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maxres revised to handle weighted constraints

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2014-07-22 15:42:08 +02:00
parent bf35a62da7
commit 5e9bf2ef53
5 changed files with 177 additions and 83 deletions
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186
src/opt/maxres.cpp
View file

@ -12,62 +12,79 @@
using namespace opt;
struct maxres::imp {
ast_manager& m;
solver& s;
expr_ref_vector m_B;
expr_ref_vector m_D;
expr_ref_vector m_asms;
app_ref_vector m_clss;
model_ref m_model;
expr_ref_vector m_soft_constraints;
volatile bool m_cancel;
rational m_lower;
rational m_upper;
obj_map<expr, app*> m_asm2cls;
struct info {
app* m_cls;
rational m_weight;
info(app* cls, rational const& w):
m_cls(cls), m_weight(w) {}
info(): m_cls(0) {}
};
ast_manager& m;
solver& s;
expr_ref_vector m_B;
expr_ref_vector m_D;
expr_ref_vector m_asms;
model_ref m_model;
expr_ref_vector m_soft_constraints;
volatile bool m_cancel;
rational m_lower;
rational m_upper;
obj_map<expr, info> m_asm2info;
ptr_vector<expr> m_new_core;
mus m_mus;
expr_ref_vector m_trail;
imp(ast_manager& m, solver& s, expr_ref_vector& soft_constraints):
m(m), s(s), m_B(m), m_D(m), m_asms(m), m_clss(m), m_soft_constraints(soft_constraints),
m_cancel(false)
imp(ast_manager& m, solver& s, expr_ref_vector& soft_constraints, vector<rational> const& weights):
m(m), s(s), m_B(m), m_D(m), m_asms(m), m_soft_constraints(m),
m_cancel(false),
m_mus(s, m),
m_trail(m)
{
// TBD: this introduces an assertion to solver.
init_soft(weights, soft_constraints);
}
bool is_literal(expr* l) {
return
is_uninterp_const(l) ||
m.is_not(l, l) && is_uninterp_const(l);
(m.is_not(l, l) && is_uninterp_const(l));
}
void add_soft(expr* e) {
void add_soft(expr* e, rational const& w) {
TRACE("opt", tout << mk_pp(e, m) << "\n";);
expr_ref asum(m), fml(m);
app_ref cls(m);
cls = mk_cls(e);
m_clss.push_back(cls);
m_trail.push_back(cls);
if (is_literal(e)) {
m_asms.push_back(e);
asum = e;
}
else {
asum = m.mk_fresh_const("soft", m.mk_bool_sort());
fml = m.mk_iff(asum, e);
s.assert_expr(fml);
m_asms.push_back(asum);
}
m_asm2cls.insert(m_asms.back(), cls.get());
new_assumption(asum, cls, w);
m_upper += w;
}
void new_assumption(expr* e, app* cls, rational const& w) {
info inf(cls, w);
m_asm2info.insert(e, inf);
m_asms.push_back(e);
m_trail.push_back(e);
}
lbool operator()() {
expr_ref fml(m);
ptr_vector<expr> core, new_core;
ptr_vector<expr> core;
solver::scoped_push _sc(s);
for (unsigned i = 0; i < m_soft_constraints.size(); ++i) {
add_soft(m_soft_constraints[i].get());
}
m_upper = rational(m_soft_constraints.size());
while (true) {
TRACE("opt",
display_vec(tout, m_asms.size(), m_asms.c_ptr());
s.display(tout);
tout << "\n";
display(tout);
);
lbool is_sat = s.check_sat(m_asms.size(), m_asms.c_ptr());
if (m_cancel) {
@ -85,37 +102,21 @@ struct maxres::imp {
s.get_unsat_core(core);
TRACE("opt", display_vec(tout << "core: ", core.size(), core.c_ptr()););
SASSERT(!core.empty());
is_sat = minimize_core(core);
SASSERT(!core.empty());
if (core.empty()) {
return l_false;
}
#if 1
// minimize core:
mus ms(s, m);
for (unsigned i = 0; i < core.size(); ++i) {
app* cls = 0;
VERIFY(m_asm2cls.find(core[i], cls));
SASSERT(cls);
SASSERT(m.is_or(cls));
ms.add_soft(core[i], cls->get_num_args(), cls->get_args());
}
unsigned_vector mus_idx;
is_sat = ms.get_mus(mus_idx);
if (is_sat != l_true) {
return is_sat;
}
new_core.reset();
for (unsigned i = 0; i < mus_idx.size(); ++i) {
new_core.push_back(core[mus_idx[i]]);
}
core.reset();
core.append(new_core);
#endif
remove_core(core);
rational w = split_core(core);
TRACE("opt", display_vec(tout << "minimized core: ", core.size(), core.c_ptr()););
max_resolve(core);
