Connect conflict2

src/math/polysat/CMakeLists.txt

@@ -4,10 +4,9 @@ z3_add_component(polysat
     clause.cpp
     clause_builder.cpp
     conflict.cpp
-    conflict2.cpp
     constraint.cpp
-    eq_explain.cpp
+    # eq_explain.cpp
-    explain.cpp
+    # explain.cpp
     forbidden_intervals.cpp
     inference_logger.cpp
     justification.cpp
@@ -15,7 +14,7 @@ z3_add_component(polysat
     log.cpp
     op_constraint.cpp
     restart.cpp
-    saturation.cpp
+    # saturation.cpp
     search_state.cpp
     simplify.cpp
     simplify_clause.cpp
@@ -23,7 +22,7 @@ z3_add_component(polysat
     solver.cpp
     ule_constraint.cpp
     umul_ovfl_constraint.cpp
-    variable_elimination.cpp
+    # variable_elimination.cpp
     viable.cpp
   COMPONENT_DEPENDENCIES
     util

src/math/polysat/conflict.cpp

@@ -14,7 +14,8 @@ Notes:
 
 --*/
 
-#include "math/polysat/conflict2.h"
+#include "math/polysat/conflict.h"
+#include "math/polysat/clause_builder.h"
 #include "math/polysat/solver.h"
 #include "math/polysat/inference_logger.h"
 #include "math/polysat/log.h"
@@ -25,10 +26,17 @@ Notes:
 #include "math/polysat/saturation.h"
 #include "math/polysat/variable_elimination.h"
 #include <algorithm>
-#include <fstream>
 
 namespace polysat {
 
+    class header_with_var : public displayable {
+        char const* m_text;
+        pvar m_var;
+    public:
+        header_with_var(char const* text, pvar var) : m_text(text), m_var(var) { SASSERT(text); }
+        std::ostream& display(std::ostream& out) const override { return out << m_text << m_var; }
+    };
+
     struct inf_resolve_bool : public inference {
         sat::literal m_lit;
         clause const& m_clause;
@@ -61,7 +69,7 @@ namespace polysat {
         }
     };
 
-    conflict2::conflict2(solver& s) : s(s) {
+    conflict::conflict(solver& s) : s(s) {
         // TODO: m_log_conflicts is always false even if "polysat.log_conflicts=true" is given on the command line
         if (true || s.get_config().m_log_conflicts)
             m_logger = alloc(file_inference_logger, s);
@@ -69,35 +77,73 @@ namespace polysat {
             m_logger = alloc(dummy_inference_logger);
     }
 
-    inference_logger& conflict2::logger() {
+    inference_logger& conflict::logger() {
         return *m_logger;
     }
 
-    bool conflict2::empty() const {
+    conflict::const_iterator conflict::begin() const {
-        return m_literals.empty() && m_vars.empty() && m_lemmas.empty();
+        return conflict_iterator::begin(s.m_constraints, m_literals);
     }
 
-    void conflict2::reset() {
+    conflict::const_iterator conflict::end() const {
+        return conflict_iterator::end(s.m_constraints, m_literals);
+    }
+
+    bool conflict::empty() const {
+        return m_literals.empty()
+            && m_vars.empty()
+            && m_bail_vars.empty()
+            && m_lemmas.empty();
+    }
+
+    void conflict::reset() {
         m_literals.reset();
         m_vars.reset();
+        m_bail_vars.reset();
+        m_relevant_vars.reset();
         m_var_occurrences.reset();
         m_lemmas.reset();
-        m_kind = conflict2_kind_t::ok;
+        m_kind = conflict_kind_t::ok;
         SASSERT(empty());
     }
 
-    void conflict2::set_bailout() {
+    void conflict::set_bailout() {
-        SASSERT(m_kind == conflict2_kind_t::ok);
+        SASSERT(m_kind == conflict_kind_t::ok);
-        m_kind = conflict2_kind_t::bailout;
+        m_kind = conflict_kind_t::bailout;
         s.m_stats.m_num_bailouts++;
     }
 
-    void conflict2::set_backjump() {
+    void conflict::set_backtrack() {
-        SASSERT(m_kind == conflict2_kind_t::ok);
+        SASSERT(m_kind == conflict_kind_t::ok);
-        m_kind = conflict2_kind_t::backjump;
+        SASSERT(m_relevant_vars.empty());
+        m_kind = conflict_kind_t::backtrack;
+
+    }
+    void conflict::set_backjump() {
+        SASSERT(m_kind == conflict_kind_t::ok);
+        m_kind = conflict_kind_t::backjump;
     }
 
