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resurrect Booelan decisions to deal with quot-rem and similar axioms

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2022-01-27 14:26:41 -08:00
parent be790b8892
commit ff4b471f93
4 changed files with 30 additions and 21 deletions
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39
src/math/polysat/solver.cpp
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@ -150,20 +150,13 @@ namespace polysat {
add_eq(b * q + r - a);
add_noovfl(b, q);
add_ule(r, b*q+r);
auto c1 = eq(b);
auto c2 = ult(r, b);
auto c3 = diseq(b);
auto c4 = eq(q + 1);
add_clause(c1, c2, false);
add_clause(c3, c4, false);
// BUG:
// need to watch these constraints.
// ... but activation discipline seems to
// work only for lemmas. Literals are watched only when assigned true.
// The literals are de-activated
// after propagation
// Should these clauses then be added as lemmas that force a branch?
auto c_eq = eq(b);
add_clause(c_eq, ult(r, b), false);
add_clause(~c_eq, eq(q + 1), false);
// force decisions on whether b == 0
m_bvars.track_var(c_eq.blit());
return std::tuple<pdd, pdd>(q, r);
}
@ -449,7 +442,10 @@ namespace polysat {
void solver::decide() {
LOG_H2("Decide");
SASSERT(can_decide());
pdecide(m_free_pvars.next_var());
if (!m_free_pvars.empty())
pdecide(m_free_pvars.next_var());
else
bdecide(m_bvars.next_var());
}
void solver::pdecide(pvar v) {
@ -472,9 +468,16 @@ namespace polysat {
push_level();
assign_core(v, val, justification::decision(m_level));
break;
}
}
}
void solver::bdecide(sat::bool_var b) {
sat::literal lit(b);
m_bvars.decide(lit, m_level);
m_trail.push_back(trail_instr_t::assign_bool_i);
m_search.push_boolean(lit);
}
void solver::assign_core(pvar v, rational const& val, justification const& j) {
if (j.is_decision())
++m_stats.m_num_decisions;
@ -766,16 +769,14 @@ namespace polysat {
// The lemma where 'lit' comes from.
// Currently, boolean decisions always come from guessing a literal of a learned non-unit lemma.
clause* lemma = m_bvars.lemma(var); // need to grab this while 'lit' is still assigned
// We only revert decisions that come from lemmas, so lemma must not be NULL here.
// (Externally asserted literals are at a base level, so we would return UNSAT instead of reverting.)
SASSERT(lemma);
backjump(m_bvars.level(var) - 1);
// reason should force ~lit after propagation
add_clause(*reason);
enqueue_decision_on_lemma(*lemma);
if (lemma)
enqueue_decision_on_lemma(*lemma);
}
unsigned solver::level(sat::literal lit0, clause const& cl) {