max_resolve(core, w);
fml = m.mk_not(m.mk_and(m_B.size(), m_B.c_ptr()));
s.assert_expr(fml);
m_lower += rational::one();
m_lower += w;
break;
}
IF_VERBOSE(1, verbose_stream() << "(opt.max_res lower: " << m_lower << ")\n";);
@ -123,6 +124,57 @@ struct maxres::imp {
return l_true;
}
lbool minimize_core(ptr_vector<expr>& core) {
m_mus.reset();
for (unsigned i = 0; i < core.size(); ++i) {
app* cls = get_clause(core[i]);
SASSERT(cls);
SASSERT(m.is_or(cls));
m_mus.add_soft(core[i], cls->get_num_args(), cls->get_args());
}
unsigned_vector mus_idx;
lbool is_sat = m_mus.get_mus(mus_idx);
if (is_sat != l_true) {
return is_sat;
}
m_new_core.reset();
for (unsigned i = 0; i < mus_idx.size(); ++i) {
m_new_core.push_back(core[mus_idx[i]]);
}
core.reset();
core.append(m_new_core);
return l_true;
}
rational get_weight(expr* e) {
return m_asm2info.find(e).m_weight;
}
app* get_clause(expr* e) {
return m_asm2info.find(e).m_cls;
}
rational split_core(ptr_vector<expr> const& core) {
// find the minimal weight:
SASSERT(!core.empty());
rational w = get_weight(core[0]);
for (unsigned i = 1; i < core.size(); ++i) {
rational w2 = get_weight(core[i]);
if (w2 < w) {
w = w2;
}
}
// add fresh soft clauses for weights that are above w.
for (unsigned i = 0; i < core.size(); ++i) {
rational w2 = get_weight(core[i]);
if (w2 > w) {
new_assumption(core[i], get_clause(core[i]), w2 - w);
}
}
return w;
}
void display_vec(std::ostream& out, unsigned sz, expr* const* args) {
for (unsigned i = 0; i < sz; ++i) {
out << mk_pp(args[i], m) << " ";
@ -130,7 +182,14 @@ struct maxres::imp {
out << "\n";
}
void max_resolve(ptr_vector<expr>& core) {
void display(std::ostream& out) {
for (unsigned i = 0; i < m_asms.size(); ++i) {
expr* a = m_asms[i].get();
out << mk_pp(a, m) << " : " << get_weight(a) << "\n";
}
}
void max_resolve(ptr_vector<expr>& core, rational const& w) {
SASSERT(!core.empty());
expr_ref fml(m), asum(m);
app_ref cls(m);
@ -144,7 +203,6 @@ struct maxres::imp {
// d_i := (!core_{i+1} or d_{i+1}) for i = 0...sz-2
// soft (!d_i or core_i)
//
remove_core(core);
for (unsigned i = core.size()-1; i > 0; ) {
--i;
expr* d_i1 = m_D[i+1].get();
@ -155,11 +213,10 @@ struct maxres::imp {
asum = m.mk_fresh_const("a", m.mk_bool_sort());
cls = m.mk_implies(d_i, b_i);
fml = m.mk_iff(asum, cls);
s.assert_expr(fml);
m_asms.push_back(asum);
cls = mk_cls(cls);
m_clss.push_back(cls);
m_asm2cls.insert(asum, cls);
m_trail.push_back(cls);
new_assumption(asum, cls, w);
s.assert_expr(fml);
}
}
@ -199,9 +256,7 @@ struct maxres::imp {
for (unsigned i = 0; i < m_asms.size(); ++i) {
if (core.contains(m_asms[i].get())) {
m_asms[i] = m_asms.back();
m_clss[i] = m_clss.back();
m_asms.pop_back();
m_clss.pop_back();
--i;
}
}
@ -217,11 +272,12 @@ struct maxres::imp {
bool get_assignment(unsigned index) const {
expr_ref tmp(m);
m_model->eval(m_soft_constraints[index], tmp);
VERIFY(m_model->eval(m_soft_constraints[index], tmp));
return m.is_true(tmp);
}
void set_cancel(bool f) {
m_cancel = f;
m_mus.set_cancel(f);
}
void collect_statistics(statistics& st) const {
}
@ -232,10 +288,22 @@ struct maxres::imp {
;
}
void init_soft(vector<rational> const& weights, expr_ref_vector const& soft) {
m_soft_constraints.reset();
m_upper.reset();
m_lower.reset();
m_asm2info.reset();
m_trail.reset();
m_soft_constraints.append(soft);
for (unsigned i = 0; i < m_soft_constraints.size(); ++i) {
add_soft(m_soft_constraints[i].get(), weights[i]);
}
}
};
maxres::maxres(ast_manager& m, solver& s, expr_ref_vector& soft_constraints) {
m_imp = alloc(imp, m, s, soft_constraints);
maxres::maxres(ast_manager& m, solver& s, expr_ref_vector& soft_constraints, vector<rational> const& weights) {
m_imp = alloc(imp, m, s, soft_constraints, weights);
}
maxres::~maxres() {

