hard, m_scoped_state.m_objectives);
     }
 
     std::string context::to_string_internal() const {
-        return to_string(m_hard_constraints, m_objectives);
+        return to_string(true, m_hard_constraints, m_objectives);
     }
 
-    std::string context::to_string(expr_ref_vector const& hard, vector<objective> const& objectives) const {
+    std::string context::to_string(bool is_internal, expr_ref_vector const& hard, vector<objective> const& objectives) const {
         smt2_pp_environment_dbg env(m);
         ast_pp_util visitor(m);
         std::ostringstream out;
         visitor.collect(hard);
+        model_converter_ref mc = concat(m_model_converter.get(), m_fm.get());
                 
-        for (unsigned i = 0; i < objectives.size(); ++i) {
-            objective const& obj = objectives[i];
+        for (objective const& obj : objectives) {
             switch(obj.m_type) {
             case O_MAXIMIZE: 
             case O_MINIMIZE:
@@ -1426,10 +1429,16 @@ namespace opt {
             }
         }
 
+        if (is_internal && mc) { 
+            mc->collect(visitor); 
+        }
+
+        param_descrs descrs;
+        collect_param_descrs(descrs);
+        m_params.display_smt2(out, "opt", descrs);
         visitor.display_decls(out);
         visitor.display_asserts(out, hard, m_pp_neat);
-        for (unsigned i = 0; i < objectives.size(); ++i) {
-            objective const& obj = objectives[i];
+        for (objective const& obj : objectives) {
             switch(obj.m_type) {
             case O_MAXIMIZE: 
                 out << "(maximize ";
@@ -1464,15 +1473,33 @@ namespace opt {
                 break;
             }
         }        
-        
-        param_descrs descrs;
-        collect_param_descrs(descrs);
-        m_params.display_smt2(out, "opt", descrs);
-        
+        if (is_internal && mc) {
+            mc->display(out);
+        }
+                
         out << "(check-sat)\n"; 
         return out.str();
     }
 
+    void context::validate_model() {
+        if (!gparams::get().get_bool("model_validate", false)) return;
+        expr_ref_vector fmls(m);
+        get_hard_constraints(fmls);
+        expr_ref tmp(m);
+        model_ref mdl;
+        get_model(mdl);
+        for (expr * f : fmls) {
+            if (!mdl->eval(f, tmp) || !m.is_true(tmp)) {
+                //IF_VERBOSE(0, m_fm->display(verbose_stream() << "fm\n"));
+                //IF_VERBOSE(0, m_model_converter->display(verbose_stream() << "mc\n"));
+                IF_VERBOSE(0, verbose_stream() << "Failed to validate " << mk_pp(f, m) << "\n" << tmp << "\n");
+                //IF_VERBOSE(0, model_smt2_pp(verbose_stream(), m, *mdl, 0)); 
+                IF_VERBOSE(11, verbose_stream() << to_string_internal() << "\n");
+                exit(0);
+            }
+        }
+    }
+
     void context::validate_maxsat(symbol const& id) {
         maxsmt& ms = *m_maxsmts.find(id);
         TRACE("opt", tout << "Validate: " << id << "\n";);
@@ -1551,8 +1578,8 @@ namespace opt {
         if (!m_arith.is_real(m_objectives[0].m_term)) {
             return false;
         }
-        for (unsigned i = 0; i < m_hard_constraints.size(); ++i) {
-            if (has_quantifiers(m_hard_constraints[i].get())) {
+        for (expr* fml : m_hard_constraints) {
+            if (has_quantifiers(fml)) {
                 return true;
             }
         }
diff --git a/src/opt/opt_context.h b/src/opt/opt_context.h
index be0ef873c..e4d1f8e2d 100644
--- a/src/opt/opt_context.h
+++ b/src/opt/opt_context.h
@@ -155,7 +155,7 @@ namespace opt {
         vector<objective>   m_objectives;
         model_ref           m_model;
         model_converter_ref          m_model_converter;
-        generic_model_converter       m_fm;
+        generic_model_converter_ref  m_fm;
         obj_map<func_decl, unsigned> m_objective_fns;
         obj_map<func_decl, expr*>    m_objective_orig;
         func_decl_ref_vector         m_objective_refs;
@@ -219,7 +219,7 @@ namespace opt {
         virtual expr_ref mk_le(unsigned i, model_ref& model);
 
         virtual smt::context& smt_context() { return m_opt_solver->get_context(); }
-        virtual generic_model_converter& fm() { return m_fm; }
+        virtual generic_model_converter& fm() { return *m_fm; }
         virtual bool sat_enabled() const { return 0 != m_sat_solver.get(); }
         virtual solver& get_solver();
         virtual ast_manager& get_manager() const { return this->m; }
@@ -290,12 +290,13 @@ namespace opt {
         void display_objective(std::ostream& out, objective const& obj) const;
         void display_bounds(std::ostream& out, bounds_t const& b) const;
 
