z3-z3-4.13.0.src.qe.mbp.mbp_plugin.cpp Maven / Gradle / Ivy
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/*++
Copyright (c) 2015 Microsoft Corporation
Module Name:
mpb_plugin.cpp
Abstract:
Model-based projection plugin utilities
Author:
Nikolaj Bjorner (nbjorner) 2015-5-29
--*/
#include "ast/rewriter/expr_safe_replace.h"
#include "ast/ast_pp.h"
#include "ast/ast_util.h"
#include "ast/occurs.h"
#include "ast/rewriter/th_rewriter.h"
#include "ast/expr_functors.h"
#include "ast/for_each_expr.h"
#include "ast/scoped_proof.h"
#include "qe/mbp/mbp_plugin.h"
#include "model/model_pp.h"
#include "model/model_evaluator.h"
namespace mbp {
struct noop_op_proc {
void operator()(expr*) {}
};
void project_plugin::mark_rec(expr_mark& visited, expr* e) {
for_each_expr_proc fe;
for_each_expr(fe, visited, e);
}
void project_plugin::mark_rec(expr_mark& visited, expr_ref_vector const& es) {
for (expr* e : es)
mark_rec(visited, e);
}
/**
\brief return two terms that are equal in the model.
The distinct term t is false in model, so there
are at least two arguments of t that are equal in the model.
*/
expr_ref project_plugin::pick_equality(ast_manager& m, model& model, expr* t) {
SASSERT(m.is_distinct(t));
expr_ref val(m);
expr_ref_vector vals(m);
obj_map val2expr;
app* alit = to_app(t);
SASSERT(alit->get_num_args() > 1);
if (alit->get_num_args() == 2)
return expr_ref(m.mk_eq(alit->get_arg(0), alit->get_arg(1)), m);
for (expr* e1 : *alit) {
expr* e2;
val = model(e1);
TRACE("qe", tout << mk_pp(e1, m) << " |-> " << val << "\n";);
if (val2expr.find(val, e2)) {
return expr_ref(m.mk_eq(e1, e2), m);
}
val2expr.insert(val, e1);
vals.push_back(val);
}
for (unsigned i = 0; i < alit->get_num_args(); ++i) {
for (unsigned j = i + 1; j < alit->get_num_args(); ++j) {
expr* e1 = alit->get_arg(i);
expr* e2 = alit->get_arg(j);
val = m.mk_eq(e1, e2);
if (!model.is_false(val))
return expr_ref(m.mk_eq(e1, e2), m);
}
}
UNREACHABLE();
return expr_ref(nullptr, m);
}
void project_plugin::erase(expr_ref_vector& lits, unsigned& i) {
lits[i] = lits.back();
lits.pop_back();
--i;
}
void project_plugin::push_back(expr_ref_vector& lits, expr* e) {
if (!m.is_true(e))
lits.push_back(e);
}
bool project_plugin::reduce(model_evaluator& eval, model& model, expr* fml, expr_ref_vector& fmls) {
expr* nfml, * f1, * f2, * f3;
expr_ref val(m);
model.set_inline();
if (m.is_not(fml, nfml) && m.is_distinct(nfml))
push_back(fmls, pick_equality(m, model, nfml));
else if (m.is_or(fml)) {
for (expr* arg : *to_app(fml)) {
val = eval(arg);
if (m.is_true(val)) {
fmls.push_back(arg);
break;
}
}
}
else if (m.is_and(fml)) {
fmls.append(to_app(fml)->get_num_args(), to_app(fml)->get_args());
}
else if (m.is_iff(fml, f1, f2) || (m.is_not(fml, nfml) && m.is_xor(nfml, f1, f2))) {
val = eval(f1);
if (m.is_false(val)) {
push_back(fmls, mk_not(m, f1));
push_back(fmls, mk_not(m, f2));
}
else {
push_back(fmls, f1);
push_back(fmls, f2);
}
}
else if (m.is_implies(fml, f1, f2)) {
val = eval(f2);
if (m.is_true(val))
push_back(fmls, f2);
else
push_back(fmls, mk_not(m, f1));
}
else if (m.is_ite(fml, f1, f2, f3)) {
val = eval(f1);
if (m.is_true(val)) {
push_back(fmls, f1);
push_back(fmls, f2);
}
else {
push_back(fmls, mk_not(m, f1));
push_back(fmls, f3);
}
}
else if (m.is_not(fml, nfml) && m.is_not(nfml, nfml)) {
push_back(fmls, nfml);
}
else if (m.is_not(fml, nfml) && m.is_and(nfml)) {
for (expr* arg : *to_app(nfml)) {
val = eval(arg);
if (m.is_false(val)) {
push_back(fmls, mk_not(m, arg));
break;
}
}
}
else if (m.is_not(fml, nfml) && m.is_or(nfml)) {
for (expr* arg : *to_app(nfml))
push_back(fmls, mk_not(m, arg));
}
else if ((m.is_not(fml, nfml) && m.is_iff(nfml, f1, f2)) || m.is_xor(fml, f1, f2)) {
val = eval(f1);
if (m.is_true(val))
f2 = mk_not(m, f2);
else
f1 = mk_not(m, f1);
push_back(fmls, f1);
push_back(fmls, f2);
}
else if (m.is_not(fml, nfml) && m.is_implies(nfml, f1, f2)) {
push_back(fmls, f1);
push_back(fmls, mk_not(m, f2));
}
else if (m.is_not(fml, nfml) && m.is_ite(nfml, f1, f2, f3)) {
