create a conflict explanation

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

src/math/lp/dioph_eq.cpp

@@ -211,7 +211,7 @@ namespace lp {
             init();
             while(m_f.size()) {
                 if (!normalize_by_gcd()) 
-                    return lia_move::unsat;
+                    return lia_move::conflict;
                 rewrite_eqs();
             }
             return lia_move::sat;
@@ -298,11 +298,12 @@ namespace lp {
                 remove_fresh_variables(m_eprime[p.j()].m_e);
             }
             u_dependency* dep = nullptr;
-            for (const auto & p : ep.m_l) {
+            for (const auto & pl : ep.m_l)
-                if (lra.column_is_fixed(p.j()))  {
+                for (const auto & p : m_eprime[pl.j()].m_e)
-                    lra.explain_fixed_column(p.j(), ex);
+                    if (lra.column_is_fixed(p.j()))
-                }
+                        lra.explain_fixed_column(p.j(), ex);
-            }
+            
+            TRACE("dioph_eq", lra.print_expl(tout, ex););
         }
         void remove_fresh_variables(term_o& t) {
             // TODO implement

src/math/lp/dioph_eq.h

@@ -17,6 +17,7 @@ Revision History:
 --*/
 #pragma once
 #include "math/lp/lia_move.h"
+#include "math/lp/explanation.h"
 
 namespace lp {
     

src/math/lp/int_solver.cpp

@@ -168,8 +168,9 @@ namespace lp {
             dioph_eq de(lia);
             lia_move r = de.check();
 
-            if (r == lia_move::unsat) {
+            if (r == lia_move::conflict) {
                 de.explain(*this->m_ex);
+                return lia_move::conflict;
             } else if (r == lia_move::sat)  {
                 NOT_IMPLEMENTED_YET();
             }

src/math/lp/lar_solver.h

@@ -591,6 +591,14 @@ public:
         }
         return dep;
     }
+
+    std::ostream& print_expl(std::ostream& out, const explanation& exp) const {
+        for (auto p : exp)
+            constraints().display(
+                out, [this](lpvar j) { return get_variable_name(j); }, p.ci());
+        return out;
+    }
+
     void explain_fixed_column(unsigned j, explanation& ex);
     u_dependency* join_deps(u_dependency* a, u_dependency *b) { return m_dependencies.mk_join(a, b); }
     inline constraint_set const& constraints() const { return m_constraints; }

src/math/lp/lp_bound_propagator.h

@@ -213,20 +213,13 @@ public:
         m_visited_rows.reset();
     }
 
-    std::ostream& print_expl(std::ostream& out, const explanation& exp) const {
-        for (auto p : exp)
-            lp().constraints().display(
-                out, [this](lpvar j) { return lp().get_variable_name(j); }, p.ci());
-        return out;
-    }
-
     bool add_eq_on_columns(const explanation& exp, lpvar je, lpvar ke, bool is_fixed) {
         lp_assert(je != ke && is_int(je) == is_int(ke));
         lp_assert(ival(je) == ival(ke));
 
         TRACE("eq",
               tout << "reported idx " << je << ", " << ke << "\n";
-              print_expl(tout, exp);
+              lp().print_expl(tout, exp);
               tout << "theory_vars v" << lp().local_to_external(je) << " == v" << lp().local_to_external(ke) << "\n";);
 
         bool added = m_imp.add_eq(je, ke, exp, is_fixed);
@@ -257,7 +250,7 @@ public:
         TRACE("eq", tout << lp().get_row(row) << std::endl);
         for (const auto& c : lp().get_row(row))
             if (lp().column_is_fixed(c.var()))
-                explain_fixed_column(c.var(), ex);
+                lp().explain_fixed_column(c.var(), ex);
     }
 
     unsigned explain_fixed_in_row_and_get_base(unsigned row, explanation& ex) {
@@ -265,7 +258,7 @@ public:
         TRACE("eq", tout << lp().get_row(row) << std::endl);
         for (const auto& c : lp().get_row(row)) {
             if (lp().column_is_fixed(c.var())) {
-                explain_fixed_column(c.var(), ex);
+                lp().explain_fixed_column(c.var(), ex);
             } 
             else if (lp().is_base(c.var())) {
                 base = c.var();
@@ -357,7 +350,7 @@ public:
               );
         explanation ex;  
         explain_fixed_in_row(row_index, ex);
-        explain_fixed_column(j, ex);
+        lp().explain_fixed_column(j, ex);
         add_eq_on_columns(ex, j, v_j, true);
     }