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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2013-10-19 17:43:59 -07:00
parent 3996f58a8e
commit 3dd72f8f16
4 changed files with 54 additions and 42 deletions
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5
src/opt/opt_cmds.cpp
View file

@ -138,7 +138,10 @@ public:
virtual cmd_arg_kind next_arg_kind(cmd_context & ctx) const { return CPK_EXPR; }
virtual void set_next_arg(cmd_context & ctx, expr * t) {
m_opt_ctx().add_objective(t, m_is_max);
if (!is_app(t)) {
throw cmd_exception("malformed objective term: it cannot be a quantifier or bound variable");
}
m_opt_ctx().add_objective(to_app(t), m_is_max);
}
virtual void failure_cleanup(cmd_context & ctx) {

11
src/opt/opt_context.h
View file

@ -32,13 +32,12 @@ namespace opt {
class context {
ast_manager& m;
expr_ref_vector m_hard_constraints;
expr_ref_vector m_hard_constraints;
expr_ref_vector m_soft_constraints;
vector<rational> m_weights;
expr_ref_vector m_objectives;
svector<bool> m_is_max;
ref<solver> m_solver;
app_ref_vector m_objectives;
svector<bool> m_is_max;
ref<solver> m_solver;
public:
context(ast_manager& m):
@ -53,7 +52,7 @@ namespace opt {
m_weights.push_back(w);
}
void add_objective(expr* t, bool is_max) {
void add_objective(app* t, bool is_max) {
m_objectives.push_back(t);
m_is_max.push_back(is_max);
}

76
src/opt/optimize_objectives.cpp
View file

@ -29,58 +29,68 @@ namespace opt {
/*
Enumerate locally optimal assignments until fixedpoint.
*/
lbool mathsat_style_opt(opt_solver& s,
expr_ref_vector& objectives, svector<bool> const& is_max,
vector<inf_eps_rational<rational> >& values) {
enable_trace("maximize");
lbool mathsat_style_opt(
opt_solver& s,
app_ref_vector& objectives,
svector<bool> const& is_max,
vector<inf_eps_rational<rational> >& values)
{
SASSERT(is_max.size() == objectives.size());
enable_trace("maximize"); // NSB review: OK for now for debugging. Otherwise, use command-line /tr:maximize
// First check_sat call for initialize theories
lbool is_sat = s.check_sat(0, 0);
if (is_sat == l_false) {
return l_false;
if (is_sat != l_false) {
return is_sat;
}
s.push();
// Assume there is only one objective function
SASSERT(is_max.size() == 1);
ast_manager& m = objectives.get_manager();
arith_util autil(m);
app* objective = m.mk_fresh_const("objective", autil.mk_real());
if (is_max[0]) {
s.assert_expr(autil.mk_eq(objective, objectives[0].get()));
} else {
s.assert_expr(autil.mk_eq(objective, autil.mk_uminus(objectives[0].get())));
};
s.set_objective(objective);
bool ismax = is_max[0];
app_ref objective_var(m), objective_term(m), obj_eq(m);
objective_term = ismax?objectives[0].get():autil.mk_uminus(objectives[0].get());
sort* srt = m.get_sort(objective_term);
objective_var = m.mk_fresh_const("objective", srt);
obj_eq = autil.mk_eq(objective_var, objective_term);
s.assert_expr(obj_eq);
s.set_objective(objective_var); // NSB review: I would change signature of set_objective to take is_max and decide whether to add equation.
// Otherwise, the difference logic backends will not work.
s.toggle_objective(true);
is_sat = s.check_sat(0, 0);
while (is_sat != l_false) {
while (is_sat == l_true) {
// Extract values for objectives
inf_eps_rational<rational> val;
val = is_max[0] ? s.get_objective_value() : -s.get_objective_value();
val = is_max[0] ? s.get_objective_value() : -s.get_objective_value();
// Check whether objective is unbounded
if (!val.is_rational()) {
values.reset();
values.push_back(val);
break;
}
// If values have initial data, they will be dropped
// NSB: review: what if optimal is 1-epsilon. Then the check also fails.
values.reset();
values.push_back(val);
// 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(val.get_rational(), 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());
if (!val.is_rational()) {
break;
}
expr_ref constraint(m);
constraint = autil.mk_gt(objective_term, autil.mk_numeral(val.get_rational(), srt));
s.assert_expr(constraint);
is_sat = s.check_sat(0, 0);
}
s.pop(1);
if (is_sat == l_undef) {
return is_sat;
}
SASSERT(is_sat == l_false); // NSB review: not really water-tight with cancellation and with infinitesimal solutions.
return l_true;
}
@ -90,7 +100,7 @@ namespace opt {
*/
lbool optimize_objectives(opt_solver& s,
expr_ref_vector& objectives, svector<bool> const& is_max,
app_ref_vector& objectives, svector<bool> const& is_max,
vector<inf_eps_rational<rational> >& values) {
return mathsat_style_opt(s, objectives, is_max, values);
}

4
src/opt/optimize_objectives.h
View file

@ -28,8 +28,8 @@ namespace opt {
*/
lbool optimize_objectives(opt_solver& s,
expr_ref_vector& objectives, svector<bool> const& is_max,
vector<inf_eps_rational<rational> >& values);
app_ref_vector& objectives, svector<bool> const& is_max,
vector<inf_eps_rational<rational> >& values);
};
#endif