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simplify and fix final check operations

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This commit is contained in:
Nikolaj Bjorner 2023-12-21 09:26:29 -08:00
parent 2427cd5d33
commit 2932b63b1a
2 changed files with 44 additions and 17 deletions
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59
src/sat/smt/polysat/core.cpp
View file

@ -193,6 +193,31 @@ namespace polysat {
}
sat::check_result core::final_check() {
constraint_id conflict_idx = find_conflicting_constraint();
// If all constraints evaluate to true, we are done.
if (conflict_idx.is_null())
return sat::check_result::CR_DONE;
// Extract variables that are of level or above of conflicting constraint and contradict the constraint
auto vars = find_conflict_variables(conflict_idx);
saturation sat(*this);
for (auto v: vars)
if (sat.propagate(v, conflict_idx))
return sat::check_result::CR_CONTINUE;
// If no saturation propagation was possible, explain the conflict using the variable assignment.
m_unsat_core = explain_eval(get_constraint(conflict_idx));
m_unsat_core.push_back(conflict_idx);
propagate_unsat_core();
return sat::check_result::CR_CONTINUE;
}
/**
* Identify a conflicting constraint, if any, that evaluates to false under
* the current assignment.
*/
constraint_id core::find_conflicting_constraint() {
unsigned conflict_level = UINT_MAX;
constraint_id conflict_idx = { UINT_MAX };
for (auto idx : m_prop_queue) {
@ -203,37 +228,37 @@ namespace polysat {
if (eval_value == value)
continue;
auto explain = explain_eval(sc);
unsigned new_conflict_level = d.level();
unsigned new_conflict_level = d.level();
for (auto idx2 : explain)
new_conflict_level = std::max(new_conflict_level, m_constraint_index[idx2.id].d.level());
if (new_conflict_level >= conflict_level)
continue;
conflict_idx = idx;
conflict_level = new_conflict_level;
conflict_level = new_conflict_level;
}
if (conflict_level == UINT_MAX)
return sat::check_result::CR_DONE;
auto [sc, d, value] = m_constraint_index[conflict_idx.id];
pvar max_var = UINT_MAX;
unsigned lvl = 0;
return conflict_idx;
}
/**
* Find variables at the maximal scope level that are used in the conflicting literal.
*/
svector<pvar> core::find_conflict_variables(constraint_id idx) {
svector<pvar> result;
auto [sc, d, value] = m_constraint_index[idx.id];
unsigned lvl = d.level();
for (auto v : sc.vars()) {
if (!is_assigned(v))
continue;
auto new_level = m_constraint_index[m_justification[v].id].d.level();
if (new_level > lvl)
if (new_level < lvl)
continue;
max_var = v;
if (new_level > lvl)
result.reset();
result.push_back(v);
lvl = new_level;
}
saturation sat(*this);
if (sat.propagate(max_var, conflict_idx))
return sat::check_result::CR_CONTINUE;
m_unsat_core = explain_eval(sc);
m_unsat_core.push_back(conflict_idx);
propagate_unsat_core();
return sat::check_result::CR_CONTINUE;
return result;
}
// First propagate Boolean assignment, then propagate value assignment

2
src/sat/smt/polysat/core.h
View file

@ -95,6 +95,8 @@ namespace polysat {
dependency_vector get_dependencies(std::initializer_list<constraint_id> const& cc);
sat::check_result final_check();
constraint_id find_conflicting_constraint();
svector<pvar> find_conflict_variables(constraint_id idx);
void add_axiom(signed_constraint sc);