updates to ac-plugin

fix incrementality bugs by allowing destructive updates during saturation at the cost of redoing saturation after a pop.

src/ast/euf/euf_ac_plugin.cpp

@@ -136,15 +136,13 @@ namespace euf {
 
     // unit -> {}
     void ac_plugin::add_unit(enode* u) {
-        m_units.push_back(u);
+        push_equation(u, nullptr);
-        mk_node(u);
-        auto m_id = to_monomial(u, {});
-        init_equation(eq(to_monomial(u), m_id, justification::axiom(get_id())));
     }
 
     // zero x -> zero
     void ac_plugin::add_zero(enode* z) {
         mk_node(z)->is_zero = true;
+        // zeros persist
     }
 
     void ac_plugin::register_shared(enode* n) {
@@ -165,12 +163,16 @@ namespace euf {
         push_undo(is_register_shared);
     }
 
+    void ac_plugin::push_scope_eh() {
+        push_undo(is_push_scope);
+    }
+
     void ac_plugin::undo() {
         auto k = m_undo.back();
         m_undo.pop_back();
         switch (k) {
-        case is_add_eq: {
+        case is_queue_eq: {
-            m_active.pop_back();
+            m_queued.pop_back();
             break;
         }
         case is_add_node: {
@@ -180,14 +182,15 @@ namespace euf {
             n->~node();
             break;
         }
-        case is_add_monomial: {
+        case is_push_scope: {
-            m_monomials.pop_back();
+            m_active.reset();
+            m_passive.reset();
+            m_units.reset();
+            m_queue_head = 0;
             break;
         }
-        case is_update_eq: {
+        case is_add_monomial: {
-            auto const& [idx, eq] = m_update_eq_trail.back();
+            m_monomials.pop_back();
-            m_active[idx] = eq;
-            m_update_eq_trail.pop_back();
             break;
         }
         case is_add_shared_index: {
@@ -316,14 +319,24 @@ namespace euf {
     }
 
     void ac_plugin::merge_eh(enode* l, enode* r) {
-        if (l == r)
+        push_equation(l, r);
-            return;
+    }
+
+    void ac_plugin::pop_equation(enode* l, enode* r) {
         m_fuel += m_fuel_inc;
-        auto j = justification::equality(l, r);
+        if (!r) {
-        auto m1 = to_monomial(l);
+            m_units.push_back(l);
-        auto m2 = to_monomial(r);
+            mk_node(l);
-        TRACE(plugin, tout << "merge: " << m_name << " " << g.bpp(l) << " == " << g.bpp(r) << " " << m_pp_ll(*this, monomial(m1)) << " == " << m_pp_ll(*this, monomial(m2)) << "\n");
+            auto m_id = to_monomial(l, {});
-        init_equation(eq(m1, m2, j));
+            init_equation(eq(to_monomial(l), m_id, justification::axiom(get_id())), true);
+        }
+        else {
+            auto j = justification::equality(l, r);
+            auto m1 = to_monomial(l);
+            auto m2 = to_monomial(r);
+            TRACE(plugin, tout << "merge: " << m_name << " " << g.bpp(l) << " == " << g.bpp(r) << " " << m_pp_ll(*this, monomial(m1)) << " == " << m_pp_ll(*this, monomial(m2)) << "\n");
+            init_equation(eq(m1, m2, j), true);
+        }
     }
 
     void ac_plugin::diseq_eh(enode* eq) {
@@ -336,64 +349,83 @@ namespace euf {
         register_shared(b);
     }
 
-    bool ac_plugin::init_equation(eq const& e) {
+    void ac_plugin::push_equation(enode* l, enode* r) {
-        m_active.push_back(e);
+        if (l == r)
-        auto& eq = m_active.back();
+            return;
-        deduplicate(monomial(eq.l).m_nodes, monomial(eq.r).m_nodes);
+        m_queued.push_back({ l, r });
+        push_undo(is_queue_eq);
+    }
 
-        if (orient_equation(eq)) {
+    bool ac_plugin::init_equation(eq eq, bool is_active) {
-            auto& ml = monomial(eq.l);
+        deduplicate(monomial(eq.l), monomial(eq.r));
-            auto& mr = monomial(eq.r);
+        if (!orient_equation(eq))
+            return false;
 
-            unsigned eq_id = m_active.size() - 1;
+#if 0
+        if (is_reducing(eq))
+            is_active = true;
+#endif
 
