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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,242 @@ | ||
| /*++ | ||
| Copyright (c) 2020 Microsoft Corporation | ||
| Module Name: | ||
| euf_internalize.cpp | ||
| Abstract: | ||
| Internalize utilities for EUF solver plugin. | ||
| Author: | ||
| Nikolaj Bjorner (nbjorner) 2020-08-25 | ||
| --*/ | ||
|
|
||
| #include "ast/ast_pp.h" | ||
| #include "ast/pb_decl_plugin.h" | ||
| #include "tactic/tactic_exception.h" | ||
| #include "sat/smt/euf_solver.h" | ||
|
|
||
| namespace euf { | ||
|
|
||
| sat::literal solver::internalize(expr* e, bool sign, bool root, bool learned) { | ||
| flet<bool> _is_learned(m_is_redundant, learned); | ||
| auto* ext = get_solver(e); | ||
| if (ext) | ||
| return ext->internalize(e, sign, root, learned); | ||
| IF_VERBOSE(110, verbose_stream() << "internalize: " << mk_pp(e, m) << "\n"); | ||
| SASSERT(!si.is_bool_op(e)); | ||
| sat::scoped_stack _sc(m_stack); | ||
| unsigned sz = m_stack.size(); | ||
| euf::enode* n = visit(e); | ||
| while (m_stack.size() > sz) { | ||
| loop: | ||
| if (!m.inc()) | ||
| throw tactic_exception(m.limit().get_cancel_msg()); | ||
| sat::frame & fr = m_stack.back(); | ||
| expr* e = fr.m_e; | ||
| if (m_egraph.find(e)) { | ||
| m_stack.pop_back(); | ||
| continue; | ||
| } | ||
| unsigned num = is_app(e) ? to_app(e)->get_num_args() : 0; | ||
|
|
||
| while (fr.m_idx < num) { | ||
| expr* arg = to_app(e)->get_arg(fr.m_idx); | ||
| fr.m_idx++; | ||
| n = visit(arg); | ||
| if (!n) | ||
| goto loop; | ||
| } | ||
| m_args.reset(); | ||
| for (unsigned i = 0; i < num; ++i) | ||
| m_args.push_back(m_egraph.find(to_app(e)->get_arg(i))); | ||
| if (root && internalize_root(to_app(e), m_args.c_ptr(), sign)) | ||
| return sat::null_literal; | ||
| n = m_egraph.mk(e, num, m_args.c_ptr()); | ||
| attach_node(n); | ||
| } | ||
| SASSERT(m_egraph.find(e)); | ||
| return literal(m_expr2var.to_bool_var(e), sign); | ||
| } | ||
|
|
||
| euf::enode* solver::visit(expr* e) { | ||
| euf::enode* n = m_egraph.find(e); | ||
| if (n) | ||
| return n; | ||
| if (si.is_bool_op(e)) { | ||
| sat::literal lit = si.internalize(e, m_is_redundant); | ||
| n = m_var2node.get(lit.var(), nullptr); | ||
| if (n && !lit.sign()) | ||
| return n; | ||
|
|
||
| n = m_egraph.mk(e, 0, nullptr); | ||
| attach_lit(lit, n); | ||
| if (!m.is_true(e) && !m.is_false(e)) | ||
| s().set_external(lit.var()); | ||
| return n; | ||
| } | ||
| if (is_app(e) && to_app(e)->get_num_args() > 0) { | ||
| m_stack.push_back(sat::frame(e)); | ||
| return nullptr; | ||
| } | ||
| n = m_egraph.mk(e, 0, nullptr); | ||
| attach_node(n); | ||
| return n; | ||
| } | ||
|
|
||
| void solver::attach_node(euf::enode* n) { | ||
| expr* e = n->get_owner(); | ||
| if (m.is_bool(e)) { | ||
| sat::bool_var v = si.add_bool_var(e); | ||
| attach_lit(literal(v, false), n); | ||
| } | ||
| axiomatize_basic(n); | ||
| } | ||
|
|
||
| void solver::attach_lit(literal lit, euf::enode* n) { | ||
| if (lit.sign()) { | ||
| sat::bool_var v = si.add_bool_var(n->get_owner()); | ||
| sat::literal lit2 = literal(v, false); | ||
| s().mk_clause(~lit, lit2, false); | ||
| s().mk_clause(lit, ~lit2, false); | ||
| lit = lit2; | ||
| } | ||
| sat::bool_var v = lit.var(); | ||
| m_var2node.reserve(v + 1, nullptr); | ||
| SASSERT(m_var2node[v] == nullptr); | ||
| m_var2node[v] = n; | ||
| m_var_trail.push_back(v); | ||
| } | ||
|
|
||
| bool solver::internalize_root(app* e, enode* const* args, bool sign) { | ||
| if (m.is_distinct(e)) { | ||
| if (sign) | ||
| add_not_distinct_axiom(e, args); | ||
| else | ||
| add_distinct_axiom(e, args); | ||
| return true; | ||
| } | ||
| return false; | ||
| } | ||
|
|
||
| void solver::add_not_distinct_axiom(app* e, enode* const* args) { | ||
| SASSERT(m.is_distinct(e)); | ||
| unsigned sz = e->get_num_args(); | ||
| if (sz <= 1) | ||
| return; | ||
|
|
||
| static const unsigned distinct_max_args = 24; | ||
| if (sz <= distinct_max_args) { | ||
| sat::literal_vector lits; | ||
| for (unsigned i = 0; i < sz; ++i) { | ||
| for (unsigned j = i + 1; j < sz; ++j) { | ||
| expr_ref eq(m.mk_eq(args[i]->get_owner(), args[j]->get_owner()), m); | ||
