rename propagation to explain

src/sat/smt/arith_diagnostics.cpp

@@ -69,7 +69,7 @@ namespace arith {
     }
 
     std::ostream& solver::display_justification(std::ostream& out, sat::ext_justification_idx idx) const { 
-        return euf::th_propagation::from_index(idx).display(out);
+        return euf::th_explain::from_index(idx).display(out);
     }
 
     std::ostream& solver::display_constraint(std::ostream& out, sat::ext_constraint_idx idx) const { 

src/sat/smt/arith_solver.cpp

@@ -318,7 +318,7 @@ namespace arith {
         reset_evidence();
         for (auto const& ev : e)
             set_evidence(ev.ci(), m_core, m_eqs);
-        auto* jst = euf::th_propagation::propagate(*this, m_core, m_eqs, n1, n2);
+        auto* jst = euf::th_explain::propagate(*this, m_core, m_eqs, n1, n2);
         ctx.propagate(n1, n2, jst->to_index());
     }
 
@@ -718,7 +718,7 @@ namespace arith {
         set_evidence(ci4, m_core, m_eqs);
         enode* x = var2enode(v1);
         enode* y = var2enode(v2);
-        auto* jst = euf::th_propagation::propagate(*this, m_core, m_eqs, x, y);
+        auto* jst = euf::th_explain::propagate(*this, m_core, m_eqs, x, y);
         ctx.propagate(x, y, jst->to_index());
     }
 
@@ -1141,7 +1141,7 @@ namespace arith {
             add_clause(m_core2);
         }
         else {
-            auto* jst = euf::th_propagation::propagate(*this, core, eqs, lit);
+            auto* jst = euf::th_explain::propagate(*this, core, eqs, lit);
             ctx.propagate(lit, jst->to_index());
         }
     }
@@ -1419,7 +1419,7 @@ namespace arith {
     }
 
     void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) {
-        auto& jst = euf::th_propagation::from_index(idx);
+        auto& jst = euf::th_explain::from_index(idx);
         ctx.get_antecedents(l, jst, r, probing);
     }
 

src/sat/smt/dt_solver.cpp

@@ -105,7 +105,7 @@ namespace dt {
             add_unit(eq_internalize(e1, e2));
         else if (s().value(antecedent) == l_true) {
             euf::enode* n2 = e_internalize(e2);
-            ctx.propagate(n1, n2, euf::th_propagation::propagate(*this, antecedent, n1, n2));
+            ctx.propagate(n1, n2, euf::th_explain::propagate(*this, antecedent, n1, n2));
         }
         else
             add_clause(~antecedent, eq_internalize(e1, e2));
@@ -160,7 +160,7 @@ namespace dt {
         literal l = ctx.enode2literal(r);
         SASSERT(s().value(l) == l_false);
         clear_mark();
-        ctx.set_conflict(euf::th_propagation::conflict(*this, ~l, c, r->get_arg(0)));
+        ctx.set_conflict(euf::th_explain::conflict(*this, ~l, c, r->get_arg(0)));
     }
 
     /**
@@ -315,7 +315,7 @@ namespace dt {
                 break;
             }
         }
-        ctx.set_conflict(euf::th_propagation::conflict(*this, m_lits));
+        ctx.set_conflict(euf::th_explain::conflict(*this, m_lits));
     }
 
