mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-04-13 20:38:43 +00:00
Code Activity

use lookahead for simplification

Browse source 
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-04-18 16:58:56 -07:00
parent 352f8b6cb9
commit a3f4d58b00
11 changed files with 183 additions and 45 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
src/sat/sat_config.cpp
View file

@ -37,6 +37,7 @@ namespace sat {
m_psm_glue("psm_glue") {
m_num_threads = 1;
m_local_search = 0;
m_lookahead_search = false;
updt_params(p);
}
@ -81,7 +82,8 @@ namespace sat {
m_max_conflicts = p.max_conflicts();
m_num_threads = p.threads();
m_local_search = p.local_search();
m_lookahead_search = p.lookahead_search();
// These parameters are not exposed
m_simplify_mult1 = _p.get_uint("simplify_mult1", 300);
m_simplify_mult2 = _p.get_double("simplify_mult2", 1.5);

1
src/sat/sat_config.h
View file

@ -59,6 +59,7 @@ namespace sat {
unsigned m_max_conflicts;
unsigned m_num_threads;
unsigned m_local_search;
bool m_lookahead_search;
unsigned m_simplify_mult1;
double m_simplify_mult2;

42
src/sat/sat_local_search.cpp
View file

@ -71,9 +71,8 @@ namespace sat {
void local_search::init_cur_solution() {
for (unsigned v = 0; v < num_vars(); ++v) {
// use bias with a small probability
if (m_rand() % 100 < 3) {
//m_vars[v].m_value = ((unsigned)(m_rand() % 100) < m_vars[v].m_bias);
m_vars[v].m_value = (50 < m_vars[v].m_bias);
if (m_rand() % 100 < 2) {
m_vars[v].m_value = ((unsigned)(m_rand() % 100) < m_vars[v].m_bias);
}
}
}
@ -138,20 +137,24 @@ namespace sat {
}
void local_search::reinit() {
// the following methods does NOT converge for pseudo-boolean
// can try other way to define "worse" and "better"
// the current best noise is below 1000
#if 0
if (m_best_unsat_rate > m_last_best_unsat_rate) {
// worse
m_noise -= m_noise * 2 * m_noise_delta;
m_best_unsat_rate *= 1000.0;
if (!m_is_pb) {
//
// the following methods does NOT converge for pseudo-boolean
// can try other way to define "worse" and "better"
// the current best noise is below 1000
//
if (m_best_unsat_rate > m_last_best_unsat_rate) {
// worse
m_noise -= m_noise * 2 * m_noise_delta;
m_best_unsat_rate *= 1000.0;
}
else {
// better
m_noise += (10000 - m_noise) * m_noise_delta;
}
}
else {
// better
m_noise += (10000 - m_noise) * m_noise_delta;
}
#endif
for (unsigned i = 0; i < m_constraints.size(); ++i) {
constraint& c = m_constraints[i];
c.m_slack = c.m_k;
@ -264,7 +267,7 @@ namespace sat {
unsigned id = m_constraints.size();
m_constraints.push_back(constraint(k));
for (unsigned i = 0; i < sz; ++i) {
m_vars.reserve(c[i].var() + 1);
m_vars.reserve(c[i].var() + 1);
literal t(~c[i]);
m_vars[t.var()].m_watch[is_pos(t)].push_back(pbcoeff(id, coeffs[i]));
m_constraints.back().push(t); // add coefficient to constraint?
@ -279,6 +282,7 @@ namespace sat {
}
void local_search::import(solver& s, bool _init) {
m_is_pb = false;
m_vars.reset();
m_constraints.reset();
@ -349,6 +353,7 @@ namespace sat {
// = ~c.lit() or (~c.lits() <= n - k)
// = k*c.lit() + ~c.lits() <= n
//
m_is_pb = true;
lits.reset();
coeffs.reset();
for (unsigned j = 0; j < n; ++j) lits.push_back(c[j]), coeffs.push_back(1);
@ -616,8 +621,7 @@ namespace sat {
// verify_unsat_stack();
}
void local_search::flip_gsat(bool_var flipvar)
{
void local_search::flip_gsat(bool_var flipvar) {
// already changed truth value!!!!
m_vars[flipvar].m_value = !cur_solution(flipvar);

1
src/sat/sat_local_search.h
View file

@ -144,6 +144,7 @@ namespace sat {
literal_vector m_assumptions;
unsigned m_num_non_binary_clauses;
bool m_is_pb;
inline bool is_pos(literal t) const { return !t.sign(); }
inline bool is_true(bool_var v) const { return cur_solution(v); }