2
src/opt/maxres.h
View file

@ -4,7 +4,7 @@ namespace opt {
struct imp;
imp* m_imp;
public:
maxres(ast_manager& m, solver& s, expr_ref_vector& soft_constraints);
maxres(ast_manager& m, solver& s, expr_ref_vector& soft_constraints, vector<rational>const& weights);
~maxres();
virtual lbool operator()();
virtual rational get_lower() const;

8
src/opt/maxsmt.cpp
View file

@ -39,16 +39,16 @@ namespace opt {
m_msolver = 0;
is_sat = m_s->check_sat(0, 0);
}
else if (m_maxsat_engine == symbol("maxres")) {
m_msolver = alloc(maxres, m, *m_s, m_soft_constraints, m_weights);
}
else if (is_maxsat_problem(m_weights)) {
if (m_maxsat_engine == symbol("core_maxsat")) {
m_msolver = alloc(core_maxsat, m, *m_s, m_soft_constraints);
}
else if (m_maxsat_engine == symbol("weighted_maxsat")) {
m_msolver = alloc(wmaxsmt, m, m_s.get(), m_soft_constraints, m_weights);
}
else if (m_maxsat_engine == symbol("maxres")) {
m_msolver = alloc(maxres, m, *m_s, m_soft_constraints);
}
}
else {
m_msolver = alloc(fu_malik, m, *m_s, m_soft_constraints);
}