 
@@ -462,7 +462,7 @@ namespace dt {
         }
         TRACE("dt", tout << "propagate " << num_unassigned << " eqs: " << eqs.size() << "\n";);
         if (num_unassigned == 0)
-            ctx.set_conflict(euf::th_propagation::conflict(*this, m_lits, eqs));
+            ctx.set_conflict(euf::th_explain::conflict(*this, m_lits, eqs));
         else if (num_unassigned == 1) {
             // propagate remaining recognizer
             SASSERT(!m_lits.empty());
@@ -476,7 +476,7 @@ namespace dt {
                 app_ref rec_app(m.mk_app(rec, n->get_expr()), m);
                 consequent = mk_literal(rec_app);
             }
-            ctx.propagate(consequent, euf::th_propagation::propagate(*this, m_lits, eqs, consequent));
+            ctx.propagate(consequent, euf::th_explain::propagate(*this, m_lits, eqs, consequent));
         }
         else if (get_config().m_dt_lazy_splits == 0 || (!srt->is_infinite() && get_config().m_dt_lazy_splits == 1))
             // there are more than 2 unassigned recognizers...
@@ -493,7 +493,7 @@ namespace dt {
         auto* con1 = d1->m_constructor;
         auto* con2 = d2->m_constructor;
         if (con1 && con2 && con1->get_decl() != con2->get_decl())
-            ctx.set_conflict(euf::th_propagation::conflict(*this, con1, con2));
+            ctx.set_conflict(euf::th_explain::conflict(*this, con1, con2));
         else if (con2 && !con1) {
             ctx.push(set_ptr_trail<enode>(d1->m_constructor));
             // check whether there is a recognizer in d1 that conflicts with con2;
@@ -663,7 +663,7 @@ namespace dt {
 
         if (res) {
             clear_mark();
-            ctx.set_conflict(euf::th_propagation::conflict(*this, m_used_eqs));
+            ctx.set_conflict(euf::th_explain::conflict(*this, m_used_eqs));
             TRACE("dt", tout << "occurs check conflict: " << ctx.bpp(n) << "\n";);
         }
         return res;
@@ -704,7 +704,7 @@ namespace dt {
     }
 
     void solver::get_antecedents(literal l, sat::ext_justification_idx idx, literal_vector& r, bool probing) {
-        auto& jst = euf::th_propagation::from_index(idx);
+        auto& jst = euf::th_explain::from_index(idx);
         ctx.get_antecedents(l, jst, r, probing);
     }
 

src/sat/smt/dt_solver.h

@@ -140,7 +140,7 @@ namespace dt {
         sat::check_result check() override;
 
         std::ostream& display(std::ostream& out) const override;
-        std::ostream& display_justification(std::ostream& out, sat::ext_justification_idx idx) const override { return euf::th_propagation::from_index(idx).display(out); }
+        std::ostream& display_justification(std::ostream& out, sat::ext_justification_idx idx) const override { return euf::th_explain::from_index(idx).display(out); }
         std::ostream& display_constraint(std::ostream& out, sat::ext_constraint_idx idx) const override { return display_justification(out, idx); }
         void collect_statistics(statistics& st) const override;
         euf::th_solver* clone(euf::solver& ctx) override;

src/sat/smt/euf_proof.cpp

@@ -126,7 +126,7 @@ namespace euf {
         }
     }
 
-    void solver::log_justification(literal l, th_propagation const& jst) {
+    void solver::log_justification(literal l, th_explain const& jst) {
         literal_vector lits;
         unsigned nv = s().num_vars();
         expr_ref_vector eqs(m);
@@ -138,11 +138,11 @@ namespace euf {
             return lit;
         };
 
-        for (auto lit : euf::th_propagation::lits(jst))
+        for (auto lit : euf::th_explain::lits(jst))
             lits.push_back(~lit);
         if (l != sat::null_literal)
             lits.push_back(l);
-        for (auto eq : euf::th_propagation::eqs(jst)) 
+        for (auto eq : euf::th_explain::eqs(jst)) 
             lits.push_back(~add_lit(eq));
         if (jst.lit_consequent() != sat::null_literal && jst.lit_consequent() != l) 
             lits.push_back(jst.lit_consequent());

src/sat/smt/euf_solver.cpp

@@ -218,10 +218,10 @@ namespace euf {
             log_antecedents(l, r);
     }
 
-    void solver::get_antecedents(literal l, th_propagation& jst, literal_vector& r, bool probing) {
+    void solver::get_antecedents(literal l, th_explain& jst, literal_vector& r, bool probing) {
-        for (auto lit : euf::th_propagation::lits(jst))
+        for (auto lit : euf::th_explain::lits(jst))
             r.push_back(lit);
-        for (auto eq : euf::th_propagation::eqs(jst))
+        for (auto eq : euf::th_explain::eqs(jst))
             add_antecedent(eq.first, eq.second);
 
