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Track max jump level from side lemmas

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This commit is contained in:
Jakob Rath 2022-11-14 15:43:46 +01:00
parent cd83a6ec69
commit aa59de9056
2 changed files with 37 additions and 0 deletions
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29
src/math/polysat/conflict.cpp
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@ -38,6 +38,8 @@ TODO:
- it is not sound to do minimization for each constraint separately, if there are multiple constraints.
- condition `c.is_currently_false(s, a)` is too weak (need also `c.bvalue(s) == l_true`?)
- we are missing a stopping criterion like "first UIP" in SAT solving. Currently we always resolve backwards until the decision.
--*/
#include "math/polysat/conflict.h"
@ -152,6 +154,7 @@ namespace polysat {
SASSERT(m_vars_occurring.empty());
SASSERT(m_lemmas.empty());
SASSERT(m_narrow_queue.empty());
SASSERT_EQ(m_max_jump_level, UINT_MAX);
}
return is_empty;
}
@ -166,6 +169,7 @@ namespace polysat {
m_narrow_queue.reset();
m_kind = conflict_kind_t::ok;
m_level = UINT_MAX;
m_max_jump_level = UINT_MAX;
SASSERT(empty());
}
@ -333,6 +337,31 @@ namespace polysat {
for (sat::literal lit : *lemma) {
LOG(" " << lit_pp(s, lit));
}
// Two kinds of side lemmas:
// 1. If all constraints are false, then the side lemma is an alternative conflict lemma.
// => we should at least jump back to the second-highest level in the lemma (could be lower, if so justified by another lemma)
// 2. If there is an undef constraint, then it is is a justification for this new constraint.
// (Can there be more than one undef constraint? Should not happen for these lemmas.)
// => TODO: (unclear) jump at least to the max level in the lemma and hope the propagation helps there? or ignore it for jump level computation?
unsigned max_level = 0; // highest level in lemma
unsigned jump_level = 0; // second-highest level in lemma
bool has_unassigned = false;
for (sat::literal lit : *lemma) {
if (!s.m_bvars.is_assigned(lit)) {
has_unassigned = true;
continue;
}
unsigned const lit_level = s.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;
}
}
if (has_unassigned)
jump_level = max_level;
m_max_jump_level = std::min(m_max_jump_level, jump_level);
m_lemmas.push_back(std::move(lemma));
// If possible, we should set the new constraint to l_true;
// and re-enable the assertions marked with "tag:true_by_side_lemma".