void SimpSolver::remember(Var v)
{
assert(decisionLevel() == 0);
assert(isEliminated(v));
vec<Lit> clause;
// Re-activate variable:
elimtable[v].order = 0;
setDecisionVar(v, true); // Not good if the variable wasn't a decision variable before. Not sure how to fix this right now.
if (use_simplification)
updateElimHeap(v);
// Reintroduce all old clauses which may implicitly remember other clauses:
for (int i = 0; i < elimtable[v].eliminated.size(); i++){
Clause& c = *elimtable[v].eliminated[i];
clause.clear();
for (int j = 0; j < c.size(); j++)
clause.push(c[j]);
remembered_clauses++;
check(addClause(clause));
free(&c);
}
elimtable[v].eliminated.clear();
}
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();
}