-            if (ml.size() == 1 && mr.size() == 1)
+        is_active = true; // set to active because forward reduction is not implemented yet.
-                push_merge(ml[0]->n, mr[0]->n, eq.j);
+        // we will have to forward reduce a passive equation before it can be activated.
-          
+        // this means that we have to iterate over all overlaps of variables in equation with
-            for (auto n : ml) {
+        // reducing eqations. Otherwise, we will not have the invariant that reducing variables
-                if (!n->n->is_marked2()) {
+        // are eliminated from all equations.
-                    n->eqs.push_back(eq_id);
-                    n->n->mark2();
-                    push_undo(is_add_eq_index);
-                    m_node_trail.push_back(n);
-                    for (auto s : n->shared)
-                        m_shared_todo.insert(s);
-                }
-            }
-
-            for (auto n : mr) {
-                if (!n->n->is_marked2()) {
-                    n->eqs.push_back(eq_id);
-                    n->n->mark2();
-                    push_undo(is_add_eq_index);
-                    m_node_trail.push_back(n);
-                    for (auto s : n->shared)
-                        m_shared_todo.insert(s);
-                }
-            }
-
-            for (auto n : ml) 
-                n->n->unmark2();
-
-            for (auto n : mr)
-                n->n->unmark2();
-
-            SASSERT(well_formed(eq));
-
-            TRACE(plugin, display_equation_ll(tout, eq) << " shared: " << m_shared_todo << "\n");
-            m_to_simplify_todo.insert(eq_id);
-            m_new_eqs.push_back(eq_id);
-
-            //display_equation_ll(verbose_stream() << "init " << eq_id << ": ", eq) << "\n";
 
+        if (!is_active) {
+            m_passive.push_back(eq);
             return true;          
         }
-        else {
+
-            m_active.pop_back();
+        m_active.push_back(eq);
-            return false;
+        auto& ml = monomial(eq.l);
+        auto& mr = monomial(eq.r);
+
+        unsigned eq_id = m_active.size() - 1;
+
+        if (ml.size() == 1 && mr.size() == 1)
+            push_merge(ml[0]->n, mr[0]->n, eq.j);
+
+        for (auto n : ml) {
+            if (!n->n->is_marked2()) {
+                n->eqs.push_back(eq_id);
+                n->n->mark2();
+                push_undo(is_add_eq_index);
+                m_node_trail.push_back(n);
+                for (auto s : n->shared)
+                    m_shared_todo.insert(s);
+            }
         }
+
+        for (auto n : mr) {
+            if (!n->n->is_marked2()) {
+                n->eqs.push_back(eq_id);
+                n->n->mark2();
+                push_undo(is_add_eq_index);
+                m_node_trail.push_back(n);
+                for (auto s : n->shared)
+                    m_shared_todo.insert(s);
+            }
+        }
+
+        for (auto n : ml)
+            n->n->unmark2();
+
+        for (auto n : mr)
+            n->n->unmark2();
+
+        SASSERT(well_formed(eq));
+
+        TRACE(plugin, display_equation_ll(tout, eq) << " shared: " << m_shared_todo << "\n");
+        m_to_simplify_todo.insert(eq_id);
+        m_new_eqs.push_back(eq_id);
+
+        //display_equation_ll(verbose_stream() << "init " << eq_id << ": ", eq) << "\n";
+
+        return true;
     }
     
+
     bool ac_plugin::orient_equation(eq& e) {
         auto& ml = monomial(e.l);
         auto& mr = monomial(e.r);
@@ -429,7 +461,7 @@ namespace euf {
                 return false;
             if (!is_sorted(mr))
                 return false;
-            for (unsigned i = 0; i < ml.size();  ++i) {
+            for (unsigned i = 0; i < ml.size(); ++i) {
                 if (ml[i]->id() == mr[i]->id())
                     continue;
                 if (ml[i]->id() < mr[i]->id())
@@ -455,15 +487,21 @@ namespace euf {
 
     uint64_t ac_plugin::filter(monomial_t& m) {
         auto& bloom = m.m_bloom;
-        if (bloom.m_tick == m_tick)
+
+        if (bloom.m_tick == m_tick) {
+            uint64_t f = 0;
+            for (auto n : m)
+                f |= (1ull << (n->id() % 64ull));
+            SASSERT(f == bloom.m_filter);
             return bloom.m_filter;
+        }
         bloom.m_filter = 0;
         for (auto n : m)
             bloom.m_filter |= (1ull << (n->id() % 64ull));
         if (!is_sorted(m))
             sort(m);
         bloom.m_tick = m_tick;
-        return bloom.m_filter;
+         return bloom.m_filter;
     }
 
     bool ac_plugin::can_be_subset(monomial_t& subset, monomial_t& superset) {
@@ -562,6 +600,10 @@ namespace euf {
     }
 
     void ac_plugin::propagate() {
+        while (m_queue_head < m_queued.size()) {
+            auto [l, r] = m_queued[m_queue_head++];
+            pop_equation(l, r);
+        }
         while (true) {
         loop_start:
             if (m_fuel == 0)
@@ -576,14 +618,14 @@ namespace euf {
 
