bool SimpSMTSolver::eliminateVar(Var v, bool fail)
{
if (!fail && asymm_mode && !asymmVar(v)) return false;
const vec<Clause*>& cls = getOccurs(v);
// if (value(v) != l_Undef || cls.size() == 0) return true;
if (value(v) != l_Undef) return true;
// Split the occurrences into positive and negative:
vec<Clause*> pos, neg;
for (int i = 0; i < cls.size(); i++)
(find(*cls[i], Lit(v)) ? pos : neg).push(cls[i]);
// Check if number of clauses decreases:
int cnt = 0;
for (int i = 0; i < pos.size(); i++)
for (int j = 0; j < neg.size(); j++)
if (merge(*pos[i], *neg[j], v) && ++cnt > cls.size() + grow)
return true;
#ifdef PEDANTIC_DEBUG
cerr << "XXY gonna-remove" << endl;
#endif
// Delete and store old clauses:
setDecisionVar(v, false);
elimtable[v].order = elimorder++;
assert(elimtable[v].eliminated.size() == 0);
for (int i = 0; i < cls.size(); i++)
{
elimtable[v].eliminated.push(Clause_new(*cls[i]));
removeClause(*cls[i]);
}
// Produce clauses in cross product:
int top = clauses.size();
vec<Lit> resolvent;
for (int i = 0; i < pos.size(); i++)
for (int j = 0; j < neg.size(); j++)
if (merge(*pos[i], *neg[j], v, resolvent) && !addClause(resolvent))
return false;
// DEBUG: For checking that a clause set is saturated with respect to variable elimination.
// If the clause set is expected to be saturated at this point, this constitutes an
// error.
if (fail){
reportf("eliminated var %d, %d <= %d\n", v+1, cnt, cls.size());
reportf("previous clauses:\n");
for (int i = 0; i < cls.size(); i++){
printClause(*cls[i]); reportf("\n"); }
reportf("new clauses:\n");
for (int i = top; i < clauses.size(); i++){
printClause(*clauses[i]); reportf("\n"); }
assert(0); }
return backwardSubsumptionCheck();
}
bool SimpSolver::asymmVar(Var v)
{
assert(!frozen[v]);
assert(use_simplification);
vec<Clause*> pos, neg;
const vec<Clause*>& cls = getOccurs(v);
if (value(v) != l_Undef || cls.size() == 0)
return true;
for (int i = 0; i < cls.size(); i++)
if (!asymm(v, *cls[i]))
return false;
return backwardSubsumptionCheck();
}
bool SimpSolver::eliminate(bool turn_off_elim)
{
if (!ok || !use_simplification)
return ok;
// Main simplification loop:
//assert(subsumption_queue.size() == 0);
//gatherTouchedClauses();
while (subsumption_queue.size() > 0 || elim_heap.size() > 0){
//fprintf(stderr, "subsumption phase: (%d)\n", subsumption_queue.size());
if (!backwardSubsumptionCheck(true))
return false;
//fprintf(stderr, "elimination phase:\n (%d)", elim_heap.size());
for (int cnt = 0; !elim_heap.empty(); cnt++){
Var elim = elim_heap.removeMin();
if (verbosity >= 2 && cnt % 100 == 0)
reportf("elimination left: %10d\r", elim_heap.size());
if (!frozen[elim] && !eliminateVar(elim))
return false;
}
assert(subsumption_queue.size() == 0);
gatherTouchedClauses();
}
// Cleanup:
cleanUpClauses();
order_heap.filter(VarFilter(*this));
#ifdef INVARIANTS
// Check that no more subsumption is possible:
reportf("Checking that no more subsumption is possible\n");
for (int i = 0; i < clauses.size(); i++){
if (i % 1000 == 0)
reportf("left %10d\r", clauses.size() - i);
assert(clauses[i]->mark() == 0);
for (int j = 0; j < i; j++)
assert(clauses[i]->subsumes(*clauses[j]) == lit_Error);
}
reportf("done.\n");
// Check that no more elimination is possible:
reportf("Checking that no more elimination is possible\n");
for (int i = 0; i < nVars(); i++)
if (!frozen[i]) eliminateVar(i, true);
reportf("done.\n");
checkLiteralCount();
#endif
// If no more simplification is needed, free all simplification-related data structures:
if (turn_off_elim){
use_simplification = false;
touched.clear(true);
occurs.clear(true);
n_occ.clear(true);
subsumption_queue.clear(true);
elim_heap.clear(true);
remove_satisfied = true;
}
return true;
}
