update todos, working on assignment minimization

src/math/polysat/conflict.cpp

@@ -12,21 +12,12 @@ Author:
 
 Notes:
 
- TODO: constraints containing v could be tracked incrementally when constraints are added/removed using an index.
-
  TODO: try a final core reduction step or other core minimization
 
  TODO: If we have e.g. 4x+y=2 and y=0, then we have a conflict no matter the value of x, so we should drop x=? from the core.
        (works currently if x is unassigned; for other cases we would need extra info from constraint::is_currently_false)
-
- TODO: build_lemma:
        note that we may have added too many variables: e.g., y disappears in x*y if x=0
 
- TODO: keep is buggy. The assert 
-                   SASSERT(premise.is_currently_true(s()) || premise.bvalue(s()) == l_true);
-       does not necessarily hold. A saturation premise could be inserted that is a resolvent that evaluates to false
-       and therefore not a current Boolean literal on the search stack.
-
  TODO: revert(pvar v) is too weak. 
        It should apply saturation rules currently only available for propagated values.
 
@@ -46,9 +37,7 @@ Notes:
 namespace polysat {
 
     conflict::conflict(solver& s):s(s) {
-        ex_engines.push_back(alloc(ex_polynomial_superposition));
+        ex_engines.push_back(alloc(ex_polynomial_superposition, s));
-        for (auto* engine : ex_engines)
-            engine->set_solver(s);
         ve_engines.push_back(alloc(ve_reduction));
         inf_engines.push_back(alloc(inf_saturate));
         for (auto* engine : inf_engines)
@@ -77,7 +66,6 @@ namespace polysat {
         m_literals.reset();
         m_vars.reset();
         m_conflict_var = null_var;
-        m_saturation_premises.reset();
         m_bailout = false;
         SASSERT(empty());        
     }
@@ -146,16 +134,17 @@ namespace polysat {
             m_constraints.push_back(c);
     }
 
+
+    // NOTE: maybe we should skip intermediate steps and just collect the leaf premises for c?
+    // Ensure that c is assigned and justified
     void conflict::insert(signed_constraint c, vector<signed_constraint> const& premises) {
         insert(c);
-        // NOTE: maybe we should skip intermediate steps and just collect the leaf premises for c?
         clause_builder c_lemma(s);
         for (auto premise : premises) {
             LOG_H3("premise: " << premise);
             keep(premise);
             SASSERT(premise->has_bvar());
             SASSERT(premise.bvalue(s) == l_true);         
-            // otherwise the propagation doesn't make sense
             c_lemma.push(~premise.blit());
         }
         c_lemma.push(c.blit());
@@ -210,12 +199,12 @@ namespace polysat {
      * insert it (and recursively, its premises) into \Gamma 
      */
     void conflict::keep(signed_constraint c) {
-        if (!c->has_bvar()) {
+        if (c->has_bvar())
-            remove(c);
+            return;
-            cm().ensure_bvar(c.get());
-            insert(c);
-        }
         LOG_H3("keeping: " << c);
+        remove(c);
+        cm().ensure_bvar(c.get());
+        insert(c);        
     }
 
     clause_builder conflict::build_lemma() {

src/math/polysat/conflict.h

@@ -58,8 +58,6 @@ namespace polysat {
         scoped_ptr_vector<variable_elimination_engine> ve_engines;
         scoped_ptr_vector<inference_engine> inf_engines;
 
-        // ptr_addr_map<constraint, vector<signed_constraint>> m_saturation_premises;
-        map<signed_constraint, vector<signed_constraint>, obj_hash<signed_constraint>, default_eq<signed_constraint>> m_saturation_premises;
     public:
         conflict(solver& s);
         ~conflict();

src/math/polysat/constraint.cpp

@@ -121,6 +121,14 @@ namespace polysat {
         return {lookup(lit.var()), lit};
     }
 