-    void conflict2::init(signed_constraint c) {
+    bool conflict::is_relevant_pvar(pvar v) const {
+        switch (m_kind) {
+        case conflict_kind_t::ok:
+            return contains_pvar(v);
+        case conflict_kind_t::bailout:
+            return true;
+        case conflict_kind_t::backtrack:
+            return pvar_occurs_in_constraints(v) || m_relevant_vars.contains(v);
+            // return m_relevant_vars.contains(v);
+        case conflict_kind_t::backjump:
+            UNREACHABLE();  // we don't follow the regular loop when backjumping
+            return false;
+        }
+    }
+
+    bool conflict::is_relevant(sat::literal lit) const {
+        return contains(lit) || contains(~lit);
+    }
+
+    void conflict::init(signed_constraint c) {
         SASSERT(empty());
         if (c.bvalue(s) == l_false) {
             // boolean conflict
@@ -110,34 +156,48 @@ namespace polysat {
             insert_vars(c);
         }
         SASSERT(!empty());
+        logger().begin_conflict();  // TODO: we often call reset/set so doing this here doesn't really work... make subsequent begins a no-op? or separate init and set? (set could then do reset() internally ... and we only need set() for signed_constraint, not all three variations)
+    }
+
+    void conflict::init(clause const& cl) {
+        // if (!empty())
+        //     return;
+        // LOG("Conflict: " << cl);
+        SASSERT(empty());
+        for (auto lit : cl) {
+            auto c = s.lit2cnstr(lit);
+            SASSERT(c.bvalue(s) == l_false);
+            insert(~c);
+        }
+        SASSERT(!empty());
         logger().begin_conflict();
     }
 
-    void conflict2::init(pvar v, bool by_viable_fallback) {
+    void conflict::init(pvar v, bool by_viable_fallback) {
         if (by_viable_fallback) {
+            logger().begin_conflict(header_with_var("unsat core from viable fallback for v", v));
             // Conflict detected by viable fallback:
             // initial conflict is the unsat core of the univariate solver
             signed_constraints unsat_core = s.m_viable_fallback.unsat_core(v);
             for (auto c : unsat_core)
                 insert(c);
-            logger().begin_conflict("unsat core from viable fallback");
             // TODO: apply conflict resolution plugins here too?
         } else {
+            logger().begin_conflict(header_with_var("forbidden interval lemma for v", v));
+            set_backtrack();
             VERIFY(s.m_viable.resolve(v, *this));
             // TODO: in general the forbidden interval lemma is not asserting.
             //       but each branch exclude the current assignment.
             //       in those cases we will (additionally?) need an abstraction that is asserting to make sure viable is updated properly.
-            set_backjump();
-            logger().begin_conflict("forbidden interval lemma");
         }
     }
 
-    bool conflict2::contains(sat::literal lit) const {
+    bool conflict::contains(sat::literal lit) const {
         SASSERT(lit != sat::null_literal);
         return m_literals.contains(lit.index());
     }
 
-    void conflict2::insert(signed_constraint c) {
+    void conflict::insert(signed_constraint c) {
         if (contains(c))
             return;
         if (c.is_always_true())
@@ -153,7 +213,7 @@ namespace polysat {
         }
     }
 
-    void conflict2::insert_eval(signed_constraint c) {
+    void conflict::insert_eval(signed_constraint c) {
         switch (c.bvalue(s)) {
         case l_undef:
             s.assign_eval(c.blit());
@@ -166,20 +226,20 @@ namespace polysat {
         insert(c);
     }
 
-    void conflict2::insert_vars(signed_constraint c) {
+    void conflict::insert_vars(signed_constraint c) {
         for (pvar v : c->vars())
             if (s.is_assigned(v))
                 m_vars.insert(v);
     }
 
-    void conflict2::remove(signed_constraint c) {
+    void conflict::remove(signed_constraint c) {
         SASSERT(contains(c));
         m_literals.remove(c.blit().index());
         for (pvar v : c->vars())
             m_var_occurrences[v]--;
     }
 
-    void conflict2::resolve_bool(sat::literal lit, clause const& cl) {
+    void conflict::resolve_bool(sat::literal lit, clause const& cl) {
         // Note: core: x, y, z; corresponds to clause ~x \/ ~y \/ ~z
         //       clause: x \/ u \/ v
         //       resolvent: ~y \/ ~z \/ u \/ v; as core: y, z, ~u, ~v
@@ -197,7 +257,7 @@ namespace polysat {
         logger().log(inf_resolve_bool(lit, cl));
     }
 
-    void conflict2::resolve_with_assignment(sat::literal lit) {
+    void conflict::resolve_with_assignment(sat::literal lit) {
         // The reason for lit is conceptually:
         //    x1 = v1 /\ ... /\ xn = vn ==> lit
 
@@ -227,19 +287,21 @@ namespace polysat {
         logger().log(inf_resolve_with_assignment(s, lit, c));
     }
 
-    bool conflict2::resolve_value(pvar v) {
+    bool conflict::resolve_value(pvar v) {
-        SASSERT(contains_pvar(v));
-
-        if (is_backjumping()) {
-            for (auto const& c : s.m_viable.get_constraints(v))
-                for (pvar v : c->vars())
-                    logger().log_var(v);
-            return false;
-        }
 
         if (is_bailout())
             return false;
 
+        if (is_backtracking()) {
+            for (auto const& c : s.m_viable.get_constraints(v))
+                for (pvar v : c->vars()) {
+                    m_relevant_vars.insert(v);
+                    logger().log_var(v);
+                }
+            return false;
+        }
+
+        SASSERT(contains_pvar(v));
         auto const& j = s.m_justification[v];
 
         if (j.is_decision() && m_bail_vars.contains(v))   // TODO: what if also m_vars.contains(v)? might have a chance at elimination
@@ -265,12 +327,79 @@ namespace polysat {
         // Need to keep the variable in case of decision
         if (s.is_assigned(v) && j.is_decision())
             m_vars.insert(v);
-        logger().log("bailout");
+        logger().log("Bailout");
         return false;
     }
 