         if (!probing && use_drat()) 

src/sat/smt/euf_solver.h

@@ -167,7 +167,7 @@ namespace euf {
         // proofs
         void log_antecedents(std::ostream& out, literal l, literal_vector const& r);
         void log_antecedents(literal l, literal_vector const& r);
-        void log_justification(literal l, th_propagation const& jst);
+        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);
@@ -282,15 +282,15 @@ namespace euf {
         bool propagate(enode* a, enode* b, ext_justification_idx idx);
         void set_conflict(ext_justification_idx idx);
 
-        void propagate(literal lit, th_propagation* p) { propagate(lit, p->to_index()); }
+        void propagate(literal lit, th_explain* p) { propagate(lit, p->to_index()); }
-        bool propagate(enode* a, enode* b, th_propagation* p) { return propagate(a, b, p->to_index()); }
+        bool propagate(enode* a, enode* b, th_explain* p) { return propagate(a, b, p->to_index()); }
-        void set_conflict(th_propagation* p) { set_conflict(p->to_index()); }
+        void set_conflict(th_explain* p) { set_conflict(p->to_index()); }
 
         bool set_root(literal l, literal r) override;
         void flush_roots() override;
 
         void get_antecedents(literal l, ext_justification_idx idx, literal_vector& r, bool probing) override;
-        void get_antecedents(literal l, th_propagation& jst, literal_vector& r, bool probing);
+        void get_antecedents(literal l, th_explain& jst, literal_vector& r, bool probing);
         void add_antecedent(enode* a, enode* b);
         void add_diseq_antecedent(enode* a, enode* b);
         void asserted(literal l) override;

src/sat/smt/sat_th.cpp

@@ -225,73 +225,73 @@ namespace euf {
         return ctx.s().rand()();
     }
 
-    size_t th_propagation::get_obj_size(unsigned num_lits, unsigned num_eqs) {
+    size_t th_explain::get_obj_size(unsigned num_lits, unsigned num_eqs) {
-        return sat::constraint_base::obj_size(sizeof(th_propagation) + sizeof(sat::literal) * num_lits + sizeof(enode_pair) * num_eqs);
+        return sat::constraint_base::obj_size(sizeof(th_explain) + sizeof(sat::literal) * num_lits + sizeof(enode_pair) * num_eqs);
     }
 
-    th_propagation::th_propagation(unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs, sat::literal c, enode_pair const& p) {
+    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) {
         m_consequent = c;
         m_eq = p;
         m_num_literals = n_lits;
         m_num_eqs = n_eqs;
-        m_literals = reinterpret_cast<literal*>(reinterpret_cast<char*>(this) + sizeof(th_propagation));
+        m_literals = reinterpret_cast<literal*>(reinterpret_cast<char*>(this) + sizeof(th_explain));
         for (unsigned i = 0; i < n_lits; ++i)
             m_literals[i] = lits[i];
-        m_eqs = reinterpret_cast<enode_pair*>(reinterpret_cast<char*>(this) + sizeof(th_propagation) + sizeof(literal) * n_lits);
+        m_eqs = reinterpret_cast<enode_pair*>(reinterpret_cast<char*>(this) + sizeof(th_explain) + sizeof(literal) * n_lits);
         for (unsigned i = 0; i < n_eqs; ++i)
             m_eqs[i] = eqs[i];       
  
     }
 
-    th_propagation* th_propagation::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_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) {
         region& r = th.ctx.get_region();
         void* mem = r.allocate(get_obj_size(n_lits, n_eqs));
         sat::constraint_base::initialize(mem, &th);
-        return new (sat::constraint_base::ptr2mem(mem)) th_propagation(n_lits, lits, n_eqs, eqs, c, enode_pair(x, y));
+        return new (sat::constraint_base::ptr2mem(mem)) th_explain(n_lits, lits, n_eqs, eqs, c, enode_pair(x, y));
     }
 