135
src/sat/sat_lookahead.h
View file

@ -20,6 +20,8 @@ Notes:
#ifndef _SAT_LOOKAHEAD_H_
#define _SAT_LOOKAHEAD_H_
#include "sat_elim_eqs.h"
namespace sat {
struct pp_prefix {
@ -34,6 +36,9 @@ namespace sat {
for (unsigned i = 0; i <= d; ++i) {
if (0 != (p.m_prefix & (1ull << i))) out << "1"; else out << "0";
}
if (d < p.m_depth) {
out << " d:" << p.m_depth;
}
return out;
}
@ -309,6 +314,7 @@ namespace sat {
assign(u);
return false;
}
IF_VERBOSE(3, verbose_stream() << "tc1: " << u << " " << w << "\n";);
add_binary(u, w);
}
}
@ -367,7 +373,8 @@ namespace sat {
bool select(unsigned level) {
init_pre_selection(level);
unsigned max_num_cand = level == 0 ? m_freevars.size() : m_config.m_level_cand / level;
unsigned level_cand = std::max(m_config.m_level_cand, m_freevars.size() / 50);
unsigned max_num_cand = level == 0 ? m_freevars.size() : level_cand / level;
max_num_cand = std::max(m_config.m_min_cutoff, max_num_cand);
float sum = 0;
@ -1010,7 +1017,8 @@ namespace sat {
m_lits.push_back(lit_info());
m_rating.push_back(0);
m_vprefix.push_back(prefix());
m_freevars.insert(v);
if (!s.was_eliminated(v))
m_freevars.insert(v);
}
void init() {
@ -1040,11 +1048,31 @@ namespace sat {
}
}
copy_clauses(s.m_clauses);
copy_clauses(s.m_learned);
// copy units
unsigned trail_sz = s.init_trail_size();
for (unsigned i = 0; i < trail_sz; ++i) {
literal l = s.m_trail[i];
if (!s.was_eliminated(l.var()))
{
if (s.m_config.m_drat) m_drat.add(l, false);
assign(l);
}
}
propagate();
m_qhead = m_trail.size();
TRACE("sat", s.display(tout); display(tout););
}
void copy_clauses(clause_vector const& clauses) {
// copy clauses
clause_vector::const_iterator it = s.m_clauses.begin();
clause_vector::const_iterator end = s.m_clauses.end();
for (; it != end; ++it) {
clause_vector::const_iterator it = clauses.begin();
clause_vector::const_iterator end = clauses.end();
for (; it != end; ++it) {
clause& c = *(*it);
if (c.was_removed()) continue;
clause* c1 = m_cls_allocator.mk_clause(c.size(), c.begin(), false);
m_clauses.push_back(c1);
attach_clause(*c1);
@ -1053,17 +1081,6 @@ namespace sat {
}
if (s.m_config.m_drat) m_drat.add(c, false);
}
// copy units
unsigned trail_sz = s.init_trail_size();
for (unsigned i = 0; i < trail_sz; ++i) {
literal l = s.m_trail[i];
if (s.m_config.m_drat) m_drat.add(l, false);
assign(l);
}
propagate();
m_qhead = m_trail.size();
TRACE("sat", s.display(tout); display(tout););
}
// ------------------------------------
@ -1393,19 +1410,24 @@ namespace sat {
TRACE("sat", display_lookahead(tout); );
unsigned base = 2;
bool change = true;
bool first = true;
while (change && !inconsistent()) {
change = false;
for (unsigned i = 0; !inconsistent() && i < m_lookahead.size(); ++i) {
s.checkpoint();
literal lit = m_lookahead[i].m_lit;
if (is_fixed_at(lit, c_fixed_truth)) continue;
unsigned level = base + m_lookahead[i].m_offset;
if (m_stamp[lit.var()] >= level) {
continue;
}
if (scope_lvl() == 1) {
IF_VERBOSE(3, verbose_stream() << scope_lvl() << " " << lit << " binary: " << m_binary_trail.size() << " trail: " << m_trail_lim.back() << "\n";);
}
TRACE("sat", tout << "lookahead: " << lit << " @ " << m_lookahead[i].m_offset << "\n";);
reset_wnb(lit);
push_lookahead1(lit, level);
do_double(lit, base);
if (!first) do_double(lit, base);
