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https://github.com/Z3Prover/z3
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661 lines
24 KiB
C++
661 lines
24 KiB
C++
/*++
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Copyright (c) 2006 Microsoft Corporation
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Module Name:
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smt_consequences.cpp
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Abstract:
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Tuned consequence finding for smt_context.
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Author:
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nbjorner 2016-07-28.
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Revision History:
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--*/
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#include "util/max_cliques.h"
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#include "util/stopwatch.h"
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#include "ast/ast_util.h"
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#include "ast/ast_pp.h"
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#include "ast/datatype_decl_plugin.h"
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#include "model/model_pp.h"
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#include "smt/smt_context.h"
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namespace smt {
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expr_ref context::antecedent2fml(index_set const& vars) {
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expr_ref_vector premises(m_manager);
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index_set::iterator it = vars.begin(), end = vars.end();
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for (; it != end; ++it) {
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expr* e = bool_var2expr(*it);
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e = m_assumption2orig.find(e);
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premises.push_back(get_assignment(*it) != l_false ? e : m_manager.mk_not(e));
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}
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return mk_and(premises);
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}
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//
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// The literal lit is assigned at the search level, so it follows from the assumptions.
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// We retrieve the set of assumptions it depends on in the set 's'.
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// The map m_antecedents contains the association from these literals to the assumptions they depend on.
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// We then examine the contents of the literal lit and augment the set of consequences in one of the following cases:
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// - e is a propositional atom and it is one of the variables that is to be fixed.
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// - e is an equality between a variable and value that is to be fixed.
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// - e is a data-type recognizer of a variable that is to be fixed.
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//
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void context::extract_fixed_consequences(literal lit, index_set const& assumptions, expr_ref_vector& conseq) {
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ast_manager& m = m_manager;
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datatype_util dt(m);
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expr* e1, *e2;
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expr_ref fml(m);
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if (lit == true_literal) return;
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expr* e = bool_var2expr(lit.var());
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TRACE("context", display(tout << mk_pp(e, m) << "\n"););
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index_set s;
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if (assumptions.contains(lit.var())) {
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s.insert(lit.var());
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}
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else {
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justify(lit, s);
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}
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m_antecedents.insert(lit.var(), s);
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TRACE("context", display_literal_verbose(tout, lit);
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for (index_set::iterator it = s.begin(), end = s.end(); it != end; ++it) {
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tout << " " << *it;
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}
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tout << "\n";);
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bool found = false;
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if (m_var2val.contains(e)) {
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found = true;
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m_var2val.erase(e);
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e = m_var2orig.find(e);
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fml = lit.sign() ? m.mk_not(e) : e;
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}
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else if (!lit.sign() && m.is_eq(e, e1, e2)) {
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if (m_var2val.contains(e2) && m.is_value(e1)) {
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found = true;
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m_var2val.erase(e2);
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e2 = m_var2orig.find(e2);
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std::swap(e1, e2);
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fml = m.mk_eq(e1, e2);
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}
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else if (m_var2val.contains(e1) && m.is_value(e2)) {
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found = true;
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m_var2val.erase(e1);
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e1 = m_var2orig.find(e1);
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fml = m.mk_eq(e1, e2);
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}
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}
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else if (!lit.sign() && is_app(e) && dt.is_recognizer(to_app(e)->get_decl())) {
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if (m_var2val.contains(to_app(e)->get_arg(0))) {
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found = true;
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fml = m.mk_eq(to_app(e)->get_arg(0), m.mk_const(dt.get_recognizer_constructor(to_app(e)->get_decl())));
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m_var2val.erase(to_app(e)->get_arg(0));
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}
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}
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if (found) {
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fml = m.mk_implies(antecedent2fml(s), fml);
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conseq.push_back(fml);
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}
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}
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void context::justify(literal lit, index_set& s) {
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ast_manager& m = m_manager;
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(void)m;
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b_justification js = get_justification(lit.var());
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switch (js.get_kind()) {
