z3-z3-4.13.0.src.sat.sat_prob.cpp Maven / Gradle / Ivy
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/*++
Copyright (c) 2019 Microsoft Corporation
Module Name:
sat_prob.cpp
Abstract:
PROB Local search module for clauses
Author:
Nikolaj Bjorner 2019-4-23
Notes:
--*/
#include "sat/sat_prob.h"
#include "sat/sat_solver.h"
#include "util/luby.h"
namespace sat {
prob::~prob() {
for (clause* cp : m_clause_db) {
m_alloc.del_clause(cp);
}
}
lbool prob::check(unsigned n, literal const* assumptions, parallel* p) {
VERIFY(n == 0);
init();
while (m_limit.inc() && m_best_min_unsat > 0) {
if (should_restart()) do_restart();
else flip();
}
if (m_best_min_unsat == 0) {
return l_true;
}
return l_undef;
}
void prob::flip() {
bool_var v = pick_var();
flip(v);
if (m_unsat.size() < m_best_min_unsat) {
save_best_values();
}
}
bool_var prob::pick_var() {
unsigned cls_idx = m_unsat.elem_at(m_rand() % m_unsat.size());
double sum_prob = 0;
unsigned i = 0;
clause const& c = get_clause(cls_idx);
for (literal lit : c) {
double prob = m_prob_break[m_breaks[lit.var()]];
m_probs[i++] = prob;
sum_prob += prob;
}
double lim = sum_prob * ((double)m_rand() / m_rand.max_value());
do {
lim -= m_probs[--i];
}
while (lim >= 0 && i > 0);
return c[i].var();
}
void prob::flip(bool_var v) {
++m_flips;
literal lit = literal(v, !m_values[v]);
literal nlit = ~lit;
SASSERT(is_true(lit));
SASSERT(lit.index() < m_use_list.size());
SASSERT(m_use_list_index.size() == m_use_list.size() + 1);
for (unsigned cls_idx : use_list(*this, lit)) {
clause_info& ci = m_clauses[cls_idx];
ci.del(lit);
switch (ci.m_num_trues) {
case 0:
m_unsat.insert_fresh(cls_idx);
dec_break(lit);
break;
case 1:
inc_break(to_literal(ci.m_trues));
break;
default:
break;
}
}
for (unsigned cls_idx : use_list(*this, nlit)) {
clause_info& ci = m_clauses[cls_idx];
switch (ci.m_num_trues) {
case 0:
m_unsat.remove(cls_idx);
inc_break(nlit);
break;
case 1:
dec_break(to_literal(ci.m_trues));
break;
default:
break;
}
ci.add(nlit);
}
m_values[v] = !m_values[v];
}
void prob::add(unsigned n, literal const* c) {
clause* cls = m_alloc.mk_clause(n, c, false);
unsigned idx = m_clause_db.size();
m_clause_db.push_back(cls);
m_clauses.push_back(clause_info());
for (literal lit : *cls) {
m_values.reserve(lit.var()+1);
m_breaks.reserve(lit.var()+1);
m_use_list.reserve((1+lit.var())*2);
m_use_list[lit.index()].push_back(idx);
}
m_probs.reserve(n+1);
}
void prob::add(solver const& s) {
m_values.reserve(s.num_vars(), false);
unsigned trail_sz = s.init_trail_size();
for (unsigned i = 0; i < trail_sz; ++i) {
add(1, s.m_trail.data() + i);
}
unsigned sz = s.m_watches.size();
for (unsigned l_idx = 0; l_idx < sz; ++l_idx) {
literal l1 = ~to_literal(l_idx);
watch_list const & wlist = s.m_watches[l_idx];
for (watched const& w : wlist) {
if (!w.is_binary_non_learned_clause())
continue;
literal l2 = w.get_literal();
if (l1.index() > l2.index())
continue;
literal ls[2] = { l1, l2 };
add(2, ls);
}
}
for (clause* c : s.m_clauses) {
add(c->size(), c->begin());
}
}
void prob::save_best_values() {
m_best_min_unsat = m_unsat.size();
