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walk/gsat

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-03-03 16:10:18 -08:00
parent 1e32f1fbb5
commit d819784500
3 changed files with 189 additions and 21 deletions
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2
CMakeLists.txt
View file

@ -34,7 +34,7 @@ project(Z3 C CXX)
set(Z3_VERSION_MAJOR 4)
set(Z3_VERSION_MINOR 5)
set(Z3_VERSION_PATCH 1)
set(Z3_VERSION_TWEAK 0)
set(Z3_VERSION_TWEAK 0303)
set(Z3_FULL_VERSION 0)
set(Z3_VERSION "${Z3_VERSION_MAJOR}.${Z3_VERSION_MINOR}.${Z3_VERSION_PATCH}.${Z3_VERSION_TWEAK}")
message(STATUS "Z3 version ${Z3_VERSION}")

177
src/sat/sat_local_search.cpp
View file

@ -187,6 +187,13 @@ namespace sat {
}
}
void local_search::verify_unsat_stack() const {
for (unsigned i = 0; i < m_unsat_stack.size(); ++i) {
constraint const& c = m_constraints[m_unsat_stack[i]];
SASSERT(c.m_k < constraint_value(c));
}
}
unsigned local_search::constraint_value(constraint const& c) const {
unsigned value = 0;
for (unsigned i = 0; i < c.size(); ++i) {
@ -226,7 +233,6 @@ namespace sat {
local_search::local_search(solver& s) :
m_par(0) {
std::cout << "Parameter1: " << s.m_config.m_local_search_parameter1 << "\n";
m_vars.reserve(s.num_vars());
// copy units
@ -322,15 +328,28 @@ namespace sat {
lbool local_search::check() {
return check(0, 0);
}
lbool local_search::check(unsigned sz, literal const* assumptions, parallel* p) {
flet<parallel*> _p(m_par, p);
m_model.reset();
unsigned num_constraints = m_constraints.size();
for (unsigned i = 0; i < sz; ++i) {
add_clause(1, assumptions + i);
void local_search::walksat() {
reinit();
timer timer;
timer.start();
unsigned step = 0, total_steps = 0, max_steps = (1 << 20);
for (unsigned tries = 1; !m_unsat_stack.empty() && m_limit.inc(); ++tries) {
for (step = 0; step < max_steps && !m_unsat_stack.empty(); ++step) {
pick_flip_walksat();
}
total_steps += step;
if (tries % 10 == 0) {
IF_VERBOSE(1, verbose_stream() << "(sat-local-search"
<< " :tries " << tries
<< " :steps " << total_steps
<< " :unsat " << m_unsat_stack.size()
<< " :time " << timer.get_seconds() << ")\n";);
}
}
init();
}
void local_search::gsat() {
reinit();
bool reach_known_best_value = false;
bool_var flipvar;
@ -347,8 +366,8 @@ namespace sat {
break;
}
}
flipvar = pick_var();
flip(flipvar);
flipvar = pick_var_gsat();
flip_gsat(flipvar);
m_vars[flipvar].m_time_stamp = step;
}
IF_VERBOSE(1, if (tries % 10 == 0)
@ -363,6 +382,26 @@ namespace sat {
m_par->get_phase(*this);
}
}
}
lbool local_search::check(unsigned sz, literal const* assumptions, parallel* p) {
flet<parallel*> _p(m_par, p);
m_model.reset();
unsigned num_constraints = m_constraints.size();
for (unsigned i = 0; i < sz; ++i) {
add_clause(1, assumptions + i);
}
init();
switch (m_config.mode()) {
case local_search_mode::gsat:
gsat();
break;
case local_search_mode::wsat:
walksat();
break;
}
// remove unit clauses from assumptions.
m_constraints.shrink(num_constraints);
@ -398,7 +437,111 @@ namespace sat {
m_unsat_stack.push_back(c);
}
void local_search::flip(bool_var flipvar)
void local_search::pick_flip_walksat() {
m_good_vars.reset();
bool_var v;
constraint const& c = m_constraints[m_unsat_stack[m_rand() % m_unsat_stack.size()]];
SASSERT(c.m_k < constraint_value(c));
if (m_rand() % 100 < 5) {
// display(std::cout, c);
unsigned best_bsb = 0;
// find the first one, to fast break the rest
unsigned i = 0;
while (true) {
v = c[i].var();
if (is_true(c[i])) {
bool tt = cur_solution(v);
int_vector const& falsep = m_vars[v].m_watch[!tt];
for (unsigned j = 0; j < falsep.size(); ++j) {
unsigned ci = falsep[j];
if (constraint_slack(ci) < 0)
++best_bsb;
else if (constraint_slack(ci) == 0)
// >= unsat_stack_fill_pointer is enough
best_bsb += m_constraints.size();
}
break;
}
++i;
}
m_good_vars.push_back(v);
for (++i; i < c.size(); ++i) {
v = c[i].var();
if (is_true(c[i])) {
bool found = false;
unsigned bsb = 0;
bool tt = cur_solution(v);
int_vector const& falsep = m_vars[v].m_watch[!tt];
for (unsigned j = 0; j < falsep.size() && !found; ++j) {
unsigned ci = falsep[j];
if (constraint_slack(ci) < 0) {
if (bsb == best_bsb) {
found = true;
}
else {
++bsb;
}
}
else if (constraint_slack(ci) == 0) {
// >= unsat_stack_fill_pointer is enough
bsb += m_constraints.size();
if (bsb > best_bsb) {
found = true;
}
}
}
if (!found) {
if (bsb < best_bsb) {
best_bsb = bsb;
m_good_vars.reset();
m_good_vars.push_back(v);
}
else {// if (bb == best_bb)
m_good_vars.push_back(v);
}
}
}
}
}
else {
for (unsigned i = 0; i < c.size(); ++i) {
if (is_true(c[i]))
m_good_vars.push_back(c[i].var());
}
}
SASSERT(!m_good_vars.empty());
//std::cout << m_good_vars.size() << "\n";
flip_walksat(m_good_vars[m_rand() % m_good_vars.size()]);
}
void local_search::flip_walksat(bool_var flipvar) {
m_vars[flipvar].m_value = !cur_solution(flipvar);
bool flip_is_true = cur_solution(flipvar);
int_vector& truep = m_vars[flipvar].m_watch[flip_is_true];
int_vector& falsep = m_vars[flipvar].m_watch[!flip_is_true];
for (unsigned i = 0; i < truep.size(); ++i) {
unsigned ci = truep[i];
constraint& c = m_constraints[ci];
--c.m_slack;
if (c.m_slack == -1) { // from 0 to -1: sat -> unsat
unsat(ci);
}
}
for (unsigned i = 0; i < falsep.size(); ++i) {
unsigned ci = falsep[i];
constraint& c = m_constraints[ci];
++c.m_slack;
if (c.m_slack == 0) { // from -1 to 0: unsat -> sat
sat(ci);
}
}
// verify_unsat_stack();
}
void local_search::flip_gsat(bool_var flipvar)
{
// already changed truth value!!!!
m_vars[flipvar].m_value = !cur_solution(flipvar);
@ -558,7 +701,7 @@ namespace sat {
(time_stamp(v) < time_stamp(best_var))))))));
}
bool_var local_search::pick_var() {
bool_var local_search::pick_var_gsat() {
bool_var best_var = m_vars.size()-1; // sentinel variable
// SAT Mode
if (m_unsat_stack.empty()) {
@ -613,7 +756,6 @@ namespace sat {
TRACE("sat",
tout << "seed:\t" << m_config.seed() << '\n';
tout << "cutoff time:\t" << m_config.cutoff_time() << '\n';
tout << "strategy id:\t" << m_config.strategy_id() << '\n';
tout << "best_known_value:\t" << m_config.best_known_value() << '\n';
tout << "max_steps:\t" << max_steps << '\n';
@ -622,7 +764,12 @@ namespace sat {
void local_search::print_info(std::ostream& out) {
for (unsigned v = 0; v < num_vars(); ++v) {
out << "v" << v << "\t" << m_vars[v].m_neighbors.size() << '\t' << cur_solution(v) << '\t' << conf_change(v) << '\t' << score(v) << '\t' << slack_score(v) << '\n';
out << "v" << v << "\t"
<< m_vars[v].m_neighbors.size() << '\t'
<< cur_solution(v) << '\t'
<< conf_change(v) << '\t'
<< score(v) << '\t'
<< slack_score(v) << '\n';
}
}