val = eval(f1);
if (m.is_true(val)) {
push_back(fmls, f1);
push_back(fmls, mk_not(m, f2));
}
else {
push_back(fmls, mk_not(m, f1));
push_back(fmls, mk_not(m, f3));
}
}
else
return false;
return true;
}
void project_plugin::extract_literals(model& model, app_ref_vector const& vars, expr_ref_vector& fmls) {
m_cache.reset();
m_bool_visited.reset();
expr_ref val(m);
model_evaluator eval(model);
eval.set_expand_array_equalities(true);
TRACE("qe", tout << fmls << "\n";);
DEBUG_CODE(for (expr* fml : fmls) { CTRACE("qe", m.is_false(eval(fml)), tout << mk_pp(fml, m) << " is false\n" << model;); SASSERT(!m.is_false(eval(fml))); });
for (unsigned i = 0; i < fmls.size(); ++i) {
expr* nfml, * fml = fmls.get(i);
if (reduce(eval, model, fml, fmls))
erase(fmls, i);
else if (m.is_not(fml, nfml))
extract_bools(eval, fmls, i, nfml, false);
else
extract_bools(eval, fmls, i, fml, true);
}
TRACE("qe", tout << fmls << "\n";);
}
void project_plugin::extract_bools(model_evaluator& eval, expr_ref_vector& fmls, unsigned idx, expr* fml, bool is_true) {
TRACE("qe", tout << "extract bools: " << mk_pp(fml, m) << "\n";);
if (!is_app(fml))
return;
m_to_visit.reset();
m_to_visit.append(to_app(fml)->get_num_args(), to_app(fml)->get_args());
while (!m_to_visit.empty()) {
if (!m.inc())
return;
expr* e = m_to_visit.back();
if (m_cache.get(e->get_id(), nullptr)) {
m_to_visit.pop_back();
}
else if (!is_app(e)) {
m_cache.setx(e->get_id(), e);
m_to_visit.pop_back();
}
else if (visit_ite(eval, e, fmls))
continue;
else if (visit_bool(eval, e, fmls))
continue;
else
visit_app(e);
}
SASSERT(m_to_visit.empty());
m_to_visit.push_back(fml);
visit_app(fml);
SASSERT(m_to_visit.empty());
expr* new_fml = m_cache.get(fml->get_id(), nullptr);
SASSERT(new_fml);
if (new_fml != fml)
fmls[idx] = is_true ? new_fml : mk_not(m, new_fml);
}
bool project_plugin::is_true(model_evaluator& eval, expr* e) {
expr_ref val = eval(e);
bool tt = m.is_true(val);
if (!tt && !m.is_false(val) && contains_uninterpreted(val)) {
IF_VERBOSE(1, verbose_stream() << "mbp failed on " << mk_pp(e, m) << " := " << val << "\n");
throw default_exception("could not evaluate Boolean in model");
}
SASSERT(tt || m.is_false(val));
return tt;
}
bool project_plugin::visit_ite(model_evaluator& eval, expr* e, expr_ref_vector& fmls) {
expr* c = nullptr, * th = nullptr, * el = nullptr;
if (m.is_ite(e, c, th, el)) {
bool tt = is_true(eval, c);
if (!m_bool_visited.is_marked(c))
fmls.push_back(tt ? c : mk_not(m, c));
m_bool_visited.mark(c);
expr* s = tt ? th : el;
expr* t = m_cache.get(s->get_id(), nullptr);
if (t) {
m_to_visit.pop_back();
m_cache.setx(e->get_id(), t);
}
else
m_to_visit.push_back(s);
return true;
}
else
return false;
}
bool project_plugin::visit_bool(model_evaluator& eval, expr* e, expr_ref_vector& fmls) {
if (m.is_bool(e) && !m.is_true(e) && !m.is_false(e)) {
bool tt = is_true(eval, e);
if (!m_bool_visited.is_marked(e))
fmls.push_back(tt ? e : mk_not(m, e));
m_bool_visited.mark(e);
m_cache.setx(e->get_id(), m.mk_bool_val(tt));
m_to_visit.pop_back();
return true;
}
else
return false;
}
void project_plugin::visit_app(expr* e) {
unsigned sz = m_to_visit.size();
m_args.reset();
bool diff = false;
for (expr* arg : *to_app(e)) {
expr* new_arg = m_cache.get(arg->get_id(), nullptr);
diff |= new_arg != arg;
if (new_arg == nullptr)
m_to_visit.push_back(arg);
else
m_args.push_back(new_arg);
}
if (sz == m_to_visit.size()) {
m_cache.setx(e->get_id(), diff ? m.mk_app(to_app(e)->get_decl(), m_args) : e);
m_to_visit.pop_back();
}
}
void project_plugin::mark_non_ground(expr* e) {
m_to_visit.push_back(e);
while (!m_to_visit.empty()) {
expr* e = m_to_visit.back();
if (!is_app(e)) {
m_visited.mark(e);
m_to_visit.pop_back();
continue;
}
unsigned n = m_to_visit.size();
for (expr* arg : *to_app(e)) {
if (!m_visited.is_marked(arg))
m_to_visit.push_back(arg);
else if (m_non_ground.is_marked(arg))
m_non_ground.mark(e);
}
if (m_to_visit.size() == n) {
m_visited.mark(e);
m_to_visit.pop_back();
}
}
}
}