bool unsat = inconsistent();
pop_lookahead1(lit);
if (unsat) {
@ -1424,7 +1446,13 @@ namespace sat {
if (c_fixed_truth - 2 * m_lookahead.size() < base) {
break;
}
base += 2 * m_lookahead.size();
if (first && !change) {
first = false;
change = true;
}
reset_wnb();
init_wnb();
// base += 2 * m_lookahead.size();
}
reset_wnb();
TRACE("sat", display_lookahead(tout); );
@ -1487,6 +1515,7 @@ namespace sat {
}
bool check_autarky(literal l, unsigned level) {
return false;
// no propagations are allowed to reduce clauses.
clause_vector::const_iterator it = m_full_watches[l.index()].begin();
clause_vector::const_iterator end = m_full_watches[l.index()].end();
@ -1568,7 +1597,7 @@ namespace sat {
}
void do_double(literal l, unsigned& base) {
if (!inconsistent() && scope_lvl() > 0 && dl_enabled(l)) {
if (!inconsistent() && scope_lvl() > 1 && dl_enabled(l)) {
if (get_wnb(l) > m_delta_trigger) {
if (dl_no_overflow(base)) {
++m_stats.m_double_lookahead_rounds;
@ -1588,6 +1617,7 @@ namespace sat {
SASSERT(dl_no_overflow(base));
unsigned dl_truth = base + 2 * m_lookahead.size() * (m_config.m_dl_max_iterations + 1);
scoped_level _sl(*this, dl_truth);
IF_VERBOSE(2, verbose_stream() << "double: " << l << "\n";);
init_wnb();
assign(l);
propagate();
@ -1769,9 +1799,6 @@ namespace sat {
m_drat(s),
m_level(2),
m_prefix(0) {
m_search_mode = lookahead_mode::searching;
scoped_level _sl(*this, c_fixed_truth);
init();
}
~lookahead() {
@ -1779,9 +1806,73 @@ namespace sat {
}
lbool check() {
{
m_search_mode = lookahead_mode::searching;
scoped_level _sl(*this, c_fixed_truth);
init();
}
return search();
}
void simplify() {
SASSERT(m_prefix == 0);
SASSERT(m_watches.empty());
m_search_mode = lookahead_mode::searching;
scoped_level _sl(*this, c_fixed_truth);
init();
if (inconsistent()) return;
inc_istamp();
literal l = choose();
if (inconsistent()) return;
SASSERT(m_trail_lim.empty());
unsigned num_units = 0;
for (unsigned i = 0; i < m_trail.size(); ++i) {
literal lit = m_trail[i];
if (s.value(lit) == l_undef && !s.was_eliminated(lit.var())) {
s.m_simplifier.propagate_unit(lit);
++num_units;
}
}
IF_VERBOSE(1, verbose_stream() << "units found: " << num_units << "\n";);
s.m_simplifier.subsume();
m_lookahead.reset();
}
void scc() {
SASSERT(m_prefix == 0);
SASSERT(m_watches.empty());
m_search_mode = lookahead_mode::searching;
scoped_level _sl(*this, c_fixed_truth);
init();
if (inconsistent()) return;
inc_istamp();
m_lookahead.reset();
if (select(0)) {
// extract equivalences
get_scc();
if (inconsistent()) return;
literal_vector roots;
bool_var_vector to_elim;
for (unsigned i = 0; i < s.num_vars(); ++i) {
roots.push_back(literal(i, false));
}
for (unsigned i = 0; i < m_candidates.size(); ++i) {
bool_var v = m_candidates[i].m_var;
literal lit = literal(v, false);
literal p = get_parent(lit);
if (p != null_literal && p.var() != v && !s.is_external(v) && !s.was_eliminated(v) && !s.was_eliminated(p.var())) {
to_elim.push_back(v);
roots[v] = p;
}
}
IF_VERBOSE(1, verbose_stream() << "eliminate " << to_elim.size() << " variables\n";);
elim_eqs elim(s);
elim(roots, to_elim);
}
m_lookahead.reset();
}
std::ostream& display(std::ostream& out) const {
out << "Prefix: " << pp_prefix(m_prefix, m_trail_lim.size()) << "\n";
out << "Level: " << m_level << "\n";

