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Some assertions are now too strict

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If possible, we should set the new constraint to l_true;
and revert most of this change later.
Or we adjust the conflict invariant:
- l_true constraints is the default case as before,
- l_undef constraints are new and justified by some side lemma, but
  should be treated by the conflict resolution methods like l_true
  constraints,
- l_false constraints are disallowed in the conflict (as before).
This commit is contained in:
Jakob Rath 2022-10-07 16:24:14 +02:00
parent 74b53c3323
commit 23a747235d
2 changed files with 9 additions and 5 deletions
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9
src/math/polysat/conflict.cpp
View file

@ -230,8 +230,9 @@ namespace polysat {
VERIFY(false); // fail here to force check when we encounter this case
}
else {
// conflict due to assignment
SASSERT(c.bvalue(s) == l_true);
// Constraint c conflicts with the variable assignment
// SASSERT(c.bvalue(s) == l_true); // "morally" the bvalue should always be true. But (at least for now) some literals may be undef when they are only justified by a side lemma.
// TODO: maybe we can set them to true (without putting them on the search stack). But need to make sure to set them to false when finalizing the conflict; and before backjumping/learning. (tag:true_by_side_lemma)
SASSERT(c.is_currently_false(s));
insert(c);
insert_vars(c);
@ -291,7 +292,7 @@ namespace polysat {
if (c.is_always_true())
return;
LOG("Inserting " << lit_pp(s, c));
SASSERT_EQ(c.bvalue(s), l_true);
// SASSERT_EQ(c.bvalue(s), l_true); // TODO: see comment in 'set_impl' (tag:true_by_side_lemma)
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());
@ -328,6 +329,7 @@ namespace polysat {
clause_ref lemma = cb.build();
SASSERT(lemma);
lemma->set_redundant(true);
LOG("Side lemma: " << *lemma);
m_lemmas.push_back(std::move(lemma));
}
@ -596,6 +598,7 @@ namespace polysat {
out << " bail vars";
for (auto v : m_bail_vars)
out << " v" << v;
// TODO: side lemmas?
return out;
}
}

5
src/math/polysat/explain.cpp
View file

@ -69,7 +69,8 @@ namespace polysat {
SASSERT(c1.is_currently_true(s));
SASSERT(c2.is_currently_false(s));
SASSERT_EQ(c1.bvalue(s), l_true);
SASSERT_EQ(c2.bvalue(s), l_true);
// SASSERT_EQ(c2.bvalue(s), l_true); // TODO: should always be l_true but currently it's not guaranteed if c2 was derived via side lemma (tag:true_by_side_lemma)
SASSERT(c2.bvalue(s) != l_false);
signed_constraint c = resolve1(v, c1, c2);
if (!c)
@ -93,7 +94,7 @@ namespace polysat {
// c should be unit-propagated to l_true by c1 /\ c2 ==> c
core.add_lemma({c, ~c1, ~c2});
core.log_inference(inference_sup("l_undef lemma", v, c2, c1));
SASSERT_EQ(l_true, c.bvalue(s));
// SASSERT_EQ(l_true, c.bvalue(s)); // not true anymore (TODO: but it should be) (tag:true_by_side_lemma)
break;
case l_true:
// c is just another constraint on the search stack; could be equivalent or better