| sat::literal lit = internalize(eq, false, false, m_is_redundant); | ||
| lits.push_back(lit); | ||
| } | ||
| } | ||
| s().mk_clause(lits, false); | ||
| } | ||
| else { | ||
| // g(f(x_i)) = x_i | ||
| // f(x_1) = a + .... + f(x_n) = a >= 2 | ||
| sort* srt = m.get_sort(e->get_arg(0)); | ||
| SASSERT(!m.is_bool(srt)); | ||
| sort_ref u(m.mk_fresh_sort("distinct-elems"), m); | ||
| sort* u_ptr = u.get(); | ||
| func_decl_ref f(m.mk_fresh_func_decl("dist-f", "", 1, &srt, u), m); | ||
| func_decl_ref g(m.mk_fresh_func_decl("dist-g", "", 1, &u_ptr, srt), m); | ||
| expr_ref a(m.mk_fresh_const("a", u), m); | ||
| expr_ref_vector eqs(m); | ||
| for (expr* arg : *e) { | ||
| expr_ref fapp(m.mk_app(f, arg), m); | ||
| expr_ref gapp(m.mk_app(g, fapp.get()), m); | ||
| expr_ref eq(m.mk_eq(gapp, arg), m); | ||
| sat::literal lit = internalize(eq, false, false, m_is_redundant); | ||
| s().add_clause(1, &lit, false); | ||
| eqs.push_back(m.mk_eq(fapp, a)); | ||
| } | ||
| pb_util pb(m); | ||
| expr_ref at_least2(pb.mk_at_least_k(eqs.size(), eqs.c_ptr(), 2), m); | ||
| sat::literal lit = si.internalize(at_least2, m_is_redundant); | ||
| s().mk_clause(1, &lit, false); | ||
| } | ||
| } | ||
|
|
||
| void solver::add_distinct_axiom(app* e, enode* const* args) { | ||
| SASSERT(m.is_distinct(e)); | ||
| static const unsigned distinct_max_args = 24; | ||
| unsigned sz = e->get_num_args(); | ||
| if (sz <= 1) { | ||
| s().mk_clause(0, nullptr, m_is_redundant); | ||
| return; | ||
| } | ||
| if (sz <= distinct_max_args) { | ||
| for (unsigned i = 0; i < sz; ++i) { | ||
| for (unsigned j = i + 1; j < sz; ++j) { | ||
| expr_ref eq(m.mk_eq(args[i]->get_owner(), args[j]->get_owner()), m); | ||
| sat::literal lit = internalize(eq, true, false, m_is_redundant); | ||
| s().add_clause(1, &lit, m_is_redundant); | ||
| } | ||
| } | ||
| } | ||
| else { | ||
| // dist-f(x_1) = v_1 & ... & dist-f(x_n) = v_n | ||
| sort* srt = m.get_sort(e->get_arg(0)); | ||
| SASSERT(!m.is_bool(srt)); | ||
| sort_ref u(m.mk_fresh_sort("distinct-elems"), m); | ||
| func_decl_ref f(m.mk_fresh_func_decl("dist-f", "", 1, &srt, u), m); | ||
| for (unsigned i = 0; i < sz; ++i) { | ||
| expr_ref fapp(m.mk_app(f, e->get_arg(i)), m); | ||
| expr_ref fresh(m.mk_fresh_const("dist-value", u), m); | ||
| enode* n = m_egraph.mk(fresh, 0, nullptr); | ||
| n->mark_interpreted(); | ||
| expr_ref eq(m.mk_eq(fapp, fresh), m); | ||
| sat::literal lit = internalize(eq, false, false, m_is_redundant); | ||
| s().add_clause(1, &lit, m_is_redundant); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| void solver::axiomatize_basic(enode* n) { | ||
| expr* e = n->get_owner(); | ||
| if (m.is_ite(e)) { | ||
| app* a = to_app(e); | ||
| expr* c = a->get_arg(0); | ||
| expr* th = a->get_arg(1); | ||
| expr* el = a->get_arg(2); | ||
| sat::bool_var v = m_expr2var.to_bool_var(c); | ||
| SASSERT(v != sat::null_bool_var); | ||
| expr_ref eq_th(m.mk_eq(a, th), m); | ||
| expr_ref eq_el(m.mk_eq(a, el), m); | ||
| sat::literal lit_th = internalize(eq_th, false, false, m_is_redundant); | ||
| sat::literal lit_el = internalize(eq_el, false, false, m_is_redundant); | ||
| literal lits1[2] = { literal(v, true), lit_th }; | ||
| literal lits2[2] = { literal(v, false), lit_el }; | ||
| s().add_clause(2, lits1, m_is_redundant); | ||
| s().add_clause(2, lits2, m_is_redundant); | ||
| } | ||
| else if (m.is_distinct(e)) { | ||
| expr_ref_vector eqs(m); | ||
| unsigned sz = n->num_args(); | ||
| for (unsigned i = 0; i < sz; ++i) { | ||
| for (unsigned j = i + 1; j < sz; ++j) { | ||
| expr_ref eq(m.mk_eq(n->get_arg(i)->get_owner(), n->get_arg(j)->get_owner()), m); | ||
| eqs.push_back(eq); | ||
| } | ||
| } | ||
| expr_ref fml(m.mk_or(eqs), m); | ||
| sat::literal dist(m_expr2var.to_bool_var(e), false); | ||
| sat::literal some_eq = si.internalize(fml, m_is_redundant); | ||
| sat::literal lits1[2] = { ~dist, ~some_eq }; | ||
| sat::literal lits2[2] = { dist, some_eq }; | ||
| s().add_clause(2, lits1, m_is_redundant); | ||
| s().add_clause(2, lits2, m_is_redundant); | ||
| } | ||
| } | ||
|
|
||
| } |
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