-        std::string to_string(expr_ref_vector const& hard, vector<objective> const& objectives) const;
+        std::string to_string(bool is_internal, expr_ref_vector const& hard, vector<objective> const& objectives) const;
         std::string to_string_internal() const;
 
 
         void validate_lex();
         void validate_maxsat(symbol const& id);
+        void validate_model();
 
         void display_benchmark();
 
diff --git a/src/sat/ba_solver.cpp b/src/sat/ba_solver.cpp
index 3ef422d6a..ebc198e61 100644
--- a/src/sat/ba_solver.cpp
+++ b/src/sat/ba_solver.cpp
@@ -20,6 +20,7 @@ Revision History:
 #include "sat/ba_solver.h"
 #include "sat/sat_types.h"
 #include "util/mpz.h"
+#include "sat/sat_simplifier_params.hpp"
 
 
 namespace sat {
@@ -3013,19 +3014,21 @@ namespace sat {
     }
     
     unsigned ba_solver::set_non_external() {
+        sat_simplifier_params p(s().m_params);
         // set variables to be non-external if they are not used in theory constraints.
         unsigned ext = 0;
-        for (unsigned v = 0; v < s().num_vars(); ++v) {
+        bool incremental_mode = s().get_config().m_incremental && !p.override_incremental();
+        incremental_mode |=  s().tracking_assumptions();
+        for (unsigned v = 0; !incremental_mode && v < s().num_vars(); ++v) {
             literal lit(v, false);
             if (s().is_external(v) && 
                 m_cnstr_use_list[lit.index()].empty() && 
-                m_cnstr_use_list[(~lit).index()].empty() && 
-                !s().is_assumption(v)) {
+                m_cnstr_use_list[(~lit).index()].empty()) {
                 s().set_non_external(v);
                 ++ext;
             }            
         }
-        // ensure that lemmas use only external variables.
+        // ensure that lemmas use only non-eliminated variables
         for (constraint* cp : m_learned) {
             constraint& c = *cp;
             if (c.was_removed()) continue;
@@ -4182,6 +4185,9 @@ namespace sat {
     bool ba_solver::check_model(model const& m) const {
         bool ok = true;
         for (constraint const* c : m_constraints) {
+            if (c->is_pure() && c->lit() != null_literal && m[c->lit().var()] == (c->lit().sign() ? l_true : l_false)) {
+                continue;
+            }
             switch (eval(m, *c)) {
             case l_false: 
                 IF_VERBOSE(0, verbose_stream() << "failed checking " << c->id() << ": " << *c << "\n";);
diff --git a/src/sat/sat_solver.cpp b/src/sat/sat_solver.cpp
index 4f2752fe6..5c937a5fb 100644
--- a/src/sat/sat_solver.cpp
+++ b/src/sat/sat_solver.cpp
@@ -2358,6 +2358,14 @@ namespace sat {
             idx--;
         }
         reset_unmark(old_size);
+        if (m_core.size() > 1) {
+            unsigned j = 0;
+            for (unsigned i = 0; i < m_core.size(); ++i) {
+                if (lvl(m_core[i]) > 0) m_core[j++] = m_core[i];            
+            }
+            m_core.shrink(j);
+        }
+
         if (m_config.m_core_minimize) {
             if (m_min_core_valid && m_min_core.size() < m_core.size()) {
                 IF_VERBOSE(1, verbose_stream() << "(sat.updating core " << m_min_core.size() << " " << m_core.size() << ")\n";);
diff --git a/src/sat/sat_solver/inc_sat_solver.cpp b/src/sat/sat_solver/inc_sat_solver.cpp
index ed8f48762..4d7325ecb 100644
--- a/src/sat/sat_solver/inc_sat_solver.cpp
+++ b/src/sat/sat_solver/inc_sat_solver.cpp
@@ -18,6 +18,7 @@ Notes:
 --*/
 
