boost::unordered_set<Model> MCSat::sampleSat(const Model& initialModel, const Domain& d, boost::mt19937& rng) {
boost::unordered_set<Model> models;
models.insert(initialModel); // always include the initial model
// transform domain into a SAT problem
Domain dSat;
for (Domain::fact_const_iterator it = d.facts_begin(); it != d.facts_end(); it++) {
dSat.addFact(*it);
}
for (Domain::formula_const_iterator it = d.formulas_begin(); it != d.formulas_end(); it++) {
ELSentence s = *it;
s.setHasInfWeight(true);
dSat.addFormula(s);
}
dSat.addAtoms(d.atoms_begin(), d.atoms_end());
// perform UP (if possible)
Domain reduced;
if (useUnitPropagation_) {
try {
reduced = MCSat::applyUP(dSat);
} catch (contradiction& c) {
return models; // can't continue, just return our models which has only one item.
}
} else {
reduced = dSat;
}
// rewrite infinite weighted formulas so they have singular weight
reduced = reduced.replaceInfForms();
// do some random restarts and hope for different models
MWSSolver walksatSolver(walksatIterations_, walksatRandomMoveProb_, &reduced);
for (unsigned int i = 1; i <= walksatNumRandomRestarts_; i++) {
Model iterInitModel = reduced.randomModel(rng); // TODO: better way to make random models
if (reduced.formulas_size() == 0) {
// just add the random model and continue
models.insert(reduced.randomModel(rng));
continue;
}
//std::cout << "--\nFormulas for maxwalksat: ";
//std::copy(reduced.formulas_begin(), reduced.formulas_end(), std::ostream_iterator<ELSentence>(std::cout, ", "));
//std::cout << std::endl;
Model iterModel = walksatSolver.run(rng, iterInitModel);
if (reduced.isFullySatisfied(iterModel)) models.insert(iterModel);
}
return models;
}
Domain MCSat::applyUP(const Domain& d) {
Domain reduced;
try {
reduced = performUnitPropagation(d);
} catch (contradiction& c) {
// rewrite error message
throw contradiction("Contradiction found in MCSat::run() when running unit prop()");
}
// default model is guaranteed to satisfy the facts
Model m = reduced.defaultModel();
// check to make sure hard clauses are satisfied
std::vector<ELSentence> hardClauses;
std::remove_copy_if(reduced.formulas_begin(), reduced.formulas_end(), std::back_inserter(hardClauses), std::not1(IsHardClausePred()));
for (std::vector<ELSentence>::const_iterator it = hardClauses.begin(); it != hardClauses.end(); it++) {
if (!it->fullySatisfied(m, reduced)) {
throw contradiction("Contradiction found in MCSat::run() when verifying hard clauses are satisfied");
}
}
return reduced;
}
