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introducing scoped detacth/attach of clauses to enforce basic sat solver invariants. Part of investigating #939:

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-03-22 14:12:47 -07:00
parent 25d839ed10
commit e47e8c67c0
5 changed files with 42 additions and 24 deletions
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11
src/sat/sat_asymm_branch.cpp
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@ -96,7 +96,6 @@ namespace sat {
if (!process(c))
continue; // clause was removed
*it2 = *it;
// throw exception to test bug fix: if (it2 != it) throw solver_exception("trigger bug");
++it2;
}
s.m_clauses.set_end(it2);
@ -129,14 +128,14 @@ namespace sat {
// check if the clause is already satisfied
for (i = 0; i < sz; i++) {
if (s.value(c[i]) == l_true) {
s.dettach_clause(c);
s.detach_clause(c);
s.del_clause(c);
return false;
}
}
// try asymmetric branching
// clause must not be used for propagation
s.dettach_clause(c);
solver::scoped_detach scoped_d(s, c);
s.push();
for (i = 0; i < sz - 1; i++) {
literal l = c[i];
@ -154,7 +153,6 @@ namespace sat {
SASSERT(s.m_qhead == s.m_trail.size());
if (i == sz - 1) {
// clause size can't be reduced.
s.attach_clause(c);
return true;
}
// clause can be reduced
@ -189,18 +187,17 @@ namespace sat {
TRACE("asymm_branch", tout << "produced unit clause: " << c[0] << "\n";);
s.assign(c[0], justification());
s.propagate_core(false);
s.del_clause(c);
scoped_d.del_clause();
SASSERT(s.inconsistent() || s.m_qhead == s.m_trail.size());
return false; // check_missed_propagation() may fail, since m_clauses is not in a consistent state.
case 2:
SASSERT(s.value(c[0]) == l_undef && s.value(c[1]) == l_undef);
s.mk_bin_clause(c[0], c[1], false);
s.del_clause(c);
scoped_d.del_clause();
SASSERT(s.m_qhead == s.m_trail.size());
return false;
default:
c.shrink(new_sz);
s.attach_clause(c);
SASSERT(s.m_qhead == s.m_trail.size());
return true;
}