 
+#include "util/gparams.h"
 #include "ast/ast_pp.h"
 #include "ast/ast_translation.h"
 #include "ast/ast_util.h"
@@ -584,7 +585,9 @@ private:
     }
 
     bool internalize_var(expr* v, sat::bool_var_vector& bvars) {
-        obj_map<func_decl, expr*> const& const2bits = m_bb_rewriter->const2bits();
+        obj_map<func_decl, expr*> const2bits;
+        ptr_vector<func_decl> newbits;
+        m_bb_rewriter->end_rewrite(const2bits, newbits);
         expr* bv;
         bv_util bvutil(m);
         bool internalized = false;
@@ -803,12 +806,13 @@ private:
         }
         TRACE("sat", model_smt2_pp(tout, m, *mdl, 0););
         
-        // IF_VERBOSE(0, model_smt2_pp(verbose_stream() << "after\n", m, *mdl, 0););
 
-#if 0
-        IF_VERBOSE(0, verbose_streamm() << "Verifying solution\n";);
+        if (!gparams::get().get_bool("model_validate", false)) return;
+        IF_VERBOSE(0, verbose_stream() << "Verifying solution\n";);
         model_evaluator eval(*mdl);
+        eval.set_model_completion(false);
         bool all_true = true;
+        //unsigned i = 0;
         for (expr * f : m_fmls) {
             expr_ref tmp(m);
             eval(f, tmp);
@@ -819,19 +823,21 @@ private:
                 IF_VERBOSE(0, verbose_stream() << "failed to verify: " << mk_pp(f, m) << "\n";);
                 all_true = false;
             }
-            else {
-                VERIFY(m.is_true(tmp));                                
-            }
+            //IF_VERBOSE(0, verbose_stream() << (i++) << ": " << mk_pp(f, m) << "\n");
         }
         if (!all_true) {
-            IF_VERBOSE(0, verbose_stream() << m_params << "\n";);
-            IF_VERBOSE(0, m_sat_mc->display(verbose_stream() << "sat mc\n"););
-            IF_VERBOSE(0, if (m_mcs.back()) m_mcs.back()->display(verbose_stream() << "mc0\n"););
+            IF_VERBOSE(0, verbose_stream() << m_params << "\n");
+            IF_VERBOSE(0, m_sat_mc->display(verbose_stream() << "sat mc\n"));
+            IF_VERBOSE(0, if (m_mcs.back()) m_mcs.back()->display(verbose_stream() << "mc0\n"));
             //IF_VERBOSE(0, m_solver.display(verbose_stream()));
-            IF_VERBOSE(0, for (auto const& kv : m_map) verbose_stream() << mk_pp(kv.m_key, m) << " |-> " << kv.m_value << "\n";);
+            IF_VERBOSE(0, for (auto const& kv : m_map) verbose_stream() << mk_pp(kv.m_key, m) << " |-> " << kv.m_value << "\n");
+        }
+        else {
+            IF_VERBOSE(0, verbose_stream() << "solution verified\n");
+//            IF_VERBOSE(0, if (m_mcs.back()) m_mcs.back()->display(verbose_stream() << "mcs\n"));
+//            IF_VERBOSE(0, if (m_sat_mc) m_sat_mc->display(verbose_stream() << "sat_mc\n"));
+//            IF_VERBOSE(0, model_smt2_pp(verbose_stream() << "after\n", m, *mdl, 0););
         }
-
-#endif
     }
 };
 
diff --git a/src/tactic/bv/bit_blaster_model_converter.cpp b/src/tactic/bv/bit_blaster_model_converter.cpp
index 6ace1300a..785ecb57e 100644
--- a/src/tactic/bv/bit_blaster_model_converter.cpp
+++ b/src/tactic/bv/bit_blaster_model_converter.cpp
@@ -31,10 +31,15 @@ template<bool TO_BOOL>
 struct bit_blaster_model_converter : public model_converter {
     func_decl_ref_vector      m_vars;
     expr_ref_vector           m_bits;
+    func_decl_ref_vector      m_newbits;
 