-    std::ostream& conflict2::display(std::ostream& out) const {
+    clause_ref conflict::build_lemma() {
-        out << "TODO\n";
+        LOG_H3("Build lemma from core");
+        LOG("core: " << *this);
+        clause_builder lemma(s);
+
+        // TODO: is this sound, doing it for each constraint separately?
+        // for (auto c : *this)
+        //     minimize_vars(c);
+
+        for (auto c : *this)
+            lemma.push(~c);
+
+        for (unsigned v : m_vars) {
+            auto eq = s.eq(s.var(v), s.get_value(v));
+            if (eq.bvalue(s) == l_undef)
+                s.assign_eval(eq.blit());
+            lemma.push(~eq);
+        }
+        s.decay_activity();
+
+        logger().log_lemma(lemma);
+        logger().end_conflict();
+
+        return lemma.build();
+    }
+
+    bool conflict::minimize_vars(signed_constraint c) {
+        if (m_vars.empty())
+            return false;
+        if (!c.is_currently_false(s))
+            return false;
+
+        assignment_t a;
+        for (auto v : m_vars)
+            a.push_back(std::make_pair(v, s.get_value(v)));
+        for (unsigned i = 0; i < a.size(); ++i) {
+            std::pair<pvar, rational> save = a[i];
+            std::pair<pvar, rational> last = a.back();
+            a[i] = last;
+            a.pop_back();
+            if (c.is_currently_false(s, a))
+                --i;
+            else {
+                a.push_back(last);
+                a[i] = save;
+            }
+        }
+        if (a.size() == m_vars.num_elems())
+            return false;
+        m_vars.reset();
+        for (auto const& [v, val] : a)
+            m_vars.insert(v);
+        logger().log("minimize vars");
+        LOG("reduced " << m_vars);
+        return true;
+    }
+
+    std::ostream& conflict::display(std::ostream& out) const {
+        char const* sep = "";
+        for (auto c : *this)
+            out << sep << c->bvar2string() << " " << c, sep = " ; ";
+        if (!m_vars.empty())
+            out << " vars";
+        for (auto v : m_vars)
+            out << " v" << v;
+        if (!m_bail_vars.empty())
+            out << " bail vars";
+        for (auto v : m_bail_vars)
+            out << " v" << v;
         return out;
     }
 }

src/math/polysat/conflict.h

@@ -77,42 +77,54 @@ TODO:
     - bailout lemma if no method applies (log these cases in particular because it indicates where we are missing something)
     - force a restart if we get a bailout lemma or non-asserting conflict?
 - consider case if v is both in vars and bail_vars (do we need to keep it in bail_vars even if we can eliminate it from vars?)
+- Find a way to use resolve_value with forbidden interval lemmas.
+  Then get rid of conflict_kind_t::backtrack and m_relevant_vars.
+  Maybe:
+    x := a, y := b, z has no viable value
+    - assume y was propagated
+    - FI-Lemma C1 \/ ... \/ Cn without z.
+    - for each i, we should have x := a /\ Ci ==> y != b
+    - can we choose one of the Ci to cover the domain of y and extract an FI-Lemma D1 \/ ... \/ Dk without y,z?
+    - or try to find an L(x,y) such that C1 -> L, ..., Cn -> L, and L -> y != b  (under x := a); worst case y != b can work as L
+- minimize_vars... is it sound to do for each constraint separately, like we are doing now?
 
 
 --*/
 #pragma once
 #include "math/polysat/constraint.h"
-#include "math/polysat/clause_builder.h"
 #include "math/polysat/inference_logger.h"
 #include <optional>
 
 namespace polysat {
 
     class solver;
-    class explainer;
-    class inference_engine;
-    class variable_elimination_engine;
     class conflict_iterator;
-    class inference_logger;
 
-    enum class conflict2_kind_t {
+    enum class conflict_kind_t {
         // standard conflict resolution
         ok,
         // bailout lemma because no appropriate conflict resolution method applies
         bailout,
+        // conflict contains the final lemma;
+        // backtrack to and revert the last relevant decision
+        // NOTE: this is currently used for the forbidden intervals lemmas.
+        //       we should find a way to use resolve_value with these lemmas,
+        //       to properly eliminate value propagations. (see todo notes above)
+        backtrack,
+        // conflict contains the final lemma;
         // force backjumping without further conflict resolution because a good lemma has been found
-        // TODO: distinguish backtrack/revert of last decision from backjump to second-highest level in the lemma
         backjump,
     };
 
-    class conflict2 {
+    class conflict {
         solver& s;
         scoped_ptr<inference_logger> m_logger;
 
         // current conflict core consists of m_literals and m_vars
         indexed_uint_set m_literals;        // set of boolean literals in the conflict
         uint_set m_vars;                    // variable assignments used as premises, shorthand for literals (x := v)
-        uint_set m_bail_vars;               // tracked for cone of influence but not directly involved in conflict resolution
+        uint_set m_bail_vars;               // decision variables that are only used to evaluate a constraint; see resolve_with_assignment.
+        uint_set m_relevant_vars;           // tracked for cone of influence but not directly involved in conflict resolution
 
         unsigned_vector m_var_occurrences;  // for each variable, the number of constraints in m_literals that contain it
 
@@ -120,31 +132,47 @@ namespace polysat {
         // TODO: we might not need all of these in the end. add only the side lemmas which justify a constraint in the final lemma (recursively)?
         vector<clause_ref> m_lemmas;
 