+    bool signed_constraint::is_currently_false(solver& s) const { 
+        return get()->is_currently_false(s.assignment(), is_positive());
+    }
+
+    bool signed_constraint::is_currently_true(solver& s) const { 
+        return get()->is_currently_true(s.assignment(), is_positive());
+    }
+
     /** Look up constraint among stored constraints. */
     constraint* constraint_manager::dedup(constraint* c1) {
         constraint* c2 = nullptr;

src/math/polysat/constraint.h

@@ -16,6 +16,7 @@ Author:
 #include "math/polysat/clause.h"
 #include "math/polysat/types.h"
 #include "math/polysat/interval.h"
+#include "math/polysat/search_state.h"
 
 namespace polysat {
 
@@ -161,8 +162,8 @@ namespace polysat {
         bool propagate(solver& s, bool is_positive, pvar v);
         virtual void propagate_core(solver& s, bool is_positive, pvar v, pvar other_v);
         virtual bool is_always_false(bool is_positive) const = 0;
-        virtual bool is_currently_false(solver& s, bool is_positive) const = 0;
+        virtual bool is_currently_false(assignment_t const& a, bool is_positive) const = 0;
-        virtual bool is_currently_true(solver& s, bool is_positive) const = 0;
+        virtual bool is_currently_true(assignment_t const& a, bool is_positive) const = 0;
         virtual void narrow(solver& s, bool is_positive) = 0;
         virtual inequality as_inequality(bool is_positive) const = 0;
 
@@ -220,9 +221,9 @@ namespace polysat {
         bool propagate(solver& s, pvar v) { return get()->propagate(s, is_positive(), v); }
         void propagate_core(solver& s, pvar v, pvar other_v) { get()->propagate_core(s, is_positive(), v, other_v); }
         bool is_always_false() const { return get()->is_always_false(is_positive()); }
-        bool is_always_true() const { return get()->is_always_false(is_negative()); }
+        bool is_always_true() const { return get()->is_always_false(is_negative()); }        
-        bool is_currently_false(solver& s) const { return get()->is_currently_false(s, is_positive()); }
+        bool is_currently_false(solver& s) const;
-        bool is_currently_true(solver& s) const { return get()->is_currently_true(s, is_positive()); }
+        bool is_currently_true(solver& s) const;
         lbool bvalue(solver& s) const;
         unsigned level(solver& s) const { return get()->level(s); }
         void narrow(solver& s) { get()->narrow(s, is_positive()); }

src/math/polysat/explain.cpp

@@ -19,8 +19,8 @@ namespace polysat {
 
     signed_constraint ex_polynomial_superposition::resolve1(pvar v, signed_constraint c1, signed_constraint c2) {
         // c1 is true, c2 is false
-        SASSERT(c1.is_currently_true(s()));
+        SASSERT(c1.is_currently_true(s));
-        SASSERT(c2.is_currently_false(s()));
+        SASSERT(c2.is_currently_false(s));
         LOG_H3("Resolving upon v" << v);
         LOG("c1: " << c1);
         LOG("c2: " << c2);
@@ -33,9 +33,9 @@ namespace polysat {
         // (this condition might be too strict, but we use it for now to prevent looping)
         if (b.degree(v) <= r.degree(v))
             return {};
-        signed_constraint c = s().eq(r);
+        signed_constraint c = s.eq(r);
-        LOG("resolved: " << c << "        currently false? " << c.is_currently_false(s()));
+        LOG("resolved: " << c << "        currently false? " << c.is_currently_false(s));
-        if (!c.is_currently_false(s()))
+        if (!c.is_currently_false(s))
             return {};
         return c;
     }
@@ -51,15 +51,15 @@ namespace polysat {
         for (auto c1 : core) {
             if (!is_positive_equality_over(v, c1))
                 continue;
-            if (!c1.is_currently_true(s()))
+            if (!c1.is_currently_true(s))
                 continue;
             signed_constraint c = resolve1(v, c1, c2);
             if (!c)
                 continue;
             if (!c->has_bvar())
-                s().m_constraints.ensure_bvar(c.get());
+                s.m_constraints.ensure_bvar(c.get());
 