             // simplify eq using processed
             TRACE(plugin,
-                  for (auto other_eq : forward_iterator(eq_id))
+                for (auto other_eq : forward_iterator(eq_id))
-                      tout << "forward iterator " << eq_id << " vs " << other_eq << " " << is_processed(other_eq) << "\n");
+                    tout << "forward iterator " << eq_id << " vs " << other_eq << " " << is_processed(other_eq) << "\n");
             for (auto other_eq : forward_iterator(eq_id))
                 if (is_processed(other_eq) && forward_simplify(eq_id, other_eq))
                     goto loop_start;
 
             auto& eq = m_active[eq_id];
-            deduplicate(monomial(eq.l).m_nodes, monomial(eq.r).m_nodes);
+            deduplicate(monomial(eq.l), monomial(eq.r));
             if (monomial(eq.l).size() == 0) {
                 set_status(eq_id, eq_status::is_dead_eq);
                 continue;
@@ -623,12 +665,20 @@ namespace euf {
     }
 
     unsigned ac_plugin::pick_next_eq() {
+        init_pick:
         while (!m_to_simplify_todo.empty()) {
             unsigned id = *m_to_simplify_todo.begin();
             if (id < m_active.size() && is_to_simplify(id))
                 return id;
             m_to_simplify_todo.remove(id);
         }
+        if (!m_passive.empty()) {
+            auto eq = m_passive.back();
+            verbose_stream() << "pick passive " << eq_pp_ll(*this, eq) << "\n";
+            m_passive.pop_back();
+            init_equation(eq, true);
+            goto init_pick;
+        }
         return UINT_MAX;
     }
 
@@ -640,11 +690,7 @@ namespace euf {
         if (are_equal(monomial(eq.l), monomial(eq.r)))
             s = eq_status::is_dead_eq;
 
-        if (eq.status != s) {
+        eq.status = s;
-            m_update_eq_trail.push_back({ id, eq });
-            eq.status = s;
-            push_undo(is_update_eq);
-        }
         switch (s) {
         case eq_status::is_processed_eq:
         case eq_status::is_reducing_eq:
@@ -673,7 +719,7 @@ namespace euf {
     }
 
     //
-    // backward iterator allows simplification of eq
+    // forward iterator allows simplification of eq
     // The rhs of eq is a super-set of lhs of other eq.
     // 
     unsigned_vector const& ac_plugin::forward_iterator(unsigned eq_id) {
@@ -749,7 +795,7 @@ namespace euf {
     }
 
     //
-    // forward iterator simplifies other eqs where their rhs is a superset of lhs of eq
+    // backward iterator simplifies other eqs where their rhs is a superset of lhs of eq
     // 
     unsigned_vector const& ac_plugin::backward_iterator(unsigned eq_id) {
         auto& eq = m_active[eq_id];
@@ -786,7 +832,7 @@ namespace euf {
         init_ref_counts(m, check);
         return
             all_of(counts, [&](unsigned i) { return check[i] == counts[i]; }) &&
-            all_of(check,  [&](unsigned i) { return check[i] == counts[i]; });
+            all_of(check, [&](unsigned i) { return check[i] == counts[i]; });
     }
 