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case b_justification::CLAUSE: {
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clause * cls = js.get_clause();
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if (!cls) break;
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unsigned num_lits = cls->get_num_literals();
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for (unsigned j = 0; j < num_lits; ++j) {
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literal lit2 = cls->get_literal(j);
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if (lit2.var() != lit.var()) {
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s |= m_antecedents.find(lit2.var());
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}
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}
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break;
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}
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case b_justification::BIN_CLAUSE: {
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s |= m_antecedents.find(js.get_literal().var());
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break;
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}
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case b_justification::AXIOM: {
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break;
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}
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case b_justification::JUSTIFICATION: {
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literal_vector literals;
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m_conflict_resolution->justification2literals(js.get_justification(), literals);
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for (unsigned j = 0; j < literals.size(); ++j) {
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if (!m_antecedents.contains(literals[j].var())) {
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TRACE("context", tout << literals[j] << " " << mk_pp(bool_var2expr(literals[j].var()), m) << "\n";);
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}
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s |= m_antecedents.find(literals[j].var());
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}
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break;
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}
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}
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}
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void context::extract_fixed_consequences(unsigned& start, index_set const& assumptions, expr_ref_vector& conseq) {
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pop_to_search_lvl();
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SASSERT(!inconsistent());
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literal_vector const& lits = assigned_literals();
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unsigned sz = lits.size();
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for (unsigned i = start; i < sz; ++i) {
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extract_fixed_consequences(lits[i], assumptions, conseq);
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}
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start = sz;
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SASSERT(!inconsistent());
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}
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//
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// The assignment stack is assumed consistent.
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// For each Boolean variable, we check if there is a literal assigned to the
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// opposite value of the reference model, and for non-Boolean variables we
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// check if the current state forces the variable to be distinct from the reference value.
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//
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// For yet to be determined Boolean variables we furthermore force the phase to be opposite
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// to the reference value in the attempt to let the sat engine emerge with a model that
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// rules out as many non-fixed variables as possible.
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//
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unsigned context::delete_unfixed(expr_ref_vector& unfixed) {
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ast_manager& m = m_manager;
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ptr_vector<expr> to_delete;
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obj_map<expr,expr*>::iterator it = m_var2val.begin(), end = m_var2val.end();
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for (; it != end; ++it) {
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expr* k = it->m_key;
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expr* v = it->m_value;
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if (m.is_bool(k)) {
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literal lit = get_literal(k);
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switch (get_assignment(lit)) {
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case l_true:
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if (m.is_false(v)) {
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to_delete.push_back(k);
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}
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else {
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force_phase(lit.var(), false);
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}
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break;
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case l_false:
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if (m.is_true(v)) {
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to_delete.push_back(k);
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}
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else {
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force_phase(lit.var(), true);
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}
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break;
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default:
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to_delete.push_back(k);
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break;
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}
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}
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else if (e_internalized(k) && m.are_distinct(v, get_enode(k)->get_root()->get_owner())) {
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to_delete.push_back(k);
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}
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else if (get_assignment(mk_diseq(k, v)) == l_true) {
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to_delete.push_back(k);
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}
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}
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for (unsigned i = 0; i < to_delete.size(); ++i) {
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m_var2val.remove(to_delete[i]);
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unfixed.push_back(to_delete[i]);
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}
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return to_delete.size();
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}
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#define are_equal(v, k) (e_internalized(k) && e_internalized(v) && get_enode(k)->get_root() == get_enode(v)->get_root())
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//
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// Extract equalities that are congruent at the search level.
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// Add a clause to short-circuit the congruence justifications for
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// next rounds.
