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bailout for saturation lemmas

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This commit is contained in:
Jakob Rath 2022-07-01 11:51:52 +02:00
parent c78007fd1a
commit d473c23e5b
5 changed files with 89 additions and 24 deletions
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49
src/math/polysat/solver.cpp
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@ -27,8 +27,6 @@ Author:
namespace polysat {
solver::solver(reslimit& lim):
m_lim(lim),
m_viable(*this),
@ -93,7 +91,6 @@ namespace polysat {
return check_sat();
}
dd::pdd_manager& solver::sz2pdd(unsigned sz) const {
m_pdd.reserve(sz + 1);
if (!m_pdd[sz])
@ -643,6 +640,11 @@ namespace polysat {
revert_decision(v);
return;
}
if (m_conflict.is_bailout_lemma()) {
m_conflict.end_conflict();
backtrack_lemma();
return;
}
m_search.pop_assignment();
}
else {
@ -677,7 +679,44 @@ namespace polysat {
}
/**
* Simpler backracking for forbidden interval lemmas:
* Simple backtracking for lemmas:
* jump to the level where the lemma can be (bool-)propagated,
* even without reverting the last decision.
*/
void solver::backtrack_lemma() {
clause_ref lemma = m_conflict.build_lemma().build();
LOG_H2("backtrack_lemma: " << show_deref(lemma));
SASSERT(lemma);
// find second-highest level of the literals in the lemma
unsigned max_level = 0; // could be simplified if we're sure that always max_level == m_level
unsigned jump_level = 0;
for (auto lit : *lemma) {
if (!m_bvars.is_assigned(lit))
continue;
unsigned lit_level = m_bvars.level(lit);
if (lit_level > max_level) {
jump_level = max_level;
max_level = lit_level;
} else if (max_level > lit_level && lit_level > jump_level) {
jump_level = lit_level;
}
}
jump_level = std::max(jump_level, base_level());
// LOG("current lvl: " << m_level);
// LOG("base level: " << base_level());
// LOG("max_level: " << max_level);
// LOG("jump_level: " << jump_level);
m_conflict.reset();
backjump(jump_level);
learn_lemma(*lemma);
}
/**
* Simpler backtracking for forbidden interval lemmas:
* since forbidden intervals already gives us a lemma where the conflict variable has been eliminated,
* we can backtrack to the last relevant decision and learn this lemma.
*/
@ -914,7 +953,7 @@ namespace polysat {
LOG_H3("Reverting boolean decision: " << lit << " " << m_conflict);
SASSERT(m_bvars.is_decision(var));
clause_builder reason_builder = m_conflict.build_lemma();
clause_builder reason_builder = m_conflict.build_lemma();
SASSERT(std::find(reason_builder.begin(), reason_builder.end(), ~lit));
clause_ref reason = reason_builder.build();