-    th_propagation* th_propagation::propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, sat::literal consequent) {
+    th_explain* th_explain::propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, sat::literal consequent) {
         return mk(th, lits.size(), lits.c_ptr(), eqs.size(), eqs.c_ptr(), consequent, nullptr, nullptr);
     }
 
-    th_propagation* th_propagation::propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, euf::enode* x, euf::enode* y) {
+    th_explain* th_explain::propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, euf::enode* x, euf::enode* y) {
         return mk(th, lits.size(), lits.c_ptr(), eqs.size(), eqs.c_ptr(), sat::null_literal, x, y);
     }
 
-    th_propagation* th_propagation::propagate(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y) {
+    th_explain* th_explain::propagate(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y) {
         return mk(th, 1, &lit, 0, nullptr, sat::null_literal, x, y);
     }
 
-    th_propagation* th_propagation::conflict(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs) {
+    th_explain* th_explain::conflict(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs) {
         return conflict(th, lits.size(), lits.c_ptr(), eqs.size(), eqs.c_ptr());
     }
 
-    th_propagation* th_propagation::conflict(th_euf_solver& th, unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs) {
+    th_explain* th_explain::conflict(th_euf_solver& th, unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs) {
         return mk(th, n_lits, lits, n_eqs, eqs, sat::null_literal, nullptr, nullptr);
     }
 
-    th_propagation* th_propagation::conflict(th_euf_solver& th, enode_pair_vector const& eqs) {
+    th_explain* th_explain::conflict(th_euf_solver& th, enode_pair_vector const& eqs) {
         return conflict(th, 0, nullptr, eqs.size(), eqs.c_ptr());
     }
 
-    th_propagation* th_propagation::conflict(th_euf_solver& th, sat::literal lit) {
+    th_explain* th_explain::conflict(th_euf_solver& th, sat::literal lit) {
         return conflict(th, 1, &lit, 0, nullptr);
     }
 
-    th_propagation* th_propagation::conflict(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y) {
+    th_explain* th_explain::conflict(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y) {
         enode_pair eq(x, y);
         return conflict(th, 1, &lit, 1, &eq);
     }
 
-    th_propagation* th_propagation::conflict(th_euf_solver& th, euf::enode* x, euf::enode* y) {
+    th_explain* th_explain::conflict(th_euf_solver& th, euf::enode* x, euf::enode* y) {
         enode_pair eq(x, y);
         return conflict(th, 0, nullptr, 1, &eq);
     }
 
-    std::ostream& th_propagation::display(std::ostream& out) const {
+    std::ostream& th_explain::display(std::ostream& out) const {
-        for (auto lit : euf::th_propagation::lits(*this))
+        for (auto lit : euf::th_explain::lits(*this))
             out << lit << " ";
-        for (auto eq : euf::th_propagation::eqs(*this))
+        for (auto eq : euf::th_explain::eqs(*this))
             out << eq.first->get_expr_id() << " == " << eq.second->get_expr_id() << " ";
         if (m_consequent != sat::null_literal)
             out << "--> " << m_consequent;

src/sat/smt/sat_th.h

@@ -165,7 +165,7 @@ namespace euf {
             for (; m_num_scopes > 0; --m_num_scopes) push_core();
         }
 
-        friend class th_propagation;
+        friend class th_explain;
 
     public:
         th_euf_solver(euf::solver& ctx, symbol const& name, euf::theory_id id);
@@ -191,36 +191,41 @@ namespace euf {
         unsigned random();
     };
 
