add hint verification, combine bounds/farkas into one rule

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

src/sat/dimacs.cpp

@@ -115,7 +115,6 @@ static void read_clause(Buffer & in, std::ostream& err, sat::literal_vector & li
 template<typename Buffer>
 static void read_pragma(Buffer & in, std::ostream& err, std::string& p, sat::proof_hint& h) {
     skip_whitespace(in);
-    h.reset();
     if (*in != 'p')
         return;
     ++in;
@@ -307,6 +306,7 @@ namespace dimacs {
         loop:
             skip_whitespace(in);
             m_record.m_pragma.clear();
+            m_record.m_hint.reset();
             switch (*in) {
             case EOF:
                 return false;                

src/sat/sat_drat.cpp

@@ -918,9 +918,6 @@ namespace sat {
         case hint_type::farkas_h:
             ous << "farkas ";
             break;
-        case hint_type::bound_h:
-            ous << "bound ";
-            break;
         case hint_type::cut_h:
             ous << "cut ";
             break;
@@ -949,11 +946,6 @@ namespace sat {
                 s += 6;
                 return true;
             }
-            if (0 == strncmp(s, "bound", 5)) {
-                h.m_ty = hint_type::bound_h;
-                s += 5;
-                return true;
-            }
             return false;
         };
 

src/sat/sat_types.h

@@ -97,7 +97,6 @@ namespace sat {
     enum class hint_type {
         null_h,
         farkas_h,
-        bound_h,
         cut_h
     };
 

src/sat/smt/arith_diagnostics.cpp

@@ -81,13 +81,14 @@ namespace arith {
     }
 
     /**
-     * Assumption:
+     * It may be necessary to use the following assumption when checking Farkas claims
+     * generated from bounds propagation:
      * A bound literal ax <= b is explained by a set of weighted literals
      * r1*(a1*x <= b1) + .... + r_k*(a_k*x <= b_k), where r_i > 0
      * such that there is a r >= 1
      * (r1*a1+..+r_k*a_k) = r*a, (r1*b1+..+r_k*b_k) <= r*b
      */
-    sat::proof_hint const* solver::explain(sat::hint_type ty) {
+    sat::proof_hint const* solver::explain(sat::hint_type ty, sat::literal lit) {
         if (!ctx.use_drat())
             return nullptr;
         m_bounds_pragma.m_ty = ty;
@@ -105,6 +106,8 @@ namespace arith {
             }
             case equality_source: {
                 auto [u, v] = m_equalities[idx];
+                ctx.drat_log_expr(u->get_expr());
+                ctx.drat_log_expr(v->get_expr());
                 m_bounds_pragma.m_eqs.push_back({ev.coeff(), u->get_expr_id(), v->get_expr_id()});
                 break;
             }
@@ -112,6 +115,8 @@ namespace arith {
                 break;
             }
         }
+        if (lit != sat::null_literal)
+            m_bounds_pragma.m_literals.push_back({rational(1), ~lit});
         return &m_bounds_pragma;
     }
 }

src/sat/smt/arith_solver.cpp

@@ -263,7 +263,7 @@ namespace arith {
             TRACE("arith", for (auto lit : m_core) tout << lit << ": " << s().value(lit) << "\n";);
             DEBUG_CODE(for (auto lit : m_core) { VERIFY(s().value(lit) == l_true); });
             ++m_stats.m_bound_propagations1;
-            assign(lit, m_core, m_eqs, explain(sat::hint_type::bound_h));
+            assign(lit, m_core, m_eqs, explain(sat::hint_type::farkas_h, lit));
         }
 
         if (should_refine_bounds() && first)
@@ -378,7 +378,7 @@ namespace arith {
         reset_evidence();
         m_explanation.clear();
         lp().explain_implied_bound(be, m_bp);
-        assign(bound, m_core, m_eqs, explain(sat::hint_type::bound_h));
+        assign(bound, m_core, m_eqs, explain(sat::hint_type::farkas_h, bound));
     }
 
 
@@ -1177,7 +1177,7 @@ namespace arith {
             app_ref b = mk_bound(m_lia->get_term(), m_lia->get_offset(), !m_lia->is_upper());
             IF_VERBOSE(4, verbose_stream() << "cut " << b << "\n");
             literal lit = expr2literal(b);
-            assign(lit, m_core, m_eqs, explain(sat::hint_type::cut_h));
+            assign(lit, m_core, m_eqs, explain(sat::hint_type::cut_h, lit));
             lia_check = l_false;
             break;
         }

src/sat/smt/arith_solver.h

@@ -421,7 +421,7 @@ namespace arith {
 
         sat::proof_hint m_bounds_pragma;
         sat::proof_hint m_farkas2;
-        sat::proof_hint const* explain(sat::hint_type ty);
+        sat::proof_hint const* explain(sat::hint_type ty, sat::literal lit = sat::null_literal);
 
 
     public:

src/sat/smt/euf_solver.h

@@ -176,7 +176,6 @@ namespace euf {
         void log_antecedents(literal l, literal_vector const& r);
         void log_justification(literal l, th_explain const& jst);
         void drat_log_decl(func_decl* f);
-        void drat_log_expr(expr* n);
         void drat_log_expr1(expr* n);
         ptr_vector<expr> m_drat_todo;
         obj_hashtable<ast> m_drat_asts;
@@ -345,6 +344,7 @@ namespace euf {
         sat::drat& get_drat() { return s().get_drat(); }
         void drat_bool_def(sat::bool_var v, expr* n);
         void drat_eq_def(sat::literal lit, expr* eq);
+        void drat_log_expr(expr* n);
 
         // decompile
         bool extract_pb(std::function<void(unsigned sz, literal const* c, unsigned k)>& card,