     void ac_plugin::backward_simplify(unsigned src_eq, unsigned dst_eq) {
@@ -843,10 +889,8 @@ namespace euf {
         reduce(m_src_r, j);
         auto new_r = to_monomial(m_src_r);
         index_new_r(dst_eq, monomial(m_active[dst_eq].r), monomial(new_r));
-        m_update_eq_trail.push_back({ dst_eq, m_active[dst_eq] });
         m_active[dst_eq].r = new_r;
         m_active[dst_eq].j = j;
-        push_undo(is_update_eq);
         m_src_r.reset();
         m_src_r.append(monomial(src.r).m_nodes);
         TRACE(plugin_verbose, tout << "rewritten to " << m_pp_ll(*this, monomial(new_r)) << "\n");
@@ -862,7 +906,7 @@ namespace euf {
         //
         // dst_ids, dst_count contain rhs of dst_eq
         //
-        TRACE(plugin, tout << "backward simplify " << eq_pp_ll(*this, src) << " " << eq_pp_ll(*this, dst) << " can-be-subset: " << can_be_subset(monomial(src.l), monomial(dst.r)) << "\n");
+        TRACE(plugin, tout << "forward simplify " << eq_pp_ll(*this, src) << " " << eq_pp_ll(*this, dst) << " can-be-subset: " << can_be_subset(monomial(src.l), monomial(dst.r)) << "\n");
 
         if (forward_subsumes(src_eq, dst_eq)) {
             set_status(dst_eq, eq_status::is_dead_eq);
@@ -891,11 +935,9 @@ namespace euf {
         reduce(m, j);
         auto new_r = to_monomial(m);
         index_new_r(dst_eq, monomial(m_active[dst_eq].r), monomial(new_r));
-        m_update_eq_trail.push_back({ dst_eq, m_active[dst_eq] });
         m_active[dst_eq].r = new_r;
         m_active[dst_eq].j = j;
         TRACE(plugin, tout << "rewritten to " << m_pp(*this, monomial(new_r)) << "\n");
-        push_undo(is_update_eq);
 
         return true;
     }
@@ -913,7 +955,7 @@ namespace euf {
         m_new_eqs.reset();
     }
 
-    bool ac_plugin::is_forward_subsumed(unsigned eq_id)  {
+    bool ac_plugin::is_forward_subsumed(unsigned eq_id) {
         return any_of(forward_iterator(eq_id), [&](unsigned other_eq) { return forward_subsumes(other_eq, eq_id); });
     }
 
@@ -975,7 +1017,9 @@ namespace euf {
             SASSERT(!are_equal(m_active[src_eq], m_active[dst_eq]));
             return false;
         }
-        return all_of(monomial(dst.r), [&](node* n) { unsigned id = n->id(); return m_src_r_counts[id] == m_dst_r_counts[id]; });
+        bool r = all_of(monomial(dst.r), [&](node* n) { unsigned id = n->id(); return m_src_r_counts[id] == m_dst_r_counts[id]; });
+        SASSERT(r || !are_equal(m_active[src_eq], m_active[dst_eq]));
+        return r;
     }
 
     // src_l_counts, src_r_counts are initialized for src.l, src.r
@@ -1079,8 +1123,7 @@ namespace euf {
                     goto init_loop;
                 }
             }
-        }
+        } while (false);
-        while (false);
         VERIFY(sz >= m.size());
         return change;
     }
@@ -1122,7 +1165,7 @@ namespace euf {
         auto& src = m_active[src_eq];
         auto& dst = m_active[dst_eq];
 
-        unsigned max_left  = std::max(monomial(src.l).size(), monomial(dst.l).size());
+        unsigned max_left = std::max(monomial(src.l).size(), monomial(dst.l).size());
         unsigned min_right = std::max(monomial(src.r).size(), monomial(dst.r).size());
 
 
@@ -1177,11 +1220,11 @@ namespace euf {
         unsigned max_left_new = std::max(m_src_r.size(), m_dst_r.size());
         unsigned min_right_new = std::min(m_src_r.size(), m_dst_r.size());
         if (max_left_new <= max_left && min_right_new <= min_right)
-            added_eq = init_equation(eq(to_monomial(m_src_r), to_monomial(m_dst_r), j));
+            added_eq = init_equation(eq(to_monomial(m_src_r), to_monomial(m_dst_r), j), false);
 
         CTRACE(plugin, added_eq,
             tout << "superpose: " << m_name << " " << eq_pp_ll(*this, src) << " " << eq_pp_ll(*this, dst) << " --> ";
-            tout << m_pp_ll(*this, m_src_r) << "== " << m_pp_ll(*this, m_dst_r) << "\n";);
+        tout << m_pp_ll(*this, m_src_r) << "== " << m_pp_ll(*this, m_dst_r) << "\n";);
 
         m_src_r.reset();
         m_src_r.append(monomial(src_r).m_nodes);
@@ -1204,21 +1247,24 @@ namespace euf {
         }
     }
 