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//
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unsigned context::extract_fixed_eqs(expr_ref_vector& conseq) {
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TRACE("context", tout << "extract fixed consequences\n";);
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ast_manager& m = m_manager;
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ptr_vector<expr> to_delete;
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expr_ref fml(m), eq(m);
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obj_map<expr,expr*>::iterator it = m_var2val.begin(), end = m_var2val.end();
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for (; it != end; ++it) {
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expr* k = it->m_key;
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expr* v = it->m_value;
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if (!m.is_bool(k) && are_equal(k, v)) {
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literal_vector literals;
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m_conflict_resolution->eq2literals(get_enode(v), get_enode(k), literals);
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index_set s;
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for (unsigned i = 0; i < literals.size(); ++i) {
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SASSERT(get_assign_level(literals[i]) <= get_search_level());
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s |= m_antecedents.find(literals[i].var());
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}
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fml = m.mk_eq(m_var2orig.find(k), v);
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fml = m.mk_implies(antecedent2fml(s), fml);
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conseq.push_back(fml);
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to_delete.push_back(k);
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for (unsigned i = 0; i < literals.size(); ++i) {
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literals[i].neg();
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}
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literal lit = mk_diseq(k, v);
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literals.push_back(lit);
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mk_clause(literals.size(), literals.c_ptr(), 0);
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TRACE("context", display_literals_verbose(tout, literals.size(), literals.c_ptr()););
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}
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}
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for (unsigned i = 0; i < to_delete.size(); ++i) {
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m_var2val.remove(to_delete[i]);
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}
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return to_delete.size();
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}
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literal context::mk_diseq(expr* e, expr* val) {
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ast_manager& m = m_manager;
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if (m.is_bool(e) && b_internalized(e)) {
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return literal(get_bool_var(e), m.is_true(val));
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}
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else if (m.is_bool(e)) {
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internalize_formula(e, false);
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return literal(get_bool_var(e), !m.is_true(val));
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}
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else {
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expr_ref eq(mk_eq_atom(e, val), m);
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internalize_formula(eq, false);
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return literal(get_bool_var(eq), true);
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}
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}
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lbool context::get_consequences(expr_ref_vector const& assumptions0,
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expr_ref_vector const& vars0,
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expr_ref_vector& conseq,
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expr_ref_vector& unfixed) {
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m_antecedents.reset();
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m_antecedents.insert(true_literal.var(), index_set());
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pop_to_base_lvl();
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ast_manager& m = m_manager;
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expr_ref_vector vars(m), assumptions(m);
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m_var2val.reset();
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m_var2orig.reset();
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m_assumption2orig.reset();
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bool pushed = false;
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for (unsigned i = 0; i < vars0.size(); ++i) {
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expr* v = vars0[i];
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if (is_uninterp_const(v)) {
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vars.push_back(v);
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m_var2orig.insert(v, v);
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}
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else {
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if (!pushed) {
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pushed = true;
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push();
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}
