fix proof generation for euf-solver

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

src/sat/smt/arith_diagnostics.cpp

@@ -213,7 +213,9 @@ namespace arith {
             args.push_back(s.literal2expr(lit));
         }
         for (unsigned i = m_eq_head; i < m_eq_tail; ++i) {
-            auto const& [x, y, is_eq] = a.m_arith_hint.eq(i);            
+            auto [x, y, is_eq] = a.m_arith_hint.eq(i);    
+            if (x->get_id() > y->get_id())
+                std::swap(x, y);
             expr_ref eq(m.mk_eq(x->get_expr(), y->get_expr()), m);
             if (!is_eq) eq = m.mk_not(eq);
             args.push_back(arith.mk_int(1));

src/sat/smt/euf_proof.cpp

@@ -44,17 +44,73 @@ namespace euf {
     }
 
     /**
-     * \brief logs antecedents to a proof trail.
-     *
-     * NB with theories, this is not a pure EUF justification,
-     * It is true modulo EUF and previously logged certificates
-     * so it isn't necessarily an axiom over EUF,
-     * We will here leave it to the EUF checker to perform resolution steps.
-     */
+    * Log justifications.
+    * is_euf - true if l is justified by congruence closure. In this case create a congruence closure proof.
+    * explain_size - the relevant portion of premises for the congruence closure proof.
+    * The EUF solver manages equality propagation. Each propagated equality is justified by a congruence closure.
+    */
+    void solver::log_justifications(literal l, unsigned explain_size, bool is_euf) {
+
+        unsigned nv = s().num_vars();
+        expr_ref_vector eqs(m);
+
+        auto add_hint_literals = [&](unsigned sz) {
+            eqs.reset();
+            m_hint_lits.reset();
+            nv = s().num_vars();
+            for (unsigned i = 0; i < sz; ++i) {
+                size_t* e = m_explain[i];
+                if (is_literal(e))
+                    m_hint_lits.push_back(get_literal(e));
+                else {
+                    auto [x, y] = th_explain::from_index(get_justification(e)).eq_consequent();
+                    eqs.push_back(m.mk_eq(x->get_expr(), y->get_expr()));
+                    set_tmp_bool_var(nv, eqs.back());
+                    m_hint_lits.push_back(literal(nv, false));
+                    ++nv;
+                }
+            }
+        };
+
+        auto clear_hint_literals = [&]() {
+            for (unsigned v = s().num_vars(); v < nv; ++v)
+                set_tmp_bool_var(v, nullptr);
+        };
+
+        // log EUF justifications
+        if (is_euf) {
+            add_hint_literals(explain_size);
+            auto* hint = mk_hint(m_euf, l);
+            log_antecedents(l, m_hint_lits, hint);
+            clear_hint_literals();
+        }
+
+        // explain equalities
+        for (auto const& [a, b] : m_hint_eqs) {
+            m_egraph.begin_explain();
+            m_explain.reset();
+            m_egraph.explain_eq<size_t>(m_explain, &m_explain_cc, a, b);
+            m_egraph.end_explain();
+            // Detect shortcut if equality is explained directly by a theory
+            if (m_explain.size() == 1 && !is_literal(m_explain[0])) {
+                auto const& [x, y] = th_explain::from_index(get_justification(m_explain[0])).eq_consequent();
+                if (x == a && y == b)
+                    continue;
+            }
+            add_hint_literals(m_explain.size());
+            eqs.push_back(m.mk_eq(a->get_expr(), b->get_expr()));
+            set_tmp_bool_var(nv, eqs.back());
+            sat::literal eql = literal(nv, false);
+            ++nv;
+            auto* hint = mk_hint(m_euf, eql);
+            log_antecedents(eql, m_hint_lits, hint);
+            clear_hint_literals();
+        }
+    }
+
     void solver::log_antecedents(literal l, literal_vector const& r, th_proof_hint* hint) {
+        SASSERT(hint && use_drat());
         TRACE("euf", log_antecedents(tout, l, r); tout << mk_pp(hint->get_hint(*this), m) << "\n");
-        if (!use_drat())
-            return;
         literal_vector lits;
         for (literal lit : r) 
             lits.push_back(~lit);
@@ -63,6 +119,15 @@ namespace euf {
         get_drat().add(lits, sat::status::th(true, get_id(), hint));
     }
 