-    // TODO: this is destructive. It breaks reversibility.
-    // TODO: also need justifications from eq if there is a change.
     void ac_plugin::backward_reduce(eq const& eq, unsigned other_eq_id) {
         auto& other_eq = m_active[other_eq_id];
+        TRACE(plugin_verbose,
+            tout << "backward reduce " << eq_pp_ll(*this, eq) << " " << eq_pp_ll(*this, other_eq) << "\n");
         bool change = false;
-        if (backward_reduce_monomial(eq, monomial(other_eq.l)))
+        if (backward_reduce_monomial(eq, other_eq, monomial(other_eq.l)))
             change = true;
-        if (backward_reduce_monomial(eq, monomial(other_eq.r)))
+        if (backward_reduce_monomial(eq, other_eq, monomial(other_eq.r)))
             change = true;
-        if (change) 
+        CTRACE(plugin, change,
+            tout << "backward reduce " << eq_pp_ll(*this, eq) << " " << eq_pp_ll(*this, other_eq) << "\n");
+        if (change) {
             set_status(other_eq_id, eq_status::is_to_simplify_eq);
+        }
     }
 
-    bool ac_plugin::backward_reduce_monomial(eq const& eq, monomial_t& m) {
+    bool ac_plugin::backward_reduce_monomial(eq const& src, eq& dst, monomial_t& m) {
-        auto const& r = monomial(eq.r);
+        auto const& r = monomial(src.r);
         unsigned j = 0;
         bool change = false;
         for (auto n : m) {
@@ -1241,6 +1287,10 @@ namespace euf {
             m.m_nodes[j++] = r[0];
         }
         m.m_nodes.shrink(j);
+        if (change) {
+            m.m_bloom.m_tick = 0;
+            dst.j = join(dst.j, src);
+        }
         return change;
     }
 
@@ -1277,21 +1327,29 @@ namespace euf {
         return true;
     }
 
+
+    void ac_plugin::deduplicate(monomial_t& a, monomial_t& b) {
+        unsigned sza = a.size(), szb = b.size();
+        deduplicate(a.m_nodes, b.m_nodes);
+        if (sza != a.size())
+            a.m_bloom.m_tick = 0;
+        if (szb != b.size())
+            b.m_bloom.m_tick = 0;
+    }
+
     void ac_plugin::deduplicate(ptr_vector<node>& a, ptr_vector<node>& b) {
-        {
+        for (auto n : a) {
-            for (auto n : a) {
+            if (n->is_zero) {
-                if (n->is_zero) {
+                a[0] = n;
-                     a[0] = n;
+                a.shrink(1);
-                    a.shrink(1);
+                break;
-                    break;
-                }
             }
-            for (auto n : b) {
+        }
-                if (n->is_zero) {
+        for (auto n : b) {
-                    b[0] = n;
+            if (n->is_zero) {
-                    b.shrink(1);
+                b[0] = n;
-                    break;
+                b.shrink(1);
-                }
+                break;
             }
         }
 
@@ -1385,9 +1443,7 @@ namespace euf {
         push_undo(is_update_shared);
         m_shared[idx].m = new_m;
         m_shared[idx].j = j;
-
         TRACE(plugin_verbose, tout << "shared simplified to " << m_pp_ll(*this, monomial(new_m)) << "\n");
-        
         push_merge(old_n, new_n, j);
     }
 
@@ -1397,19 +1453,15 @@ namespace euf {
     }
 
     justification::dependency* ac_plugin::justify_equation(unsigned eq) {
-        auto const& e = m_active[eq];
+        return m_dep_manager.mk_leaf(m_active[eq].j);
-        auto* j = m_dep_manager.mk_leaf(e.j);
-        j = justify_monomial(j, monomial(e.l));
-        j = justify_monomial(j, monomial(e.r));
-        return j;
-    }
-
-    justification::dependency* ac_plugin::justify_monomial(justification::dependency* j, monomial_t const& m) {
-        return j;
     }
 
     justification ac_plugin::join(justification j, unsigned eq) {
         return justification::dependent(m_dep_manager.mk_join(m_dep_manager.mk_leaf(j), justify_equation(eq)));
     }
 
+    justification ac_plugin::join(justification j, eq const& eq) {
+        return justification::dependent(m_dep_manager.mk_join(m_dep_manager.mk_leaf(j), m_dep_manager.mk_leaf(eq.j)));
+    }
+
 }

src/ast/euf/euf_ac_plugin.h

@@ -123,6 +123,7 @@ namespace euf {
         func_decl*               m_decl = nullptr;
         bool                     m_is_injective = false;
         vector<eq>               m_active, m_passive;
+        enode_pair_vector        m_queued;
         ptr_vector<node>         m_nodes;
         bool_vector              m_shared_nodes;
         vector<monomial_t>       m_monomials;
@@ -146,21 +147,21 @@ namespace euf {
 