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expr_ref c(m.mk_fresh_const("v", m.get_sort(v)), m);
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expr_ref eq(m.mk_eq(c, v), m);
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assert_expr(eq);
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vars.push_back(c);
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m_var2orig.insert(c, v);
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}
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}
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for (unsigned i = 0; i < assumptions0.size(); ++i) {
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expr* a = assumptions0[i];
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if (is_uninterp_const(a)) {
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assumptions.push_back(a);
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m_assumption2orig.insert(a, a);
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}
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else {
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if (!pushed) {
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pushed = true;
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push();
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}
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expr_ref c(m.mk_fresh_const("a", m.get_sort(a)), m);
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expr_ref eq(m.mk_eq(c, a), m);
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assert_expr(eq);
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assumptions.push_back(c);
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m_assumption2orig.insert(c, a);
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}
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}
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lbool is_sat = check(assumptions.size(), assumptions.c_ptr());
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if (is_sat != l_true) {
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TRACE("context", tout << is_sat << "\n";);
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if (pushed) pop(1);
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return is_sat;
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}
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index_set _assumptions;
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for (unsigned i = 0; i < assumptions.size(); ++i) {
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_assumptions.insert(get_literal(assumptions[i].get()).var());
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}
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model_ref mdl;
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get_model(mdl);
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expr_ref_vector trail(m);
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model_evaluator eval(*mdl.get());
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expr_ref val(m);
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TRACE("context", model_pp(tout, *mdl););
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for (unsigned i = 0; i < vars.size(); ++i) {
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eval(vars[i].get(), val);
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if (m.is_value(val)) {
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trail.push_back(val);
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m_var2val.insert(vars[i].get(), val);
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}
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else {
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unfixed.push_back(vars[i].get());
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}
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}
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unsigned num_units = 0;
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extract_fixed_consequences(num_units, _assumptions, conseq);
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app_ref eq(m);
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TRACE("context",
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tout << "vars: " << vars.size() << "\n";
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tout << "lits: " << num_units << "\n";);
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m_case_split_queue->init_search_eh();
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unsigned num_iterations = 0;
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unsigned num_fixed_eqs = 0;
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unsigned chunk_size = 100;
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while (!m_var2val.empty()) {
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obj_map<expr,expr*>::iterator it = m_var2val.begin(), end = m_var2val.end();
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unsigned num_vars = 0;
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for (; it != end && num_vars < chunk_size; ++it) {
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if (get_cancel_flag()) {
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if (pushed) pop(1);
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return l_undef;
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}
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expr* e = it->m_key;
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expr* val = it->m_value;
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literal lit = mk_diseq(e, val);
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mark_as_relevant(lit);
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if (get_assignment(lit) != l_undef) {
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continue;
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}
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++num_vars;
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push_scope();
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assign(lit, b_justification::mk_axiom(), true);