-        conflict2_kind_t m_kind = conflict2_kind_t::ok;
+        conflict_kind_t m_kind = conflict_kind_t::ok;
+
+        bool minimize_vars(signed_constraint c);
 
     public:
-        conflict2(solver& s);
+        conflict(solver& s);
 
         inference_logger& logger();
 
         bool empty() const;
         void reset();
 
-        uint_set const& vars() const { return m_vars; }
+        using const_iterator = conflict_iterator;
+        const_iterator begin() const;
+        const_iterator end() const;
 
-        bool is_bailout() const { return m_kind == conflict2_kind_t::bailout; }
+        uint_set const& vars() const { return m_vars; }
-        bool is_backjumping() const { return m_kind == conflict2_kind_t::backjump; }
+        uint_set const& bail_vars() const { return m_bail_vars; }
+
+        conflict_kind_t kind() const { return m_kind; }
+        bool is_bailout() const { return m_kind == conflict_kind_t::bailout; }
+        bool is_backtracking() const { return m_kind == conflict_kind_t::backtrack; }
+        bool is_backjumping() const { return m_kind == conflict_kind_t::backjump; }
         void set_bailout();
+        void set_backtrack();
         void set_backjump();
 
+        bool is_relevant_pvar(pvar v) const;
+        bool is_relevant(sat::literal lit) const;
+
         /** conflict because the constraint c is false under current variable assignment */
         void init(signed_constraint c);
+        /** boolean conflict with the given clause */
+        void init(clause const& cl);
         /** conflict because there is no viable value for the variable v */
-        void init(pvar v, bool by_viable_fallback = false);
+        void init(pvar v, bool by_viable_fallback);
 
         bool contains(signed_constraint c) const { SASSERT(c); return contains(c.blit()); }
         bool contains(sat::literal lit) const;
         bool contains_pvar(pvar v) const { return m_vars.contains(v) || m_bail_vars.contains(v); }
+        bool pvar_occurs_in_constraints(pvar v) const { return v < m_var_occurrences.size() && m_var_occurrences[v] > 0; }
 
         /**
          * Insert constraint c into conflict state.
@@ -172,9 +200,53 @@ namespace polysat {
         /** Perform resolution with "v = value <- ..." */
         bool resolve_value(pvar v);
 
+        /** Convert the core into a lemma to be learned. */
+        clause_ref build_lemma();
+
         std::ostream& display(std::ostream& out) const;
     };
 
-    inline std::ostream& operator<<(std::ostream& out, conflict2 const& c) { return c.display(out); }
+    inline std::ostream& operator<<(std::ostream& out, conflict const& c) { return c.display(out); }
 
+    class conflict_iterator {
+        friend class conflict;
+
+        using inner_t = indexed_uint_set::iterator;
+
+        constraint_manager* m_cm;
+        inner_t m_inner;
+
+        conflict_iterator(constraint_manager& cm, inner_t inner):
+            m_cm(&cm), m_inner(inner) {}
+
+        static conflict_iterator begin(constraint_manager& cm, indexed_uint_set const& lits) {
+            return {cm, lits.begin()};
+        }
+
+        static conflict_iterator end(constraint_manager& cm, indexed_uint_set const& lits) {
+            return {cm, lits.end()};
+        }
+
+    public:
+        using value_type = signed_constraint;
+        using difference_type = unsigned;
+        using pointer = signed_constraint const*;
+        using reference = signed_constraint const&;
+        using iterator_category = std::input_iterator_tag;
+
+        conflict_iterator& operator++() {
+            ++m_inner;
+            return *this;
+        }
+
+        signed_constraint operator*() const {
+            return m_cm->lookup(sat::to_literal(*m_inner));
+        }
+
+        bool operator==(conflict_iterator const& other) const {
+            return m_inner == other.m_inner;
+        }
+
+        bool operator!=(conflict_iterator const& other) const { return !operator==(other); }
+    };
 }

src/math/polysat/inference_logger.cpp

@@ -40,48 +40,53 @@ namespace polysat {
         return std::string(70, '-');
     }
 
-    void file_inference_logger::begin_conflict(char const* text) {
+    void file_inference_logger::begin_conflict(displayable const& header) {
         ++m_num_conflicts;
-        if (text)
+        LOG("Begin CONFLICT #" << m_num_conflicts << ": " << header);
-            LOG("Begin CONFLICT #" << m_num_conflicts << " (" << text << ")");
-        else
-            LOG("Begin CONFLICT #" << m_num_conflicts);
         m_used_constraints.reset();
         m_used_vars.reset();
         if (!m_out)
             m_out = alloc(std::ofstream, "conflicts.txt");
         else
             out() << "\n\n\n\n\n\n\n\n\n\n\n\n";
-        out() << "CONFLICT #" << m_num_conflicts;
+        out() << "CONFLICT #" << m_num_conflicts << ": " << header << "\n";
-        if (text)
-            out() << " (" << text << ")";
-        out() << "\n";
         // log initial conflict state
         out() << hline() << "\n";
         log_conflict_state();
     }
 