31
src/sat/sat_local_search.h
View file

@ -27,25 +27,33 @@ namespace sat {
class parallel;
enum local_search_mode {
gsat,
wsat
};
class local_search_config {
unsigned m_seed;
unsigned m_strategy_id;
int m_best_known_value;
local_search_mode m_mode;
public:
local_search_config()
{
local_search_config() {
m_seed = 0;
m_strategy_id = 0;
m_best_known_value = INT_MAX;
m_mode = local_search_mode::wsat;
}
unsigned seed() const { return m_seed; }
unsigned strategy_id() const { return m_strategy_id; }
unsigned best_known_value() const { return m_best_known_value; }
local_search_mode mode() const { return m_mode; }
void set_seed(unsigned s) { m_seed = s; }
void set_strategy_id(unsigned i) { m_strategy_id = i; }
void set_best_known_value(unsigned v) { m_best_known_value = v; }
void set_mode(local_search_mode m) { m_mode = m; }
};
@ -131,7 +139,8 @@ namespace sat {
unsigned num_constraints() const { return m_constraints.size(); } // constraint index from 1 to num_constraint
unsigned constraint_slack(unsigned ci) const { return m_constraints[ci].m_slack; }
// int_vector nb_slack; // constraint_k - ob_var(same in ob) - none_ob_true_terms_count. if < 0: some ob var might be flipped to false, result in an ob decreasing
// bool_vector has_true_ob_terms;
@ -142,6 +151,8 @@ namespace sat {
// configuration changed decreasing variables (score>0 and conf_change==true)
int_vector goodvar_stack;
svector<bool_var> m_good_vars; // candidate variables to flip on.
// information about solution
int objective_value; // the objective function value corresponds to the current solution
bool_vector best_solution; // !var: the best solution so far
@ -167,9 +178,17 @@ namespace sat {
void init_scores();
void init_goodvars();
bool_var pick_var();
bool_var pick_var_gsat();
void flip(bool_var v);
void flip_gsat(bool_var v);
void pick_flip_walksat();
void flip_walksat(bool_var v);
void walksat();
void gsat();
void unsat(unsigned c);
@ -187,6 +206,8 @@ namespace sat {
void verify_solution() const;
void verify_unsat_stack() const;
void verify_constraint(constraint const& c) const;
unsigned constraint_value(constraint const& c) const;