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if (!propagate()) {
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if (!resolve_conflict() || inconsistent()) {
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TRACE("context", tout << "inconsistent\n";);
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SASSERT(inconsistent());
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m_conflict = null_b_justification;
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m_not_l = null_literal;
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SASSERT(m_search_lvl == get_search_level());
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}
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}
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}
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SASSERT(!inconsistent());
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++num_iterations;
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lbool is_sat = l_undef;
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while (true) {
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is_sat = bounded_search();
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if (is_sat != l_true && m_last_search_failure != OK) {
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if (pushed) pop(1);
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return is_sat;
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}
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if (is_sat == l_undef) {
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IF_VERBOSE(1, verbose_stream() << "(get-consequences inc-limits)\n";);
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inc_limits();
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continue;
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}
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break;
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}
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if (is_sat == l_false) {
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SASSERT(inconsistent());
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m_conflict = null_b_justification;
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m_not_l = null_literal;
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}
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if (is_sat == l_true) {
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delete_unfixed(unfixed);
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}
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extract_fixed_consequences(num_units, _assumptions, conseq);
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num_fixed_eqs += extract_fixed_eqs(conseq);
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IF_VERBOSE(1, display_consequence_progress(verbose_stream(), num_iterations, m_var2val.size(), conseq.size(),
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unfixed.size(), num_fixed_eqs););
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TRACE("context", display_consequence_progress(tout, num_iterations, m_var2val.size(), conseq.size(),
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unfixed.size(), num_fixed_eqs););
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}
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end_search();
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DEBUG_CODE(validate_consequences(assumptions, vars, conseq, unfixed););
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if (pushed) {
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pop(1);
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}
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return l_true;
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}
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void context::display_consequence_progress(std::ostream& out, unsigned it, unsigned nv, unsigned fixed, unsigned unfixed, unsigned eq) {
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out << "(get-consequences"
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<< " iterations: " << it
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<< " variables: " << nv
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<< " fixed: " << fixed
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<< " unfixed: " << unfixed
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<< " fixed-eqs: " << eq
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<< ")\n";
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}
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void context::extract_cores(expr_ref_vector const& asms, vector<expr_ref_vector>& cores, unsigned& min_core_size) {
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index_set _asms, _nasms;
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u_map<expr*> var2expr;
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for (unsigned i = 0; i < asms.size(); ++i) {
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literal lit = get_literal(asms[i]);
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_asms.insert(lit.index());
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_nasms.insert((~lit).index());
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var2expr.insert(lit.var(), asms[i]);
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}
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m_antecedents.reset();
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literal_vector const& lits = assigned_literals();
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for (unsigned i = 0; i < lits.size(); ++i) {
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literal lit = lits[i];
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index_set s;
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if (_asms.contains(lit.index())) {
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s.insert(lit.var());
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}
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else {
