remove last references to unit clauses

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/math/polysat/clause_builder.cpp

@@ -57,9 +57,11 @@ namespace polysat {
         SASSERT(c);
         SASSERT(c->has_bvar());
         SASSERT(!c.is_always_true());  // clause would be a tautology
+#if 0
         if (c->unit_clause()) {
             return;
         }       
+#endif
         m_literals.push_back(c.blit());
     }
 

src/math/polysat/conflict.cpp

@@ -209,8 +209,6 @@ namespace polysat {
         c_lemma.push(c.blit());
         clause_ref lemma = c_lemma.build();
         cm().store(lemma.get(), s());
-        if (lemma->size() == 1)
-            c->set_unit_clause(lemma.get());
         if (s().m_bvars.value(c.blit()) == l_undef)
             s().assign_bool(s().level(*lemma), c.blit(), lemma.get(), nullptr);
     }

src/math/polysat/constraint.cpp

@@ -263,11 +263,6 @@ namespace polysat {
         narrow(s, is_positive);
     }
 
-    void constraint::set_unit_clause(clause *cl) {
-        // can be seen as a cache... store the lowest-level unit clause for this constraint.
-        if (!cl || !m_unit_clause)
-            m_unit_clause = cl;
-    }
 
     unsigned constraint::level(solver& s) const {
         if (s.m_bvars.value(sat::literal(bvar())) != l_undef)

src/math/polysat/constraint.h

@@ -131,7 +131,6 @@ namespace polysat {
         friend class ule_constraint;
 
         // constraint_manager* m_manager;
-        clause*             m_unit_clause = nullptr;  ///< If this constraint was asserted by a unit clause, we store that clause here.
         ckind_t             m_kind;
         unsigned_vector     m_vars;
         lbool               m_external_sign = l_undef;
@@ -178,9 +177,6 @@ namespace polysat {
         std::string bvar2string() const;
         unsigned level(solver& s) const;
 
-        clause* unit_clause() const { return m_unit_clause; }
-        void set_unit_clause(clause* cl);
-
         void set_external(bool sign) { m_external_sign = to_lbool(sign); }
         void unset_external() { m_external_sign = l_undef; }
         bool is_external() const { return m_external_sign != l_undef; }

src/math/polysat/solver.cpp

@@ -121,18 +121,9 @@ namespace polysat {
             set_conflict(c /*, dep */);
             return;
         }
-#if 0
-        clause_ref unit = clause::from_unit(c);
-        m_constraints.store(unit.get(), *this);
-        c->set_unit_clause(unit.get());
-        (void) dep; // dependencies go into justification
-        assign_bool(m_level, lit, c->unit_clause(), nullptr);
-#else
-        // just add them as axioms, tracked by dependencies
         m_bvars.assign(lit, m_level, nullptr, nullptr, dep);
         m_trail.push_back(trail_instr_t::assign_bool_i);
         m_search.push_boolean(lit);
-#endif
 
 #if ENABLE_LINEAR_SOLVER
         m_linear_solver.new_constraint(*c.get());
@@ -743,14 +734,8 @@ namespace polysat {
             LOG("   Literal " << lit << " is: " << lit2cnstr(lit));
             SASSERT(m_bvars.value(lit) != l_true);
         }
-        if (lemma.empty())
-            std::cout << lemma << "\n";
         SASSERT(!lemma.empty());
         m_constraints.store(&lemma, *this);
-        if (lemma.size() == 1) {
-            signed_constraint c = lit2cnstr(lemma[0]);
-            c->set_unit_clause(&lemma);
-        }
         propagate();
     }