         // backtrackable state
         enum undo_kind {
-            is_add_eq,
+            is_queue_eq,
             is_add_monomial,
             is_add_node,
-            is_update_eq,
             is_add_shared_index,
             is_add_eq_index,
             is_register_shared,
-            is_update_shared
+            is_update_shared,
+            is_push_scope
         };
         svector<undo_kind>       m_undo;
         ptr_vector<node>         m_node_trail;
+        unsigned                 m_queue_head = 0;
 
         svector<std::pair<unsigned, shared>> m_update_shared_trail;
         svector<std::tuple<node*, unsigned, unsigned>> m_merge_trail;
-        svector<std::pair<unsigned, eq>> m_update_eq_trail;
 
 
 
@@ -191,8 +192,8 @@ namespace euf {
         bool well_formed(eq const& e) const;
         bool is_reducing(eq const& e) const;
         void backward_reduce(unsigned eq_id);
-        void backward_reduce(eq const& src, unsigned dst);
+        void backward_reduce(eq const& eq, unsigned dst);
-        bool backward_reduce_monomial(eq const& eq, monomial_t& m);
+        bool backward_reduce_monomial(eq const& src, eq & dst, monomial_t& m);
         void forward_subsume_new_eqs();
         bool is_forward_subsumed(unsigned dst_eq);
         bool forward_subsumes(unsigned src_eq, unsigned dst_eq);
@@ -208,7 +209,9 @@ namespace euf {
             return nullptr;
         }
        
-        bool init_equation(eq const& e);
+        bool init_equation(eq e, bool is_active);
+        void push_equation(enode* l, enode* r);
+        void pop_equation(enode* l, enode* r);
         bool orient_equation(eq& e);
         void set_status(unsigned eq_id, eq_status s);
         unsigned pick_next_eq();
@@ -217,6 +220,7 @@ namespace euf {
         void backward_simplify(unsigned eq_id, unsigned using_eq);
         bool forward_simplify(unsigned eq_id, unsigned using_eq);
         bool superpose(unsigned src_eq, unsigned dst_eq);
+        void deduplicate(monomial_t& a, monomial_t& b);
         void deduplicate(ptr_vector<node>& a, ptr_vector<node>& b);
         
         ptr_vector<node> m_src_r, m_src_l, m_dst_r, m_dst_l;
@@ -260,8 +264,8 @@ namespace euf {
 
         justification justify_rewrite(unsigned eq1, unsigned eq2);
         justification::dependency* justify_equation(unsigned eq);
-        justification::dependency* justify_monomial(justification::dependency* d, monomial_t const& m);
         justification join(justification j1, unsigned eq);
+        justification join(justification j1, eq const& eq);
 
         bool is_correct_ref_count(monomial_t const& m, ref_counts const& counts) const;
         bool is_correct_ref_count(ptr_vector<node> const& m, ref_counts const& counts) const;
@@ -301,6 +305,8 @@ namespace euf {
 
         void undo() override;
 
+        void push_scope_eh() override;
+
         void propagate() override;
         
         std::ostream& display(std::ostream& out) const override;

src/ast/euf/euf_arith_plugin.h

@@ -43,6 +43,11 @@ namespace euf {
 
         void undo() override;
 
+        void push_scope_eh() override {
+            m_add.push_scope_eh();
+            m_mul.push_scope_eh();
+        }
+
         void propagate() override;
         
         std::ostream& display(std::ostream& out) const override;

src/ast/euf/euf_egraph.cpp

@@ -103,6 +103,9 @@ namespace euf {
             m_scopes.push_back(m_updates.size());
             m_region.push_scope();
             m_updates.push_back(update_record(m_new_th_eqs_qhead, update_record::new_th_eq_qhead()));
+            for (auto p : m_plugins)
+                if (p)
+                    p->push_scope_eh();
         }
         SASSERT(m_new_th_eqs_qhead <= m_new_th_eqs.size());
     }

src/ast/euf/euf_plugin.h

@@ -53,6 +53,8 @@ namespace euf {
 
         virtual void undo() = 0;
 
+        virtual void push_scope_eh() {}
+        
         virtual std::ostream& display(std::ostream& out) const = 0;
 
         virtual void collect_statistics(statistics& st) const {}