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justify(lit, s);
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}
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m_antecedents.insert(lit.var(), s);
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if (_nasms.contains(lit.index())) {
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expr_ref_vector core(m_manager);
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index_set::iterator it = s.begin(), end = s.end();
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for (; it != end; ++it) {
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core.push_back(var2expr[*it]);
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}
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core.push_back(var2expr[lit.var()]);
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cores.push_back(core);
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min_core_size = std::min(min_core_size, core.size());
|
|
}
|
|
}
|
|
}
|
|
|
|
void context::preferred_sat(literal_vector& lits) {
|
|
bool retry = true;
|
|
while (retry) {
|
|
retry = false;
|
|
for (unsigned i = 0; i < lits.size(); ++i) {
|
|
literal lit = lits[i];
|
|
if (lit == null_literal || get_assignment(lit) != l_undef) {
|
|
continue;
|
|
}
|
|
push_scope();
|
|
assign(lit, b_justification::mk_axiom(), true);
|
|
while (!propagate()) {
|
|
lits[i] = null_literal;
|
|
retry = true;
|
|
if (!resolve_conflict() || inconsistent()) {
|
|
SASSERT(inconsistent());
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void context::display_partial_assignment(std::ostream& out, expr_ref_vector const& asms, unsigned min_core_size) {
|
|
unsigned num_true = 0, num_false = 0, num_undef = 0;
|
|
for (unsigned i = 0; i < asms.size(); ++i) {
|
|
literal lit = get_literal(asms[i]);
|
|
if (get_assignment(lit) == l_false) {
|
|
++num_false;
|
|
}
|
|
if (get_assignment(lit) == l_true) {
|
|
++num_true;
|
|
}
|
|
if (get_assignment(lit) == l_undef) {
|
|
++num_undef;
|
|
}
|
|
}
|
|
out << "(smt.preferred-sat true: " << num_true << " false: " << num_false << " undef: " << num_undef << " min core: " << min_core_size << ")\n";
|
|
}
|
|
|
|
lbool context::preferred_sat(expr_ref_vector const& asms, vector<expr_ref_vector>& cores) {
|
|
pop_to_base_lvl();
|
|
cores.reset();
|
|
setup_context(false);
|
|
internalize_assertions();
|
|
if (m_asserted_formulas.inconsistent() || inconsistent()) {
|
|
return l_false;
|
|
}
|
|
scoped_mk_model smk(*this);
|
|
init_search();
|
|
flet<bool> l(m_searching, true);
|
|
unsigned level = m_scope_lvl;
|
|
unsigned min_core_size = UINT_MAX;
|
|
lbool is_sat = l_true;
|
|
unsigned num_restarts = 0;
|
|
|
|
while (true) {
|
|
if (m_manager.canceled()) {
|
|
is_sat = l_undef;
|
|
break;
|
|
}
|
|
literal_vector lits;
|
|
for (unsigned i = 0; i < asms.size(); ++i) {
|
|
lits.push_back(get_literal(asms[i]));
|
|
}
|
|
preferred_sat(lits);
|
|
if (inconsistent()) {
|
|
SASSERT(m_scope_lvl == level);
|
|
is_sat = l_false;
|
|
break;
|
|
}
|
|
extract_cores(asms, cores, min_core_size);
|
|
IF_VERBOSE(1, display_partial_assignment(verbose_stream(), asms, min_core_size););
|
|
|
|
if (min_core_size <= 10) {
|
|
is_sat = l_undef;
|
|
break;
|
|
}
|
|
|
|
is_sat = bounded_search();
|
|
if (!restart(is_sat, level)) {
|
|
break;
|
|
}
|
|
++num_restarts;
|
|
if (num_restarts >= min_core_size) {
|
|
is_sat = l_undef;
|
|
while (num_restarts <= 10*min_core_size) {
|
|
is_sat = bounded_search();
|
|
if (!restart(is_sat, level)) {
|
|
break;
|
|
}
|
|
++num_restarts;
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
end_search();
|
|
|
|
return check_finalize(is_sat);
|
|
}
|
|
|
|
struct neg_literal {
|
|
unsigned negate(unsigned i) {
|
|
return (~to_literal(i)).index();
|
|
}
|
|
};
|
|
|
|
lbool context::find_mutexes(expr_ref_vector const& vars, vector<expr_ref_vector>& mutexes) {
|
|
unsigned_vector ps;
|
|
max_cliques<neg_literal> mc;
|
|
expr_ref lit(m_manager);
|
|
for (unsigned i = 0; i < vars.size(); ++i) {
|
|
expr* n = vars[i];
|
|
bool neg = m_manager.is_not(n, n);
|
|
if (b_internalized(n)) {
|
|
ps.push_back(literal(get_bool_var(n), neg).index());
|
|
}
|
|
}
|
|
for (unsigned i = 0; i < m_watches.size(); ++i) {
|
|
watch_list & w = m_watches[i];
|
|
for (literal const* it = w.begin_literals(), *end = w.end_literals(); it != end; ++it) {
|
|
unsigned idx1 = (~to_literal(i)).index();
|
|
unsigned idx2 = it->index();
|
|
if (idx1 < idx2) {
|
|
mc.add_edge(idx1, idx2);
|
|
}
|
|
}
|
|
}
|
|
vector<unsigned_vector> _mutexes;
|
|
mc.cliques(ps, _mutexes);
|
|
for (unsigned i = 0; i < _mutexes.size(); ++i) {
|
|
expr_ref_vector lits(m_manager);
|
|
for (unsigned j = 0; j < _mutexes[i].size(); ++j) {
|
|
literal2expr(to_literal(_mutexes[i][j]), lit);
|
|
lits.push_back(lit);
|
|
}
|
|
mutexes.push_back(lits);
|
|
}
|
|
return l_true;
|
|
}
|
|
|
|
//
|
|
// Validate, in a slow pass, that the current consequences are correctly
|
|
// extracted.
|
|
//
|
|
void context::validate_consequences(expr_ref_vector const& assumptions, expr_ref_vector const& vars,
|
|
expr_ref_vector const& conseq, expr_ref_vector const& unfixed) {
|
|
ast_manager& m = m_manager;
|
|
expr_ref tmp(m);
|
|
SASSERT(!inconsistent());
|
|
for (unsigned i = 0; i < conseq.size(); ++i) {
|
|
push();
|
|
for (unsigned j = 0; j < assumptions.size(); ++j) {
|
|
assert_expr(assumptions[j]);
|
|
}
|
|
TRACE("context", tout << "checking: " << mk_pp(conseq[i], m) << "\n";);
|
|
tmp = m.mk_not(conseq[i]);
|
|
assert_expr(tmp);
|
|
VERIFY(check() != l_true);
|
|
pop(1);
|
|
}
|
|
model_ref mdl;
|
|
for (unsigned i = 0; i < unfixed.size(); ++i) {
|
|
push();
|
|
for (unsigned j = 0; j < assumptions.size(); ++j) {
|
|
assert_expr(assumptions[j]);
|
|
}
|
|
TRACE("context", tout << "checking unfixed: " << mk_pp(unfixed[i], m) << "\n";);
|
|
lbool is_sat = check();
|
|
SASSERT(is_sat != l_false);
|
|
if (is_sat == l_true) {
|
|
get_model(mdl);
|
|
mdl->eval(unfixed[i], tmp);
|
|
if (m.is_value(tmp)) {
|
|
tmp = m.mk_not(m.mk_eq(unfixed[i], tmp));
|
|
assert_expr(tmp);
|
|
is_sat = check();
|
|
SASSERT(is_sat != l_false);
|
|
}
|
|
}
|
|
pop(1);
|
|
}
|
|
}
|
|
|
|
}
|