m_best_values.reserve(m_values.size());
m_model.reserve(m_values.size());
for (unsigned i = 0; i < m_values.size(); ++i) {
m_best_values[i] = m_values[i];
m_model[i] = to_lbool(m_values[i]);
}
}
void prob::flatten_use_list() {
m_use_list_index.reset();
m_flat_use_list.reset();
for (auto const& ul : m_use_list) {
m_use_list_index.push_back(m_flat_use_list.size());
m_flat_use_list.append(ul);
}
m_use_list_index.push_back(m_flat_use_list.size());
}
void prob::init_clauses() {
for (unsigned& b : m_breaks) {
b = 0;
}
m_unsat.reset();
for (unsigned i = 0; i < m_clauses.size(); ++i) {
clause_info& ci = m_clauses[i];
ci.m_num_trues = 0;
ci.m_trues = 0;
clause const& c = get_clause(i);
for (literal lit : c) {
if (is_true(lit)) {
ci.add(lit);
}
}
switch (ci.m_num_trues) {
case 0:
m_unsat.insert_fresh(i);
break;
case 1:
inc_break(to_literal(ci.m_trues));
break;
default:
break;
}
}
}
void prob::auto_config() {
unsigned max_len = 0;
for (clause* cp : m_clause_db) {
max_len = std::max(max_len, cp->size());
}
// ProbSat magic constants
switch (max_len) {
case 0: case 1: case 2: case 3: m_config.m_cb = 2.5; break;
case 4: m_config.m_cb = 2.85; break;
case 5: m_config.m_cb = 3.7; break;
case 6: m_config.m_cb = 5.1; break;
default: m_config.m_cb = 5.4; break;
}
unsigned max_num_occ = 0;
for (auto const& ul : m_use_list) {
max_num_occ = std::max(max_num_occ, ul.size());
}
// vodoo from prob-sat
m_prob_break.reserve(max_num_occ+1);
for (int i = 0; i <= static_cast(max_num_occ); ++i) {
m_prob_break[i] = pow(m_config.m_cb, -i);
}
}
void prob::log() {
double sec = m_stopwatch.get_current_seconds();
double kflips_per_sec = m_flips / (1000.0 * sec);
IF_VERBOSE(0, verbose_stream()
<< sec << " sec. "
<< (m_flips/1000) << " kflips "
<< m_best_min_unsat << " unsat "
<< kflips_per_sec << " kflips/sec "
<< m_restart_count << " restarts\n");
}
void prob::init() {
flatten_use_list();
init_random_values();
init_clauses();
auto_config();
save_best_values();
m_restart_count = 1;
m_flips = 0;
m_next_restart = m_config.m_restart_offset;
m_stopwatch.start();
}
void prob::init_random_values() {
for (unsigned v = 0; v < m_values.size(); ++v) {
m_values[v] = (m_rand() % 2 == 0);
}
}
void prob::init_best_values() {
for (unsigned v = 0; v < m_values.size(); ++v) {
m_values[v] = m_best_values[v];
}
}
void prob::init_near_best_values() {
for (unsigned v = 0; v < m_values.size(); ++v) {
if (m_rand(100) < m_config.m_prob_random_init) {
m_values[v] = !m_best_values[v];
}
else {
m_values[v] = m_best_values[v];
}
}
}
void prob::do_restart() {
reinit_values();
init_clauses();
m_next_restart += m_config.m_restart_offset*get_luby(m_restart_count++);
log();
}
bool prob::should_restart() {
return m_flips >= m_next_restart;
}
void prob::reinit_values() {
init_near_best_values();
}
std::ostream& prob::display(std::ostream& out) const {
unsigned num_cls = m_clauses.size();
for (unsigned i = 0; i < num_cls; ++i) {
out << get_clause(i) << " ";
auto const& ci = m_clauses[i];
out << ci.m_num_trues << "\n";
}
return out;
}
void prob::invariant() {
}
}