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Remove old code

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backjump_lemma, revert_decision, revert_bool_decision
This commit is contained in:
Jakob Rath 2022-11-30 12:21:39 +01:00
parent b4b94c954b
commit 54a21e764d
1 changed files with 9 additions and 91 deletions
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100
src/math/polysat/solver.cpp
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@ -782,101 +782,19 @@ namespace polysat {
report_unsat();
}
#if 0
/**
* Simple backjumping for lemmas:
* jump to the level where the lemma can be (bool-)propagated,
* even without reverting the last decision.
*/
void solver::backjump_lemma() {
clause_ref lemma = m_conflict.build_lemma();
LOG_H2("backjump_lemma: " << show_deref(lemma));
SASSERT(lemma);
// find second-highest level of the literals in the lemma
unsigned max_level = 0;
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());
backjump_and_learn(jump_level, *lemma);
}
#endif
/**
* Revert a decision that caused a conflict.
* Variable v was assigned by a decision at position i in the search stack.
*
* C & v = val is conflict.
*
* C => v != val
*
* l1 \/ l2 \/ ... \/ lk \/ v != val
*
*/
void solver::revert_decision(pvar v) {
#if 0
rational val = m_value[v];
LOG_H2("Reverting decision: pvar " << v << " := " << val);
SASSERT(m_justification[v].is_decision());
clause_ref lemma = m_conflict.build_lemma();
SASSERT(lemma);
if (lemma->empty()) {
report_unsat();
return;
}
unsigned jump_level = get_level(v) - 1;
backjump_and_learn(jump_level, *lemma);
#endif
unsigned max_jump_level = get_level(v) - 1;
backjump_and_learn(max_jump_level);
}
void solver::revert_bool_decision(sat::literal const lit) {
#if 0
LOG_H2("Reverting decision: " << lit_pp(*this, lit));
sat::bool_var const var = lit.var();
clause_ref lemma_ref = m_conflict.build_lemma();
SASSERT(lemma_ref);
clause& lemma = *lemma_ref;
SASSERT(!lemma.empty());
SASSERT(count(lemma, ~lit) > 0);
SASSERT(all_of(lemma, [this](sat::literal lit1) { return m_bvars.is_false(lit1); }));
SASSERT(all_of(lemma, [this, var](sat::literal lit1) { return var == lit1.var() || m_bvars.level(lit1) < m_bvars.level(var); }));
unsigned jump_level = m_bvars.level(var) - 1;
backjump_and_learn(jump_level, lemma);
// At this point, the lemma is asserting for ~lit,
// and has been propagated by learn_lemma/add_clause.
SASSERT(all_of(lemma, [this](sat::literal lit1) { return m_bvars.is_assigned(lit1); }));
// so the regular propagation loop will propagate ~lit.
// Recall that lit comes from a non-asserting lemma.
// If there is more than one undef choice left in that lemma,
// then the next bdecide will take care of that (after all outstanding propagations).
SASSERT(can_bdecide());
#endif
unsigned max_jump_level = m_bvars.level(lit) - 1;
backjump_and_learn(max_jump_level);
}
std::optional<lemma_score> solver::compute_lemma_score(clause const& lemma) {
unsigned max_level = 0; // highest level in lemma
unsigned at_max_level = 0; // how many literals at the highest level in lemma
unsigned lits_at_max_level = 0; // how many literals at the highest level in lemma
unsigned snd_level = 0; // second-highest level in lemma
for (sat::literal lit : lemma) {
SASSERT(m_bvars.is_assigned(lit)); // any new constraints should have been assign_eval'd
@ -887,14 +805,14 @@ namespace polysat {
if (lit_level > max_level) {
snd_level = max_level;
max_level = lit_level;
at_max_level = 1;
} else if (lit_level == max_level) {
at_max_level++;
} else if (max_level > lit_level && lit_level > snd_level) {
snd_level = lit_level;
lits_at_max_level = 1;
}
else if (lit_level == max_level)
lits_at_max_level++;
else if (max_level > lit_level && lit_level > snd_level)
snd_level = lit_level;
}
SASSERT(lemma.empty() || at_max_level > 0);
SASSERT(lemma.empty() || lits_at_max_level > 0);
// The MCSAT paper distinguishes between "UIP clauses" and "semantic split clauses".
// It is the same as our distinction between "asserting" and "non-asserting" lemmas.
// - UIP clause: a single literal on the highest decision level in the lemma.
@ -903,11 +821,11 @@ namespace polysat {
// Backtrack to "highest level - 1" and split on the lemma there.
// For now, we follow the same convention for computing the jump levels.
unsigned jump_level;
if (at_max_level <= 1)
if (lits_at_max_level <= 1)
jump_level = snd_level;
else
jump_level = (max_level == 0) ? 0 : (max_level - 1);
return {{jump_level, at_max_level}};
return {{jump_level, lits_at_max_level}};
}
void solver::backjump_and_learn(unsigned max_jump_level) {