-
+    /**
-    class th_propagation {
+    * General purpose, eager explanation object. Explanations are conjunctions of literals and equalities.
-        sat::literal   m_consequent { sat::null_literal };
+    * Used literals and equalities are stored in the object and retrieved on demand for conflict resolution
-        enode_pair     m_eq { enode_pair() };
+    * It is "eager" in the sense that relevant literals are accumulated when the explanation is created.
+    * This is not a real problem for conflicts, but a theory has an option to implement custom lazy explanations
+    * that retrieve literals on demand.
+    */
+    class th_explain {
+        sat::literal   m_consequent { sat::null_literal }; // literal consequent for propagations
+        enode_pair     m_eq { enode_pair() };              // equality consequent for propagations
         unsigned       m_num_literals;
         unsigned       m_num_eqs;        
         sat::literal*  m_literals;
         enode_pair*    m_eqs;
         static size_t get_obj_size(unsigned num_lits, unsigned num_eqs);
-        th_propagation(unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs, sat::literal c, enode_pair const& eq);
+        th_explain(unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs, sat::literal c, enode_pair const& eq);
-        static th_propagation* 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);
+        static 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);
 
     public:
-        static th_propagation* conflict(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs);
+        static th_explain* conflict(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs);
-        static th_propagation* conflict(th_euf_solver& th, sat::literal_vector const& lits) { return conflict(th, lits.size(), lits.c_ptr(), 0, nullptr); }
+        static th_explain* conflict(th_euf_solver& th, sat::literal_vector const& lits) { return conflict(th, lits.size(), lits.c_ptr(), 0, nullptr); }
-        static th_propagation* conflict(th_euf_solver& th, unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs);
+        static th_explain* conflict(th_euf_solver& th, unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs);
-        static th_propagation* conflict(th_euf_solver& th, enode_pair_vector const& eqs);
+        static th_explain* conflict(th_euf_solver& th, enode_pair_vector const& eqs);
-        static th_propagation* conflict(th_euf_solver& th, sat::literal lit);
+        static th_explain* conflict(th_euf_solver& th, sat::literal lit);
-        static th_propagation* conflict(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y);
+        static th_explain* conflict(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y);
-        static th_propagation* conflict(th_euf_solver& th, euf::enode* x, euf::enode* y);
+        static th_explain* conflict(th_euf_solver& th, euf::enode* x, euf::enode* y);
-        static th_propagation* propagate(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y);
+        static th_explain* propagate(th_euf_solver& th, sat::literal lit, euf::enode* x, euf::enode* y);
-        static th_propagation* propagate(th_euf_solver& th, unsigned n_lits, sat::literal const* lits, unsigned n_eqs, enode_pair const* eqs, sat::literal consequent);
+        static th_explain* propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, sat::literal consequent);
-        static th_propagation* propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, sat::literal consequent);
+        static th_explain* propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, euf::enode* x, euf::enode* y);
-        static th_propagation* propagate(th_euf_solver& th, sat::literal_vector const& lits, enode_pair_vector const& eqs, euf::enode* x, euf::enode* y);
 
         sat::ext_constraint_idx to_index() const {
             return sat::constraint_base::mem2base(this);
         }
-        static th_propagation& from_index(size_t idx) {
+        static th_explain& from_index(size_t idx) {
-            return *reinterpret_cast<th_propagation*>(sat::constraint_base::from_index(idx)->mem());
+            return *reinterpret_cast<th_explain*>(sat::constraint_base::from_index(idx)->mem());
         }
 
         sat::extension& ext() const {
@@ -230,17 +235,17 @@ namespace euf {
         std::ostream& display(std::ostream& out) const;
 
         class lits {
-            th_propagation const& th;
+            th_explain const& th;
         public:
-            lits(th_propagation const& th) : th(th) {}
+            lits(th_explain const& th) : th(th) {}
             sat::literal const* begin() const { return th.m_literals; }
             sat::literal const* end() const { return th.m_literals + th.m_num_literals; }
         };
 
         class eqs {
-            th_propagation const& th;
+            th_explain const& th;
         public:
-            eqs(th_propagation const& th) : th(th) {}
+            eqs(th_explain const& th) : th(th) {}
             enode_pair const* begin() const { return th.m_eqs; }
             enode_pair const* end() const { return th.m_eqs + th.m_num_eqs; }
         };