     void file_inference_logger::log_conflict_state() {
-        out() << "TODO";
+        conflict const& core = s.m_conflict;
-        /* TODO: update for new conflict
-        conflict2 const& core = s.m_conflict2;
         for (auto const& c : core) {
-            out_indent() << c.blit() << ": " << c << '\n';
+            sat::literal const lit = c.blit();
-            m_used_constraints.insert(c.blit().index());
+            out_indent() << lit << ": " << c << '\n';
+            // TODO: if justified by a side lemma, print it here
+            // out_indent() << "    justified by: " << lemma << '\n';
+            m_used_constraints.insert(lit.index());
             for (pvar v : c->vars())
                 m_used_vars.insert(v);
         }
         for (auto v : core.vars()) {
-            out_indent() << assignment_pp(core.s, v, core.s.get_value(v)) << "\n";
+            out_indent() << assignment_pp(s, v, s.get_value(v)) << "\n";
             m_used_vars.insert(v);
         }
         for (auto v : core.bail_vars()) {
-            out_indent() << assignment_pp(core.s, v, core.s.get_value(v)) << " (bail)\n";
+            out_indent() << assignment_pp(s, v, s.get_value(v)) << " (bail)\n";
             m_used_vars.insert(v);
         }
-        if (core.is_bailout())
+        switch (core.kind()) {
+        case conflict_kind_t::ok:
+            break;
+        case conflict_kind_t::bailout:
             out_indent() << "(bailout)\n";
-        */
+            break;
+        case conflict_kind_t::backtrack:
+            out_indent() << "(backtrack)\n";
+            break;
+        case conflict_kind_t::backjump:
+            out_indent() << "(backjump)\n";
+            break;
+        }
         out().flush();
     }
 
@@ -102,7 +107,6 @@ namespace polysat {
         out() << "\n";
         for (auto const& lit : cb)
             out_indent() << lit_pp(s, lit) << "\n";
-            // out_indent() << lit << ": " << s.lit2cnstr(lit) << "\n";
         out().flush();
     }
 

src/math/polysat/inference_logger.h

@@ -26,13 +26,26 @@ namespace polysat {
     class search_item;
     class solver;
 
-    class inference {
+    class displayable {
     public:
-        virtual ~inference() {}
+        virtual ~displayable() {}
         virtual std::ostream& display(std::ostream& out) const = 0;
     };
 
-    inline std::ostream& operator<<(std::ostream& out, inference const& i) { return i.display(out); }
+    inline std::ostream& operator<<(std::ostream& out, displayable const& d) { return d.display(out); }
+
+    class display_c_str : public displayable {
+        char const* m_str;
+    public:
+        display_c_str(char const* str) : m_str(str) { }
+        std::ostream& display(std::ostream& out) const override {
+            if (m_str)
+                out << m_str;
+            return out;
+        }
+    };
+
+    class inference : public displayable { };
 
     class inference_named : public inference {
         char const* m_name;
@@ -46,12 +59,14 @@ namespace polysat {
         virtual ~inference_logger() {}
 
         /// Begin next conflict
-        virtual void begin_conflict(char const* text = nullptr) = 0;
+        void begin_conflict(char const* text = nullptr) { begin_conflict(display_c_str(text)); }
+        virtual void begin_conflict(displayable const& header) = 0;
         /// Log inference and the current state.
         virtual void log(inference const& inf) = 0;
         virtual void log(char const* name) { log(inference_named(name)); }
         virtual void log_var(pvar v) = 0;
         /// Log relevant part of search state and viable.
+        /// Call end_conflict before backjumping in the solver.
         virtual void end_conflict() = 0;
 
         /// Log current conflict state (implicitly done by log_inference)
@@ -62,7 +77,7 @@ namespace polysat {
 
     class dummy_inference_logger : public inference_logger {
     public:
-        virtual void begin_conflict(char const* text) override {}
+        virtual void begin_conflict(displayable const& header) override {}
         virtual void log(inference const& inf) override {}
         virtual void log_var(pvar v) override {}
         virtual void end_conflict() override {}
@@ -85,18 +100,11 @@ namespace polysat {
 
     public:
         file_inference_logger(solver& s);
-
+        void begin_conflict(displayable const& header) override;
-        /// Begin next conflict
-        void begin_conflict(char const* text) override;
-        /// Log inference and the current state.
         void log(inference const& inf) override;
         void log_var(pvar v) override;
-        /// Log relevant part of search state and viable.
         void end_conflict() override;
-
-        /// Log current conflict state (implicitly done by log_inference)
         void log_conflict_state() override;
-
         void log_lemma(clause_builder const& cb) override;
     };
 

src/math/polysat/solver.cpp

@@ -33,7 +33,6 @@ namespace polysat {
         m_viable_fallback(*this),
         m_linear_solver(*this),
         m_conflict(*this),
-        m_conflict2(*this),
         m_simplify_clause(*this),
         m_simplify(*this),
         m_restart(*this),
@@ -545,7 +544,7 @@ namespace polysat {
             //       (fail here in debug mode so we notice if we miss some)
             DEBUG_CODE( UNREACHABLE(); );
             m_free_pvars.unassign_var_eh(v);
-            set_conflict(v);
+            set_conflict(v, false);
             return;
         case dd::find_t::singleton:
             // NOTE: this case may happen legitimately if all other possibilities were excluded by brute force search
@@ -578,8 +577,7 @@ namespace polysat {
             case dd::find_t::empty:
                 LOG("Fallback solver: unsat");
                 m_free_pvars.unassign_var_eh(v);
-                auto core = m_viable_fallback.unsat_core(v);  // TODO: add constraints from unsat_core to conflict
+                set_conflict(v, true);
-                set_conflict(v);
                 return;
             }
         }
@@ -620,17 +618,6 @@ namespace polysat {
 