-            switch (c.bvalue(s())) {
+            switch (c.bvalue(s)) {
             case l_false:
                 // new conflict state based on propagation and theory conflict
                 core.reset();
@@ -72,8 +72,8 @@ namespace polysat {
                 premises.push_back(c1);
                 premises.push_back(c2);
                 core.replace(c2, c, premises);
-                SASSERT(l_true == c.bvalue(s()));
+                SASSERT(l_true == c.bvalue(s));
-                SASSERT(c.is_currently_false(s()));
+                SASSERT(c.is_currently_false(s));
                 break;
             default:
                 break;
@@ -95,7 +95,7 @@ namespace polysat {
         for (auto c2 : core) {
             if (!is_positive_equality_over(v, c2))
                 continue;
-            if (!c2.is_currently_false(s()))
+            if (!c2.is_currently_false(s))
                 continue;
             switch (find_replacement(c2, v, core)) {
             case l_undef:
@@ -115,7 +115,7 @@ namespace polysat {
         while (progress) {
             progress = false;
             for (auto c : core) {
-                if (is_positive_equality_over(v, c) && c.is_currently_true(s()) && reduce_by(v, c, core)) {
+                if (is_positive_equality_over(v, c) && c.is_currently_true(s) && reduce_by(v, c, core)) {
                     progress = true;
                     break;
                 }
@@ -130,7 +130,7 @@ namespace polysat {
                 continue;
             if (is_positive_equality_over(v, c))
                 continue;
-            if (!c.is_currently_false(s()))
+            if (!c.is_currently_false(s))
                 continue;
             if (c->is_ule()) {
                 auto lhs = c->to_ule().lhs();
@@ -139,14 +139,14 @@ namespace polysat {
                 auto b = rhs.reduce(v, p);
                 if (a == lhs && b == rhs)
                     continue;
-                auto c2 = s().ule(a, b);
+                auto c2 = s.ule(a, b);
                 if (!c.is_positive())
                     c2 = ~c2;
-                SASSERT(c2.is_currently_false(s()));                
+                SASSERT(c2.is_currently_false(s));                
-                if (!c2->has_bvar() || l_undef == c2.bvalue(s()))
+                if (!c2->has_bvar() || l_undef == c2.bvalue(s))
                     core.keep(c2);  // adds propagation of c to the search stack
                 core.reset();
-                if (c2.bvalue(s()) == l_false) {
+                if (c2.bvalue(s) == l_false) {
                     core.insert(eq);
                     core.insert(c);
                     core.insert(~c2);

src/math/polysat/explain.h

@@ -23,11 +23,10 @@ namespace polysat {
 
     class explainer {
         friend class conflict;
-        solver* m_solver = nullptr;
-        void set_solver(solver& s) { m_solver = &s; }
     protected:
-        solver& s() { return *m_solver; }
+        solver& s;
     public:
+        explainer(solver& s) :s(s) {}
         virtual ~explainer() {}
         virtual bool try_explain(pvar v, /* vector<signed_constraint> const& cjust_v, */ conflict& core) = 0;
     };
@@ -41,6 +40,7 @@ namespace polysat {
         bool reduce_by(pvar, signed_constraint c, conflict& core);
         lbool try_explain1(pvar v, conflict& core);
     public:
+        ex_polynomial_superposition(solver& s) : explainer(s) {}
         bool try_explain(pvar v, conflict& core) override;
     };
 

src/math/polysat/ule_constraint.cpp

@@ -204,15 +204,15 @@ namespace polysat {
         return is_always_false(is_positive, lhs(), rhs());
     }
 
-    bool ule_constraint::is_currently_false(solver& s, bool is_positive) const {
+    bool ule_constraint::is_currently_false(assignment_t const& a, bool is_positive) const {
-        auto p = lhs().subst_val(s.assignment());
+        auto p = lhs().subst_val(a);
-        auto q = rhs().subst_val(s.assignment());
+        auto q = rhs().subst_val(a);
         return is_always_false(is_positive, p, q);
     }
 
-    bool ule_constraint::is_currently_true(solver& s, bool is_positive) const {
+    bool ule_constraint::is_currently_true(assignment_t const& a, bool is_positive) const {
-        auto p = lhs().subst_val(s.assignment());
+        auto p = lhs().subst_val(a);
-        auto q = rhs().subst_val(s.assignment());
+        auto q = rhs().subst_val(a);
         if (is_positive) {
             if (p.is_zero())
                 return true;

src/math/polysat/ule_constraint.h

@@ -34,8 +34,8 @@ namespace polysat {
         std::ostream& display(std::ostream& out) const override;
         bool is_always_false(bool is_positive, pdd const& lhs, pdd const& rhs) const;
         bool is_always_false(bool is_positive) const override;
-        bool is_currently_false(solver& s, bool is_positive) const override;
+        bool is_currently_false(assignment_t const& a, bool is_positive) const override;
-        bool is_currently_true(solver& s, bool is_positive) const override;
+        bool is_currently_true(assignment_t const& a, bool is_positive) const override;
         void narrow(solver& s, bool is_positive) override;
         inequality as_inequality(bool is_positive) const override;
         unsigned hash() const override;