1
src/sat/sat_params.pyg
View file

@ -29,4 +29,5 @@ def_module_params('sat',
('cardinality.solver', BOOL, False, 'use cardinality solver'),
('xor.solver', BOOL, False, 'use xor solver'),
('local_search', UINT, 0, 'number of local search threads to find satisfiable solution'),
('lookahead_search', BOOL, False, 'use lookahead solver')
))

4
src/sat/sat_scc.cpp
View file

@ -76,7 +76,9 @@ namespace sat {
lowlink.resize(num_lits, UINT_MAX);
in_s.resize(num_lits, false);
literal_vector roots;
roots.resize(m_solver.num_vars(), null_literal);
for (unsigned i = 0; i < m_solver.num_vars(); ++i) {
roots.push_back(literal(i, false));
}
unsigned next_index = 0;
svector<frame> frames;
bool_var_vector to_elim;

8
src/sat/sat_simplifier.cpp
View file

@ -21,6 +21,7 @@ Revision History:
#include"sat_simplifier.h"
#include"sat_simplifier_params.hpp"
#include"sat_solver.h"
#include"sat_lookahead.h"
#include"stopwatch.h"
#include"trace.h"
@ -204,6 +205,11 @@ namespace sat {
}
while (!m_sub_todo.empty());
if (!learned) {
// perform lookahead simplification
lookahead(s).simplify();
}
bool vars_eliminated = m_num_elim_vars > old_num_elim_vars;
if (m_need_cleanup) {
@ -219,9 +225,11 @@ namespace sat {
cleanup_clauses(s.m_learned, true, true, learned_in_use_lists);
}
}
CASSERT("sat_solver", s.check_invariant());
TRACE("after_simplifier", s.display(tout); tout << "model_converter:\n"; s.m_mc.display(tout););
finalize();
}
/**

6
src/sat/sat_simplifier.h
View file

@ -130,13 +130,11 @@ namespace sat {
bool cleanup_clause(clause & c, bool in_use_list);
bool cleanup_clause(literal_vector & c);
void propagate_unit(literal l);
void elim_lit(clause & c, literal l);
void elim_dup_bins();
bool subsume_with_binaries();
void mark_as_not_learned_core(watch_list & wlist, literal l2);
void mark_as_not_learned(literal l1, literal l2);
void subsume();
void cleanup_watches();
void cleanup_clauses(clause_vector & cs, bool learned, bool vars_eliminated, bool in_use_lists);
@ -191,6 +189,10 @@ namespace sat {
void collect_statistics(statistics & st) const;
void reset_statistics();
void propagate_unit(literal l);
void subsume();
};
};

23
src/sat/sat_solver.cpp
View file

@ -22,6 +22,7 @@ Revision History:
#include"trace.h"
#include"max_cliques.h"
#include"scoped_ptr_vector.h"
#include"sat_lookahead.h"
// define to update glue during propagation
#define UPDATE_GLUE
@ -783,6 +784,9 @@ namespace sat {
pop_to_base_level();
IF_VERBOSE(2, verbose_stream() << "(sat.sat-solver)\n";);
SASSERT(at_base_lvl());
if (m_config.m_lookahead_search && num_lits == 0) {
return lookahead_search();
}
if ((m_config.m_num_threads > 1 || m_config.m_local_search > 0) && !m_par) {
return check_par(num_lits, lits);
}
@ -855,6 +859,20 @@ namespace sat {
ERROR_EX
};
lbool solver::lookahead_search() {
lookahead lh(*this);
lbool r = l_undef;
try {
r = lh.check();
m_model = lh.get_model();
}
catch (z3_exception&) {
lh.collect_statistics(m_lookahead_stats);
throw;
}
lh.collect_statistics(m_lookahead_stats);
return r;
}
lbool solver::check_par(unsigned num_lits, literal const* lits) {
scoped_ptr_vector<local_search> ls;
@ -1295,6 +1313,8 @@ namespace sat {
CASSERT("sat_simplify_bug", check_invariant());
}
lookahead(*this).scc();
sort_watch_lits();
CASSERT("sat_simplify_bug", check_invariant());
@ -2762,6 +2782,7 @@ namespace sat {
m_asymm_branch.collect_statistics(st);
m_probing.collect_statistics(st);
if (m_ext) m_ext->collect_statistics(st);
st.copy(m_lookahead_stats);
}
void solver::reset_statistics() {
@ -2770,6 +2791,7 @@ namespace sat {
m_simplifier.reset_statistics();
m_asymm_branch.reset_statistics();
m_probing.reset_statistics();
m_lookahead_stats.reset();
}
// -----------------------
@ -3605,6 +3627,7 @@ namespace sat {
if (m_solver.m_num_frozen > 0)
out << " :frozen " << m_solver.m_num_frozen;
}
out << " :units " << m_solver.init_trail_size();
out << " :gc-clause " << m_solver.m_stats.m_gc_clause;
out << mem_stat();
}

3
src/sat/sat_solver.h
View file

@ -141,6 +141,8 @@ namespace sat {
unsigned m_par_num_vars;
bool m_par_syncing_clauses;
statistics m_lookahead_stats;
void del_clauses(clause * const * begin, clause * const * end);
friend class integrity_checker;
@ -346,6 +348,7 @@ namespace sat {
void sort_watch_lits();
void exchange_par();
lbool check_par(unsigned num_lits, literal const* lits);
lbool lookahead_search();
// -----------------------
//