+    void solver::log_rup(literal l, literal_vector const& r) {
+        literal_vector lits;
+        for (literal lit : r)
+            lits.push_back(~lit);
+        if (l != sat::null_literal)
+            lits.push_back(l);
+        get_drat().add(lits, sat::status::redundant());
+    }
+
     void solver::log_antecedents(std::ostream& out, literal l, literal_vector const& r) {
         for (sat::literal l : r) {
             expr* n = m_bool_var2expr[l.var()];
@@ -159,6 +224,7 @@ namespace euf {
         };
         for (unsigned i = m_lit_head; i < m_lit_tail; ++i) 
             args.push_back(s.literal2expr(s.m_proof_literals[i]));
+        
         std::sort(s.m_explain_cc.data() + m_cc_head, s.m_explain_cc.data() + m_cc_tail, compare_ts);
         for (unsigned i = m_cc_head; i < m_cc_tail; ++i) {
             auto const& [a, b, ts, comm] = s.m_explain_cc[i];

src/sat/smt/euf_solver.cpp

@@ -228,69 +228,52 @@ namespace euf {
 
     void solver::get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing) {
         bool create_hint = use_drat() && !probing;
-        m_egraph.begin_explain();
-        m_explain.reset();
         if (create_hint) {
             push(restore_vector(m_explain_cc));
             m_hint_eqs.reset();
-            m_hint_lits.reset();
         }
         auto* ext = sat::constraint_base::to_extension(idx);
-        th_proof_hint* hint = nullptr;
+        bool is_euf = ext == this;
+        bool multiple_theories = false;
 
-        if (ext == this)
+        m_egraph.begin_explain();
+        m_explain.reset();
+        if (is_euf)
             get_euf_antecedents(l, constraint::from_idx(idx), r, probing);
         else 
             ext->get_antecedents(l, idx, r, probing);
 
-        if (create_hint && ext != this)
-            ext->get_antecedents(l, idx, m_hint_lits, probing);
+        unsigned ez = m_explain.size();
 
         for (unsigned qhead = 0; qhead < m_explain.size(); ++qhead) {
             size_t* e = m_explain[qhead];
             if (is_literal(e)) 
                 r.push_back(get_literal(e));            
             else {
+                multiple_theories = true;
                 size_t idx = get_justification(e);
                 auto* ext = sat::constraint_base::to_extension(idx);
                 SASSERT(ext != this);
                 sat::literal lit = sat::null_literal;
                 ext->get_antecedents(lit, idx, r, probing);
             }
-            if (create_hint) {
-                if (is_literal(e))
-                    m_hint_lits.push_back(get_literal(e));
-                else {
-                    auto const& eq = th_explain::from_index(get_justification(e)).eq_consequent();
-                    TRACE("euf", tout << "consequent " << bpp(eq.first) << " " << bpp(eq.second) << "\n"; );
-                    m_hint_eqs.push_back(eq);
-                }
-            }
         }
         m_egraph.end_explain();
 
         CTRACE("euf", probing, tout << "explain " << l << " <- " << r << "\n");
         unsigned j = 0;
-        for (sat::literal lit : r) 
-            if (s().lvl(lit) > 0) r[j++] = lit;
+        for (auto lit : r)
+            if (s().lvl(lit) > 0)
+                r[j++] = lit;
+        bool reduced = j < r.size();
         r.shrink(j);
-        CTRACE("euf", create_hint, tout << "explain " << l << " <- " << m_hint_lits << "\n");
+                        
         DEBUG_CODE(for (auto lit : r) SASSERT(s().value(lit) == l_true););
 
-        if (create_hint)  {
-            unsigned nv = s().num_vars();
-            expr_ref_vector eqs(m);
-            // add equalities to hint.            
-            for (auto const& [a,b] : m_hint_eqs) {
-                eqs.push_back(m.mk_eq(a->get_expr(), b->get_expr()));
-                set_tmp_bool_var(nv, eqs.back());
-                m_hint_lits.push_back(literal(nv, false));
-                ++nv;
-            }
-            hint = mk_hint(m_euf, l);
-            log_antecedents(l, r, hint);
-            for (unsigned v = s().num_vars(); v < nv; ++v)
-                set_tmp_bool_var(v, nullptr);
+        if (create_hint) {
+            log_justifications(l, ez, is_euf);
+            if (reduced || multiple_theories)
+                log_rup(l, r);
         }
     }
 