     ast_manager & m() const { return m_vars.get_manager(); }
     
-    bit_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits):m_vars(m), m_bits(m) {
+    bit_blaster_model_converter(
+        ast_manager & m, 
+        obj_map<func_decl, expr*> const & const2bits, 
+        ptr_vector<func_decl> const& newbits):
+        m_vars(m), m_bits(m), m_newbits(m) {
         for (auto const& kv : const2bits) {
             func_decl * v = kv.m_key;
             expr * bits   = kv.m_value;
@@ -43,6 +48,8 @@ struct bit_blaster_model_converter : public model_converter {
             m_vars.push_back(v);
             m_bits.push_back(bits);
         }
+        for (func_decl* f : newbits) 
+            m_newbits.push_back(f);
     }
     
     virtual ~bit_blaster_model_converter() {
@@ -200,10 +207,11 @@ struct bit_blaster_model_converter : public model_converter {
     }
     
     void display(std::ostream & out) override {
+        for (func_decl * f : m_newbits) 
+            display_del(out, f);
         unsigned sz = m_vars.size();
-        for (unsigned i = 0; i < sz; i++) {
+        for (unsigned i = 0; i < sz; i++) 
             display_add(out, m(), m_vars.get(i), m_bits.get(i));
-        }
     }
 
     void get_units(obj_map<expr, bool>& units) override {
@@ -211,7 +219,7 @@ struct bit_blaster_model_converter : public model_converter {
     }
 
 protected:
-    bit_blaster_model_converter(ast_manager & m):m_vars(m), m_bits(m) { }
+    bit_blaster_model_converter(ast_manager & m):m_vars(m), m_bits(m), m_newbits(m) { }
 public:
 
     model_converter * translate(ast_translation & translator) override {
@@ -220,16 +228,18 @@ public:
             res->m_vars.push_back(translator(v));
         for (expr* b : m_bits)
             res->m_bits.push_back(translator(b));
+        for (func_decl* f : m_newbits)
+            res->m_newbits.push_back(translator(f));
         return res;
     }
 };
 
-model_converter * mk_bit_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits) {
-    return const2bits.empty() ? nullptr : alloc(bit_blaster_model_converter<true>, m, const2bits);
+model_converter * mk_bit_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits, ptr_vector<func_decl> const& newbits) {
+    return const2bits.empty() ? nullptr : alloc(bit_blaster_model_converter<true>, m, const2bits, newbits);
 }
 
-model_converter * mk_bv1_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits) {
-    return const2bits.empty() ? nullptr : alloc(bit_blaster_model_converter<false>, m, const2bits);
+model_converter * mk_bv1_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits, ptr_vector<func_decl> const& newbits) {
+    return const2bits.empty() ? nullptr : alloc(bit_blaster_model_converter<false>, m, const2bits, newbits);
 }
 
 
diff --git a/src/tactic/bv/bit_blaster_model_converter.h b/src/tactic/bv/bit_blaster_model_converter.h
index f7dd254b4..057891ec6 100644
--- a/src/tactic/bv/bit_blaster_model_converter.h
+++ b/src/tactic/bv/bit_blaster_model_converter.h
@@ -21,7 +21,7 @@ Notes:
 
 #include "tactic/model_converter.h"
 
-model_converter * mk_bit_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits);
-model_converter * mk_bv1_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits);
+model_converter * mk_bit_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits, ptr_vector<func_decl> const& newbits);
+model_converter * mk_bv1_blaster_model_converter(ast_manager & m, obj_map<func_decl, expr*> const & const2bits, ptr_vector<func_decl> const& newbits);
 
 #endif
diff --git a/src/tactic/bv/bit_blaster_tactic.cpp b/src/tactic/bv/bit_blaster_tactic.cpp
index 39300b7dc..172768feb 100644
--- a/src/tactic/bv/bit_blaster_tactic.cpp
+++ b/src/tactic/bv/bit_blaster_tactic.cpp
@@ -86,8 +86,9 @@ class bit_blaster_tactic : public tactic {
             
