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Add level to conflict

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- reset conflict at correct level when popping user scopes
- functions as flag when handling inconsistent input (e.g., opposite literals)
- now all constraints in the conflict core should have bvalue == l_true
This commit is contained in:
Jakob Rath 2022-09-23 15:54:37 +02:00
parent 86d00b536a
commit a4f0e3a228
5 changed files with 87 additions and 28 deletions
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50
src/math/polysat/conflict.cpp
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@ -140,10 +140,14 @@ namespace polysat {
}
bool conflict::empty() const {
return m_literals.empty()
&& m_vars.empty()
&& m_bail_vars.empty()
&& m_lemmas.empty();
bool const is_empty = (m_level == UINT_MAX);
if (is_empty) {
SASSERT(m_literals.empty());
SASSERT(m_vars.empty());
SASSERT(m_bail_vars.empty());
SASSERT(m_lemmas.empty());
}
return is_empty;
}
void conflict::reset() {
@ -154,6 +158,7 @@ namespace polysat {
m_var_occurrences.reset();
m_lemmas.reset();
m_kind = conflict_kind_t::ok;
m_level = UINT_MAX;
SASSERT(empty());
}
@ -182,7 +187,6 @@ namespace polysat {
return true;
case conflict_kind_t::backtrack:
return pvar_occurs_in_constraints(v) || m_relevant_vars.contains(v);
// return m_relevant_vars.contains(v);
case conflict_kind_t::backjump:
UNREACHABLE(); // we don't follow the regular loop when backjumping
return false;
@ -195,8 +199,30 @@ namespace polysat {
return contains(lit) || contains(~lit);
}
void conflict::init_at_base_level() {
SASSERT(empty());
SASSERT(s.at_base_level());
m_level = s.m_level;
SASSERT(!empty());
}
void conflict::init(signed_constraint c) {
SASSERT(empty());
m_level = s.m_level;
/*
// NOTE: c.is_always_false() may happen e.g. if we add an always false constraint in the input
if (c.is_always_false()) {
SASSERT(c.bvalue(s) == l_true);
SASSERT(s.m_bvars.is_assumption(c.blit()));
SASSERT(s.at_base_level());
// TODO: this kind of constraint should be handled when it is being added to the solver.
return;
}
if (c.bvalue(s) == l_false && s.at_base_level()) {
// We have opposite literals in the input.
return;
}
*/
set_impl(c);
logger().begin_conflict();
}
@ -238,6 +264,7 @@ namespace polysat {
// return;
// LOG("Conflict: " << cl);
SASSERT(empty());
m_level = s.m_level;
for (auto lit : cl) {
auto c = s.lit2cnstr(lit);
SASSERT(c.bvalue(s) == l_false);
@ -248,6 +275,8 @@ namespace polysat {
}
void conflict::init(pvar v, bool by_viable_fallback) {
SASSERT(empty());
m_level = s.m_level;
if (by_viable_fallback) {
logger().begin_conflict(header_with_var("unsat core from viable fallback for v", v));
// Conflict detected by viable fallback:
@ -264,6 +293,7 @@ namespace polysat {
// but each branch exclude the current assignment.
// in those cases we will (additionally?) need an abstraction that is asserting to make sure viable is updated properly.
}
SASSERT(!empty());
}
bool conflict::contains(sat::literal lit) const {
@ -276,7 +306,8 @@ namespace polysat {
return;
if (c.is_always_true())
return;
LOG("Inserting: " << c);
LOG("Inserting " << lit_pp(s, c));
SASSERT(c.bvalue(s) == l_true);
SASSERT(!c.is_always_false()); // if we added c, the core would be a tautology
SASSERT(!c->vars().empty());
m_literals.insert(c.blit().index());
@ -424,9 +455,12 @@ namespace polysat {
LOG("core: " << *this);
clause_builder lemma(s);
// TODO: is this sound, doing it for each constraint separately?
for (auto c : *this)
#if 0
if (m_literals.size() == 1) {
auto c = *begin();
minimize_vars(c);
}
#endif
for (auto c : *this)
lemma.push(~c);