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A rudimentary version of MathSAT optimization

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Remarks:
(1) The core procedure accepts maximization only
(2) Add lazy initialization to min_maximize_cmd
(3) The procedure isn't working with composite objective yet.
This commit is contained in:
Anh-Dung Phan 2013-10-18 18:00:24 -07:00
parent 898609a3ef
commit a44044fb15
8 changed files with 114 additions and 33 deletions
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51
src/opt/optimize_objectives.cpp
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@ -22,6 +22,7 @@ Notes:
#include "optimize_objectives.h"
#include "opt_solver.h"
#include "arith_decl_plugin.h"
namespace opt {
@ -31,23 +32,47 @@ namespace opt {
lbool mathsat_style_opt(opt_solver& s,
expr_ref_vector& objectives, svector<bool> const& is_max,
vector<optional<rational> >& values) {
lbool is_sat;
is_sat = s.check_sat(0,0);
if (is_sat != l_true) {
return is_sat;
enable_trace("maximize");
// First check_sat call for initialize theories
lbool is_sat = s.check_sat(0, 0);
if (is_sat == l_false) {
return l_false;
}
// assume that s is instrumented to produce locally optimal assignments.
// Assume there is only one objective function
ast_manager& m = objectives.get_manager();
arith_util autil(m);
app* objective = is_max[0] ? (app*) objectives[0].get() : autil.mk_uminus(objectives[0].get());
s.set_objective(objective);
s.toggle_objective(true);
is_sat = s.check_sat(0, 0);
while (is_sat != l_false) {
model_ref model;
s.get_model(model);
// extract values for objectives.
// store them in values.
// assert there must be something better.
is_sat = s.check_sat(0,0);
}
return l_true;
// Extract values for objectives.
optional<rational> rat;
rat = s.get_objective_value();
// Unbounded objective
if (!rat) {
values.reset();
values.push_back(rat);
return l_true;
}
// If values have initial data, they will be dropped.
values.reset();
values.push_back(rat);
// Assert there must be something better.
expr_ref_vector assumptions(m);
expr* bound = m.mk_fresh_const("bound", m.mk_bool_sort());
assumptions.push_back(bound);
expr* r = autil.mk_numeral(*rat, false);
s.assert_expr(m.mk_eq(bound, is_max[0] ? autil.mk_gt(objectives[0].get(), r) : autil.mk_lt(objectives[0].get(), r)));
is_sat = s.check_sat(1, assumptions.c_ptr());
}
return l_true;
}
/**