@@ -305,11 +288,12 @@ namespace euf {
     }
 
     void solver::add_eq_antecedent(bool probing, enode* a, enode* b) {
-        cc_justification* cc = (!probing && use_drat()) ? &m_explain_cc : nullptr;
-        m_egraph.explain_eq<size_t>(m_explain, cc, a, b);
+        if (!probing && use_drat())
+            m_hint_eqs.push_back({a, b});
+        m_egraph.explain_eq<size_t>(m_explain, nullptr, a, b);
     }
 
-    void solver::add_diseq_antecedent(ptr_vector<size_t>& ex, cc_justification* cc, enode* a, enode* b) {
+    void solver::explain_diseq(ptr_vector<size_t>& ex, cc_justification* cc, enode* a, enode* b) {
         sat::bool_var v = get_egraph().explain_diseq(ex, cc, a, b);
         SASSERT(v == sat::null_bool_var || s().value(v) == l_false);
         if (v != sat::null_bool_var) 

src/sat/smt/euf_solver.h

@@ -228,6 +228,8 @@ namespace euf {
         void log_antecedents(std::ostream& out, literal l, literal_vector const& r);
         void log_antecedents(literal l, literal_vector const& r, th_proof_hint* hint);
         void log_justification(literal l, th_explain const& jst);
+        void log_justifications(literal l, unsigned explain_size, bool is_euf);
+        void log_rup(literal l, literal_vector const& r);
 
 
         eq_proof_hint* mk_hint(symbol const& th, literal lit);
@@ -367,7 +369,7 @@ namespace euf {
         void get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing) override;
         void get_th_antecedents(literal l, th_explain& jst, literal_vector& r, bool probing);
         void add_eq_antecedent(bool probing, enode* a, enode* b);
-        void add_diseq_antecedent(ptr_vector<size_t>& ex, cc_justification* cc, enode* a, enode* b);
+        void explain_diseq(ptr_vector<size_t>& ex, cc_justification* cc, enode* a, enode* b);
         void add_explain(size_t* p) { m_explain.push_back(p); }
         void reset_explain() { m_explain.reset(); }
         void set_eliminated(bool_var v) override;

src/sat/smt/q_ematch.cpp

@@ -125,7 +125,7 @@ namespace q {
             if (a->get_root() == b->get_root())
                 ctx.get_egraph().explain_eq<size_t>(m_explain, cc, a, b);
             else
-                ctx.add_diseq_antecedent(m_explain, cc, a, b);
+                ctx.explain_diseq(m_explain, cc, a, b);
         }
         ctx.get_egraph().end_explain();
 

src/sat/smt/sat_th.cpp

@@ -228,6 +228,8 @@ namespace euf {
     th_explain::th_explain(unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs, sat::literal c, enode_pair const& p, th_proof_hint const* pma) {
         m_consequent = c;
         m_eq = p;
+        if (m_eq.first && m_eq.first->get_id() > m_eq.second->get_id())
+            std::swap(m_eq.first, m_eq.second);
         m_proof_hint = pma;
         m_num_literals = n_lits;
         m_num_eqs = n_eqs;
@@ -238,8 +240,11 @@ namespace euf {
             m_literals[i] = lits[i];
         base_ptr += sizeof(literal) * n_lits;
         m_eqs = reinterpret_cast<enode_pair*>(base_ptr);
-        for (i = 0; i < n_eqs; ++i)
+        for (i = 0; i < n_eqs; ++i) {
             m_eqs[i] = eqs[i];
+            if (m_eqs[i].first->get_id() > m_eqs[i].second->get_id())
+                std::swap(m_eqs[i].first, m_eqs[i].second);
+        }
     }
 
     th_explain* th_explain::mk(th_euf_solver& th, unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs, sat::literal c, enode* x, enode* y, th_proof_hint const* pma) {