         SASSERT(is_conflict());
 
-        if (m_conflict.conflict_var() != null_var) {
-            m_conflict.begin_conflict("backtrack_fi");
-            pvar v = m_conflict.conflict_var();
-            // This case corresponds to a propagation of conflict_var, except it's not explicitly on the stack.
-            // TODO: use unsat core from m_viable_fallback if the conflict is from there
-            VERIFY(m_viable.resolve(v, m_conflict));
-            backtrack_fi();
-            return;
-        }
-        m_conflict.begin_conflict("resolve_conflict");
-
         search_iterator search_it(m_search);
         while (search_it.next()) {
             auto& item = *search_it;
@@ -638,23 +625,21 @@ namespace polysat {
             if (item.is_assignment()) {
                 // Resolve over variable assignment
                 pvar v = item.var();
-                if (!m_conflict.contains_pvar(v) && !m_conflict.is_bailout()) {
+                // if (!m_conflict.contains_pvar(v) && !m_conflict.is_bailout()) {
+                if (!m_conflict.is_relevant_pvar(v)) {
                     m_search.pop_assignment();
                     continue;
                 }
                 LOG_H2("Working on " << search_item_pp(m_search, item));
                 LOG(m_justification[v]);
                 LOG("Conflict: " << m_conflict);
-                // inc_activity(v);  // done in resolve_value
                 justification& j = m_justification[v];
                 if (j.level() > base_level() && !m_conflict.resolve_value(v) && j.is_decision()) {
-                    m_conflict.end_conflict();
                     revert_decision(v);
                     return;
                 }
-                if (m_conflict.is_bailout_lemma()) {
+                if (m_conflict.is_backjumping()) {
-                    m_conflict.end_conflict();
+                    backjump_lemma();
-                    backtrack_lemma();
                     return;
                 }
                 m_search.pop_assignment();
@@ -664,36 +649,37 @@ namespace polysat {
                 SASSERT(item.is_boolean());
                 sat::literal const lit = item.lit();
                 sat::bool_var const var = lit.var();
-                if (!m_conflict.is_marked(var))
+                if (!m_conflict.is_relevant(lit))
                     continue;
-
                 LOG_H2("Working on " << search_item_pp(m_search, item));
                 LOG(bool_justification_pp(m_bvars, lit));
                 LOG("Literal " << lit << " is " << lit2cnstr(lit));
                 LOG("Conflict: " << m_conflict);
-                if (m_bvars.is_assumption(var))  // TODO: wouldn't this mean we're already at the base level?
+                if (m_bvars.is_assumption(var)) {
-                    continue;
+                    SASSERT(m_bvars.level(var) <= base_level());
+                    break;
+                }
                 else if (m_bvars.is_bool_propagation(var))
-                    m_conflict.resolve(lit, *m_bvars.reason(lit));
+                    m_conflict.resolve_bool(lit, *m_bvars.reason(lit));
                 else {
                     SASSERT(m_bvars.is_value_propagation(var));
-                    m_conflict.resolve_with_assignment(lit, m_bvars.level(lit));
+                    m_conflict.resolve_with_assignment(lit);
                 }
             }
         }
         LOG("End of resolve_conflict loop");
-        m_conflict.end_conflict();
+        m_conflict.logger().end_conflict();
         report_unsat();
     }
 
     /**
-     * Simple backtracking for lemmas:
+     * Simple backjumping for lemmas:
      * jump to the level where the lemma can be (bool-)propagated,
      * even without reverting the last decision.
      */
-    void solver::backtrack_lemma() {
+    void solver::backjump_lemma() {
-        clause_ref lemma = m_conflict.build_lemma().build();
+        clause_ref lemma = m_conflict.build_lemma();
-        LOG_H2("backtrack_lemma: " << show_deref(lemma));
+        LOG_H2("backjump_lemma: " << show_deref(lemma));
         SASSERT(lemma);
         LOG("Lemma: " << *lemma);
         for (sat::literal lit : *lemma) {
@@ -715,6 +701,7 @@ namespace polysat {
                 jump_level = lit_level;
             }
         }
+        SASSERT(max_level == m_level);  // not required; see comment on max_level
 
         jump_level = std::max(jump_level, base_level());
 