60
src/opt/mus.cpp
View file

@ -16,9 +16,21 @@ struct mus::imp {
vector<smt::literal_vector> m_cls2lits;
expr_ref_vector m_vars;
obj_map<expr, unsigned> m_var2idx;
volatile bool m_cancel;
public:
imp(solver& s, ast_manager& m): s(s), m(m), m_cls2expr(m), m_vars(m) {}
imp(solver& s, ast_manager& m): s(s), m(m), m_cls2expr(m), m_vars(m), m_cancel(false) {}
void reset() {
m_cls2expr.reset();
m_expr2cls.reset();
m_cls2lits.reset();
m_vars.reset();
m_var2idx.reset();
}
void set_cancel(bool f) {
m_cancel = f;
}
unsigned add_var(expr* v) {
unsigned idx = m_vars.size();
@ -47,10 +59,16 @@ public:
m_cls2lits.push_back(lits);
return idx;
}
expr* mk_not(expr* e) {
if (m.is_not(e, e)) {
return e;
}
return m.mk_not(e);
}
lbool get_mus(unsigned_vector& mus) {
TRACE("opt", tout << "\n";);
solver::scoped_push _sc(s);
unsigned_vector core;
for (unsigned i = 0; i < m_cls2expr.size(); ++i) {
core.push_back(i);
@ -61,12 +79,17 @@ public:
ptr_vector<expr> core_exprs;
model.resize(m_vars.size());
while (!core.empty()) {
IF_VERBOSE(0, display_vec(tout << "core: ", core););
TRACE("opt",
display_vec(tout << "core: ", core);
display_vec(tout << "mus: ", mus);
display_vec(tout << "model: ", model);
);
IF_VERBOSE(1, verbose_stream() << "(opt.mus reducing core: " << core.size() << " new core: " << mus.size() << ")\n";);
unsigned cls_id = core.back();
core.pop_back();
expr* cls = m_cls2expr[cls_id].get();
expr_ref not_cls(m);
not_cls = m.mk_not(cls);
not_cls = mk_not(cls);
unsigned sz = assumptions.size();
assumptions.push_back(not_cls);
add_core(core, assumptions);
@ -113,7 +136,7 @@ public:
template<class T>
void display_vec(std::ostream& out, T const& v) const {
for (unsigned i = 0; i < v.size(); ++i) {
out << mk_pp(v[i], m) << " ";
out << v[i] << " ";
}
out << "\n";
}
@ -133,19 +156,18 @@ public:
*/
void rmr(unsigned_vector& M, unsigned_vector& mus, svector<bool>& model) {
TRACE("opt",
display_vec(tout << "M:", M);
display_vec(tout << "mus:", mus);
display_vec(tout << "model:", model););
display_vec(tout << "core: ", M);
display_vec(tout << "mus: ", mus);
display_vec(tout << "model: ", model););
unsigned cls_id = mus.back();
smt::literal_vector const& cls = m_cls2lits[cls_id];
unsigned cls_id_new;
for (unsigned i = 0; i < cls.size(); ++i) {
smt::literal lit = cls[i];
SASSERT(model[lit.var()] == lit.sign()); // literal evaluates to false.
model[lit.var()] = !model[lit.var()]; // swap assignment
if (has_single_unsat(model, cls_id_new)) {
mus.push_back(cls_id_new);
if (!mus.contains(cls_id) && has_single_unsat(model, cls_id)) {
mus.push_back(cls_id);
rmr(M, mus, model);
}
model[lit.var()] = !model[lit.var()]; // swap assignment back
@ -176,13 +198,6 @@ public:
return false;
}
template<class T>
void display_vec(std::ostream& out, T const& v) {
for (unsigned i = 0; i < v.size(); ++i) {
out << v[i] << " ";
}
out << "\n";
}
};
mus::mus(solver& s, ast_manager& m) {
@ -201,3 +216,10 @@ lbool mus::get_mus(unsigned_vector& mus) {
return m_imp->get_mus(mus);
}
void mus::set_cancel(bool f) {
m_imp->set_cancel(f);
}
void mus::reset() {
m_imp->reset();
}

4
src/opt/mus.h
View file

@ -16,6 +16,10 @@ namespace opt {
unsigned add_soft(expr* cls, unsigned sz, expr* const* args);
lbool get_mus(unsigned_vector& mus);
void reset();
void set_cancel(bool f);
};
};