             if (change && g->models_enabled()) {
                 obj_map<func_decl, expr*> const2bits;
-                m_rewriter->end_rewrite(const2bits);
-                g->add(mk_bit_blaster_model_converter(m(), const2bits));
+                ptr_vector<func_decl> newbits;
+                m_rewriter->end_rewrite(const2bits, newbits);
+                g->add(mk_bit_blaster_model_converter(m(), const2bits, newbits));
             }
             g->inc_depth();
             result.push_back(g.get());
diff --git a/src/tactic/bv/bv1_blaster_tactic.cpp b/src/tactic/bv/bv1_blaster_tactic.cpp
index d23d7a308..a34f1eb15 100644
--- a/src/tactic/bv/bv1_blaster_tactic.cpp
+++ b/src/tactic/bv/bv1_blaster_tactic.cpp
@@ -36,6 +36,7 @@ class bv1_blaster_tactic : public tactic {
         ast_manager &                      m_manager;
         bv_util                            m_util;
         obj_map<func_decl, expr*>          m_const2bits;
+        ptr_vector<func_decl>              m_newbits;
         expr_ref_vector                    m_saved;
         expr_ref                           m_bit1;
         expr_ref                           m_bit0;
@@ -107,6 +108,7 @@ class bv1_blaster_tactic : public tactic {
             ptr_buffer<expr> bits;
             for (unsigned i = 0; i < bv_size; i++) {
                 bits.push_back(m().mk_fresh_const(0, b));
+                m_newbits.push_back(to_app(bits.back())->get_decl());
             }
             r = butil().mk_concat(bits.size(), bits.c_ptr());
             m_saved.push_back(r);
@@ -405,7 +407,7 @@ class bv1_blaster_tactic : public tactic {
             }
             
             if (g->models_enabled())
-                g->add(mk_bv1_blaster_model_converter(m(), m_rw.cfg().m_const2bits));
+                g->add(mk_bv1_blaster_model_converter(m(), m_rw.cfg().m_const2bits, m_rw.cfg().m_newbits));
             g->inc_depth();
             result.push_back(g.get());
             m_rw.cfg().cleanup();
diff --git a/src/tactic/core/propagate_values_tactic.cpp b/src/tactic/core/propagate_values_tactic.cpp
index 45ff6250a..3f29005b3 100644
--- a/src/tactic/core/propagate_values_tactic.cpp
+++ b/src/tactic/core/propagate_values_tactic.cpp
@@ -23,6 +23,7 @@ Revision History:
 #include "ast/ast_smt2_pp.h"
 #include "ast/expr_substitution.h"
 #include "tactic/goal_shared_occs.h"
+#include "ast/pb_decl_plugin.h"
 
 class propagate_values_tactic : public tactic {
     struct     imp {
@@ -129,10 +130,23 @@ class propagate_values_tactic : public tactic {
             }
 
             TRACE("shallow_context_simplifier_bug", tout << mk_ismt2_pp(curr, m) << "\n---->\n" << mk_ismt2_pp(new_curr, m) << "\n";);
-            push_result(new_curr, new_pr);
-            
-            if (new_curr != curr)
+            if (new_curr != curr) {
                 m_modified = true;
+                //if (has_pb(curr)) 
+                //    IF_VERBOSE(0, verbose_stream() << mk_ismt2_pp(curr, m) << "\n---->\n" << mk_ismt2_pp(new_curr, m) << "\n");
+            }
+            push_result(new_curr, new_pr);            
+        }
+
+        bool has_pb(expr* e) {
+            pb_util pb(m);
+            if (pb.is_ge(e)) return true;
+            if (m.is_or(e)) {
+                for (expr* a : *to_app(e)) {
+                    if (pb.is_ge(a)) return true;
+                }
+            }
+            return false;
         }
 
         void operator()(goal_ref const & g, 
@@ -206,6 +220,7 @@ class propagate_values_tactic : public tactic {
             SASSERT(m_goal->is_well_sorted());
             TRACE("propagate_values", tout << "end\n"; m_goal->display(tout););
             TRACE("propagate_values_core", m_goal->display_with_dependencies(tout););
+            //IF_VERBOSE(0, m_goal->display(verbose_stream()));
             m_goal = 0;
         }
     };
diff --git a/src/tactic/core/solve_eqs_tactic.cpp b/src/tactic/core/solve_eqs_tactic.cpp
index 5fbf9aaf5..08b771df5 100644
--- a/src/tactic/core/solve_eqs_tactic.cpp
+++ b/src/tactic/core/solve_eqs_tactic.cpp
@@ -23,6 +23,7 @@ Revision History:
 #include "util/cooperate.h"
 #include "tactic/goal_shared_occs.h"
 #include "ast/ast_pp.h"
+#include "ast/pb_decl_plugin.h"
 
 class solve_eqs_tactic : public tactic {
     struct imp {
@@ -347,10 +348,8 @@ class solve_eqs_tactic : public tactic {
             