@@ -728,69 +715,6 @@ namespace polysat {
         learn_lemma(*lemma);
     }
 
-    /**
-     * Simpler backtracking for forbidden interval lemmas:
-     * since forbidden intervals already gives us a lemma where the conflict variable has been eliminated,
-     * we can backtrack to the last relevant decision and learn this lemma.
-     */
-    void solver::backtrack_fi() {
-        uint_set relevant_vars;
-        search_iterator search_it(m_search);
-        while (search_it.next()) {
-            auto& item = *search_it;
-            search_it.set_resolved();
-            if (item.is_assignment()) {
-                // Resolve over variable assignment
-                pvar v = item.var();
-                if (!m_conflict.pvar_occurs_in_constraints(v) && !relevant_vars.contains(v)) {
-                    m_search.pop_assignment();
-                    continue;
-                }
-                LOG_H2("Working on " << search_item_pp(m_search, item));
-                LOG(m_justification[v]);
-                LOG("Conflict: " << m_conflict);
-                inc_activity(v);
-                justification& j = m_justification[v];
-                if (j.level() > base_level() && j.is_decision()) {
-                    m_conflict.end_conflict();
-                    revert_decision(v);
-                    return;
-                }
-                SASSERT(j.is_propagation());
-                // If a variable was propagated:
-                // we don't really care about the constraints in this case, but just about the variables it depends on
-                for (auto const& c : m_viable.get_constraints(v))
-                    for (pvar v : c->vars()) {
-                        relevant_vars.insert(v);
-                        m_conflict.log_var(v);
-                    }
-                m_search.pop_assignment();
-            }
-            else {
-                // Resolve over boolean literal
-                SASSERT(item.is_boolean());
-                sat::literal const lit = item.lit();
-                sat::bool_var const var = lit.var();
-                if (!m_conflict.is_marked(var))
-                    continue;
-                LOG_H2("Working on " << search_item_pp(m_search, item));
-                LOG(bool_justification_pp(m_bvars, lit));
-                LOG("Literal " << lit << " is " << lit2cnstr(lit));
-                LOG("Conflict: " << m_conflict);
-                if (m_bvars.is_assumption(var))  // TODO: wouldn't this mean we're already at the base level?
-                    continue;
-                else if (m_bvars.is_bool_propagation(var))
-                    m_conflict.resolve(lit, *m_bvars.reason(lit));
-                else {
-                    SASSERT(m_bvars.is_value_propagation(var));
-                    continue;
-                }
-            }
-        }
-        m_conflict.end_conflict();
-        report_unsat();
-    }
-
     /**
     * Variable activity accounting.
     * As a placeholder we increment activity 
@@ -839,6 +763,7 @@ namespace polysat {
         LOG("Learning: "<< lemma);
         SASSERT(!lemma.empty());
         m_simplify_clause.apply(lemma);
+        // TODO: print warning if the lemma is non-asserting?
         add_clause(lemma);
     }
 
@@ -858,7 +783,7 @@ namespace polysat {
         LOG_H3("Reverting decision: pvar " << v << " := " << val);
         SASSERT(m_justification[v].is_decision());
 
-        clause_ref lemma = m_conflict.build_lemma().build();
+        clause_ref lemma = m_conflict.build_lemma();
         if (lemma->empty())
             report_unsat();
         else {
@@ -887,7 +812,7 @@ namespace polysat {
     }
 
     void solver::assign_eval(sat::literal lit) {
-        SASSERT(lit2cnstr(lit).is_currently_true(*this));
+        // SASSERT(lit2cnstr(lit).is_currently_true(*this));  // "morally" this should hold, but currently fails because of pop_assignment during resolve_conflict
         unsigned level = 0;
         // NOTE: constraint may be evaluated even if some variables are still unassigned (e.g., 0*x doesn't depend on x).
         for (auto v : lit2cnstr(lit)->vars())
@@ -934,12 +859,13 @@ namespace polysat {
     void solver::add_clause(clause& clause) {
         LOG((clause.is_redundant() ? "Lemma: ": "Aux: ") << clause);
         for (sat::literal lit : clause) {
-            LOG("   Literal " << lit << " is: " << lit_pp(*this, lit));
+            LOG("   " << lit_pp(*this, lit));
             // SASSERT(m_bvars.value(lit) != l_true);
             // it could be that such a literal has been created previously but we don't detect it when e.g. narrowing a mul_ovfl_constraint
             if (m_bvars.value(lit) == l_true) {
                 // in this case the clause is useless
                 LOG("   Clause is already true, skipping...");
+                // SASSERT(false);  // should never happen (at least for redundant clauses)
                 return;
             }
         }
@@ -1106,12 +1032,14 @@ namespace polysat {
      * Check that two variables of each constraint are watched.
      */
     bool solver::wlist_invariant() {
+#if 0
         for (pvar v = 0; v < m_value.size(); ++v) {
             std::stringstream s;
             for (constraint* c : m_pwatch[v])
                 s << " " << c->bvar();
             LOG("Watch for v" << v << ": " << s.str());
         }
+#endif
         // Skip boolean variables that aren't active yet
         uint_set skip;
         for (unsigned i = m_qhead; i < m_search.size(); ++i)

src/math/polysat/solver.h

@@ -22,7 +22,6 @@ Author:
 #include "util/params.h"
 #include "math/polysat/boolean.h"
 #include "math/polysat/conflict.h"
-#include "math/polysat/conflict2.h"
 #include "math/polysat/constraint.h"
 #include "math/polysat/clause_builder.h"
 #include "math/polysat/simplify_clause.h"
@@ -37,8 +36,6 @@ Author:
 #include "math/polysat/viable.h"
 #include "math/polysat/log.h"
 
-
-
 namespace polysat {
 
     struct config {
@@ -70,14 +67,12 @@ namespace polysat {
         friend class clause;
         friend class clause_builder;
         friend class conflict;
-        friend class conflict2;
         friend class conflict_explainer;
         friend class simplify_clause;
         friend class simplify;
         friend class restart;
         friend class explainer;
         friend class inference_engine;
-        friend class old_inference_logger;
         friend class file_inference_logger;
         friend class forbidden_intervals;
         friend class linear_solver;
@@ -94,7 +89,6 @@ namespace polysat {
         friend class scoped_solverv;        
         friend class test_polysat;
         friend class test_fi;
-        friend struct inference_resolve_with_assignment;
         friend struct inf_resolve_with_assignment;
 
         reslimit&                m_lim;
@@ -105,7 +99,6 @@ namespace polysat {
         viable_fallback          m_viable_fallback;   // fallback for viable, using bitblasting over univariate constraints
         linear_solver            m_linear_solver;
         conflict                 m_conflict;
-        conflict2                m_conflict2;
         simplify_clause          m_simplify_clause;
         simplify                 m_simplify;
         restart                  m_restart;
@@ -192,9 +185,9 @@ namespace polysat {
         void erase_pwatch(pvar v, constraint* c);
         void erase_pwatch(constraint* c);
 
