mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-06-06 14:13:23 +00:00
Code Activity

working on upper bound optimziation

Browse source 
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2013-11-03 14:54:42 -08:00
parent e5698119d7
commit c0de1e34ac
17 changed files with 343 additions and 125 deletions
Download patch file Download diff file Expand all files Collapse all files

153
src/opt/optimize_objectives.cpp
View file

@ -62,26 +62,18 @@ namespace opt {
}
}
/*
Enumerate locally optimal assignments until fixedpoint.
*/
lbool optimize_objectives::basic_opt(app_ref_vector& objectives) {
arith_util autil(m);
opt_solver::scoped_push _push(*s);
for (unsigned i = 0; i < objectives.size(); ++i) {
m_vars.push_back(s->add_objective(objectives[i].get()));
}
lbool optimize_objectives::basic_opt() {
opt_solver::toggle_objective _t(*s, true);
lbool is_sat = l_true;
// Disabled while testing and tuning:
// is_sat = update_upper();
opt_solver::toggle_objective _t(*s, true);
while (is_sat == l_true && !m_cancel) {
is_sat = update_lower();
is_sat = s->check_sat(0, 0);
if (is_sat == l_true) {
update_lower();
}
}
if (m_cancel || is_sat == l_undef) {
@ -90,73 +82,117 @@ namespace opt {
return l_true;
}
lbool optimize_objectives::update_lower() {
lbool is_sat = s->check_sat(0, 0);
if (is_sat == l_true) {
model_ref md;
s->get_model(md);
set_max(m_lower, s->get_objective_values());
IF_VERBOSE(1,
for (unsigned i = 0; i < m_lower.size(); ++i) {
verbose_stream() << m_lower[i] << " ";
}
verbose_stream() << "\n";
// model_pp(verbose_stream(), *md);
);
expr_ref_vector disj(m);
expr_ref constraint(m);
for (unsigned i = 0; i < m_lower.size(); ++i) {
inf_eps const& v = m_lower[i];
disj.push_back(s->block_lower_bound(i, v));
}
constraint = m.mk_or(disj.size(), disj.c_ptr());
s->assert_expr(constraint);
/*
Enumerate locally optimal assignments until fixedpoint.
*/
lbool optimize_objectives::farkas_opt() {
smt::theory_opt& opt = s->get_optimizer();
IF_VERBOSE(1, verbose_stream() << typeid(opt).name() << "\n";);
if (typeid(smt::theory_inf_arith) != typeid(opt)) {
return l_undef;
}
return is_sat;
opt_solver::toggle_objective _t(*s, true);
lbool is_sat= l_true;
while (is_sat == l_true && !m_cancel) {
is_sat = update_upper();
}
if (m_cancel || is_sat == l_undef) {
return l_undef;
}
return l_true;
}
void optimize_objectives::update_lower() {
model_ref md;
s->get_model(md);
set_max(m_lower, s->get_objective_values());
IF_VERBOSE(1,
for (unsigned i = 0; i < m_lower.size(); ++i) {
verbose_stream() << m_lower[i] << " ";
}
verbose_stream() << "\n";
// model_pp(verbose_stream(), *md);
);
expr_ref_vector disj(m);
expr_ref constraint(m);
for (unsigned i = 0; i < m_lower.size(); ++i) {
inf_eps const& v = m_lower[i];
disj.push_back(s->block_lower_bound(i, v));
}
constraint = m.mk_or(disj.size(), disj.c_ptr());
s->assert_expr(constraint);
}
lbool optimize_objectives::update_upper() {
smt::theory_opt& opt = s->get_optimizer();
IF_VERBOSE(1, verbose_stream() << typeid(opt).name() << "\n";);
if (typeid(smt::theory_inf_arith) != typeid(opt)) {
return l_true;
}
SASSERT(typeid(smt::theory_inf_arith) == typeid(opt));
smt::theory_inf_arith& th = dynamic_cast<smt::theory_inf_arith&>(opt);
expr_ref bound(m);
expr_ref_vector bounds(m);
opt_solver::scoped_push _push(*s);
//
// NB: we have to create all bound expressions before calling check_sat
// because the state after check_sat is not at base level.
//
vector<inf_eps> mid;
for (unsigned i = 0; i < m_lower.size() && !m_cancel; ++i) {
if (m_lower[i] < m_upper[i]) {
SASSERT(m_upper[i].get_infinity().is_pos());
smt::theory_var v = m_vars[i];
bound = th.block_upper_bound(v, m_upper[i]);
mid.push_back((m_upper[i]+m_lower[i])/rational(2));
bound = th.block_upper_bound(v, mid[i]);
bounds.push_back(bound);
}
else {
bounds.push_back(0);
mid.push_back(inf_eps());
}
}
bool progress = false;
for (unsigned i = 0; i < m_lower.size() && !m_cancel; ++i) {
if (m_lower[i] < m_upper[i]) {
if (m_lower[i] <= mid[i] && mid[i] <= m_upper[i] && m_lower[i] < m_upper[i]) {
th.enable_record_conflict(bounds[i].get());
lbool is_sat = s->check_sat(1, bounds.c_ptr() + i);
if (is_sat == l_true) {
th.enable_record_conflict(0);
switch(is_sat) {
case l_true:
IF_VERBOSE(2, verbose_stream() << "Setting lower bound for v" << m_vars[i] << " to " << m_upper[i] << "\n";);
m_lower[i] = m_upper[i];
}
else if (is_sat == l_false) {
// else: TBD extract Farkas coefficients.
m_lower[i] = mid[i];
update_lower();
break;
case l_false:
if (!th.conflict_minimize().get_infinity().is_zero()) {
// bounds is not in the core. The context is unsat.
m_upper[i] = m_lower[i];
return l_false;
}
else {
m_upper[i] = std::min(m_upper[i], th.conflict_minimize());
}
break;
default:
return l_undef;
}
progress = true;
}
}
if (m_cancel) {
return l_undef;
}
if (!progress) {
return l_false;
}
return l_true;
}
@ -177,7 +213,24 @@ namespace opt {
// First check_sat call to initialize theories
lbool is_sat = s->check_sat(0, 0);
if (is_sat == l_true) {
is_sat = basic_opt(objectives);
opt_solver::scoped_push _push(*s);
for (unsigned i = 0; i < objectives.size(); ++i) {
m_vars.push_back(s->add_objective(objectives[i].get()));
}
if (m_engine == symbol("basic")) {
is_sat = basic_opt();
}
else if (m_engine == symbol("farkas")) {
is_sat = farkas_opt();
}
else {
// TODO: implement symba engine
// report error on bad configuration.
NOT_IMPLEMENTED_YET();
UNREACHABLE();
}
values.reset();
values.append(m_lower);
}