             TRACE("solve_eqs", 
                   tout << "candidate vars:\n";
-                  ptr_vector<app>::iterator it = m_vars.begin();
-                  ptr_vector<app>::iterator end = m_vars.end();
-                  for (; it != end; ++it) {
-                      tout << mk_ismt2_pp(*it, m()) << " ";
+                  for (app* v : m_vars) {
+                      tout << mk_ismt2_pp(v, m()) << " ";
                   }
                   tout << "\n";);
         }
@@ -492,11 +491,9 @@ class solve_eqs_tactic : public tactic {
             
             TRACE("solve_eqs", 
                   tout << "ordered vars:\n";
-                  ptr_vector<app>::iterator it = m_ordered_vars.begin();
-                  ptr_vector<app>::iterator end = m_ordered_vars.end();
-                  for (; it != end; ++it) {
-                      SASSERT(m_candidate_vars.is_marked(*it));
-                      tout << mk_ismt2_pp(*it, m()) << " ";
+                  for (app* v : m_ordered_vars) {
+                      SASSERT(m_candidate_vars.is_marked(v));
+                      tout << mk_ismt2_pp(v, m()) << " ";
                   }
                   tout << "\n";);
             m_candidate_vars.reset();
@@ -529,8 +526,7 @@ class solve_eqs_tactic : public tactic {
             m_subst->reset();
             TRACE("solve_eqs", 
                   tout << "after normalizing variables\n";
-                  for (unsigned i = 0; i < m_ordered_vars.size(); i++) {
-                      expr * v = m_ordered_vars[i];
+                  for (expr * v : m_ordered_vars) {
                       expr * def = 0;
                       proof * pr = 0;
                       expr_dependency * dep = 0;
@@ -539,16 +535,15 @@ class solve_eqs_tactic : public tactic {
                   });
 #if 0
             DEBUG_CODE({
-                for (unsigned i = 0; i < m_ordered_vars.size(); i++) {
-                    expr * v = m_ordered_vars[i];
-                    expr * def = 0;
-                    proof * pr = 0;
-                    expr_dependency * dep = 0;
-                    m_norm_subst->find(v, def, pr, dep);
-                    SASSERT(def != 0);
-                    CASSERT("solve_eqs_bug", !occurs(v, def));
-                }
-            });
+                    for (expr * v : m_ordered_vars) {
+                        expr * def = 0;
+                        proof * pr = 0;
+                        expr_dependency * dep = 0;
+                        m_norm_subst->find(v, def, pr, dep);
+                        SASSERT(def != 0);
+                        CASSERT("solve_eqs_bug", !occurs(v, def));
+                    }
+                });
 #endif
         }
 
@@ -575,6 +570,13 @@ class solve_eqs_tactic : public tactic {
                 }
 
                 m_r->operator()(f, new_f, new_pr, new_dep);
+#if 0
+                pb_util pb(m());
+                if (pb.is_ge(f) && f != new_f) {
+                    IF_VERBOSE(0, verbose_stream() << mk_ismt2_pp(f, m()) << "\n--->\n" << mk_ismt2_pp(new_f, m()) << "\n");
+                }
+#endif
+
                 TRACE("solve_eqs_subst", tout << mk_ismt2_pp(f, m()) << "\n--->\n" << mk_ismt2_pp(new_f, m()) << "\n";);
                 m_num_steps += m_r->get_num_steps() + 1;
                 if (m_produce_proofs)
@@ -592,12 +594,11 @@ class solve_eqs_tactic : public tactic {
                   g.display(tout););
 #if 0
             DEBUG_CODE({
-                for (unsigned i = 0; i < m_ordered_vars.size(); i++) {
-                    expr * v = m_ordered_vars[i];
-                    for (unsigned j = 0; j < g.size(); j++) {
-                        CASSERT("solve_eqs_bug", !occurs(v, g.form(j)));
-                    }
-                }});
+                    for (expr* v : m_ordered_vars) {
+                        for (unsigned j = 0; j < g.size(); j++) {
+                            CASSERT("solve_eqs_bug", !occurs(v, g.form(j)));
+                        }
+                    }});
 #endif
         }