-        void set_conflict(signed_constraint c) { m_conflict.set(c); }
+        void set_conflict(signed_constraint c) { m_conflict.init(c); }
-        void set_conflict(clause& cl) { m_conflict.set(cl); }
+        void set_conflict(clause& cl) { m_conflict.init(cl); }
-        void set_conflict(pvar v) { m_conflict.set(v); }
+        void set_conflict(pvar v, bool by_viable_fallback) { m_conflict.init(v, by_viable_fallback); }
 
         bool can_decide() const { return !m_free_pvars.empty(); }
         void decide();
@@ -202,14 +195,12 @@ namespace polysat {
 
         void linear_propagate();
 
-
         bool is_conflict() const { return !m_conflict.empty(); }
         bool at_base_level() const;
         unsigned base_level() const;
 
         void resolve_conflict();
-        void backtrack_fi();
+        void backjump_lemma();
-        void backtrack_lemma();
         void revert_decision(pvar v);
         void revert_bool_decision(sat::literal lit);
 
@@ -461,7 +452,4 @@ namespace polysat {
 
     inline std::ostream& operator<<(std::ostream& out, assignments_pp const& a) { return a.display(out); }
 
-
 }
-
-

src/math/polysat/viable.cpp

@@ -29,9 +29,19 @@ TODO: improve management of the fallback univariate solvers:
 #include "util/debug.h"
 #include "math/polysat/viable.h"
 #include "math/polysat/solver.h"
+#include "math/polysat/univariate/univariate_solver.h"
 
 namespace polysat {
 
+    struct inf_fi : public inference {
+        viable& v;
+        pvar var;
+        inf_fi(viable& v, pvar var) : v(v), var(var) {}
+        std::ostream& display(std::ostream& out) const override {
+            return out << "Forbidden intervals for v" << var << ": " << viable::var_pp(v, var);
+        }
+    };
+
     viable::viable(solver& s):
         s(s),
         m_forbidden_intervals(s) {
@@ -124,7 +134,7 @@ namespace polysat {
                 prop = true;
                 break;
             case dd::find_t::empty:
-                s.set_conflict(v);
+                s.set_conflict(v, false);
                 return true;
             default:
                 break;
@@ -185,7 +195,6 @@ namespace polysat {
             return false;
         }
 
-
         auto create_entry = [&]() {
             m_trail.push_back({ v, entry_kind::unit_e, ne });
             s.m_trail.push_back(trail_instr_t::viable_add_i);
@@ -620,20 +629,6 @@ namespace polysat {
             return dd::find_t::multiple;
     }
 
-    struct inference_fi : public inference {
-        viable& v;
-        pvar var;
-        inference_fi(viable& v, pvar var) : v(v), var(var) {}
-        std::ostream& display(std::ostream& out) const override {
-            return out << "Forbidden intervals for v" << var << ": " << viable::var_pp(v, var);
-        }
-    };
-
-    bool viable::resolve(pvar v, conflict2& core) {
-        NOT_IMPLEMENTED_YET();
-        return false;
-    }
-
     bool viable::resolve(pvar v, conflict& core) {
         if (has_viable(v))
             return false;
@@ -652,7 +647,7 @@ namespace polysat {
                 auto lhs = hi - next_lo;
                 auto rhs = next_hi - next_lo;
                 signed_constraint c = s.m_constraints.ult(lhs, rhs);
-                core.propagate(c);
+                core.insert_eval(c);
 #if 0
                 if (n != first) {
                     while {
@@ -667,20 +662,25 @@ namespace polysat {
 #endif
             }
             for (auto sc : e->side_cond)
-                core.propagate(sc);
+                core.insert_eval(sc);
             core.insert(e->src);
             e = n;
         }
         while (e != first);
+        core.logger().log(inf_fi(*this, v));
 
+        // TODO: should not be here, too general
+        /*
         for (auto c : core) {
             if (c.bvalue(s) == l_false) {
                 core.reset();
                 core.set(~c);
+                core.logger().log("");
                 break;
             }
         }
-        core.log_inference(inference_fi(*this, v));
+        */
+
         return true;
     }
 

src/math/polysat/viable.h

@@ -23,14 +23,14 @@ Author:
 #include "util/small_object_allocator.h"
 #include "math/polysat/types.h"
 #include "math/polysat/conflict.h"
-#include "math/polysat/conflict2.h"
 #include "math/polysat/constraint.h"
 #include "math/polysat/forbidden_intervals.h"
-#include "math/polysat/univariate/univariate_solver.h"
 
 namespace polysat {
 
     class solver;
+    class univariate_solver;
+    class univariate_solver_factory;
 
     class viable {
         friend class test_fi;
@@ -112,7 +112,6 @@ namespace polysat {
         * \pre there are no viable values for v
         */
         bool resolve(pvar v, conflict& core);
-        bool resolve(pvar v, conflict2& core);
 
         /** Log all viable values for the given variable.
          * (Inefficient, but useful for debugging small instances.)