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Fix several bugs in hyp_reducer

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- compute_marks didn't find all units
  - call to m.mk_unit_resolution expects that there is at least one unit
  - hyp-reduced proof wasn't used
  - bug in early termination
  - any hypothesis was  replaced with the old derivation of the literal
  - handle the case of a single literal premise under hypothesis that is
    replaced by an empty clause under hypothesis
This commit is contained in:
Arie Gurfinkel 2017-11-27 14:39:52 -05:00
parent 56114a5f6d
commit ab3a6702af
1 changed files with 66 additions and 18 deletions
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84
src/muz/spacer/spacer_proof_utils.cpp
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@ -326,10 +326,19 @@ class reduce_hypotheses {
m_hypmark.mark(p, true);
m_hyps.insert(m.get_fact(p));
} else {
bool hyp_mark = compute_mark1(p);
compute_mark1(p);
}
}
ProofIteratorPostOrder pit2(pr, m);
while (pit2.hasNext()) {
p = pit2.next();
if (!m.is_hypothesis(p))
{
// collect units that are hyp-free and are used as hypotheses somewhere
if (!hyp_mark && m.has_fact(p) && m_hyps.contains(m.get_fact(p)))
{ m_units.insert(m.get_fact(p), p); }
if (!m_hypmark.is_marked(p) && m.has_fact(p) && m_hyps.contains(m.get_fact(p)))
{
m_units.insert(m.get_fact(p), p);
}
}
}
}
@ -348,7 +357,7 @@ class reduce_hypotheses {
bool dirty = false;
while (!m_todo.empty()) {
proof *p, *tmp, *pp;
proof *p, *tmp, *tmp2, *pp;
unsigned todo_sz;
p = m_todo.back();
@ -377,7 +386,17 @@ class reduce_hypotheses {
if (m.is_hypothesis(p)) {
// hyp: replace by a corresponding unit
if (m_units.find(m.get_fact(p), tmp)) {
res = tmp;
// if the transformed subproof ending in the unit has already been computed, use it
if (m_cache.find(tmp,tmp2))
{
res = tmp2;
}
// otherwise first compute the transformed subproof ending in the unit
else
{
m_todo.push_back(tmp);
continue;
}
} else { res = p; }
}
@ -393,18 +412,33 @@ class reduce_hypotheses {
res = mk_unit_resolution_core(args.size(), args.c_ptr());
compute_mark1(res);
} else {
// other: reduce all premises; reapply
if (m.has_fact(p)) { args.push_back(to_app(m.get_fact(p))); }
SASSERT(p->get_decl()->get_arity() == args.size());
res = m.mk_app(p->get_decl(), args.size(), (expr * const*)args.c_ptr());
m_pinned.push_back(res);
compute_mark1(res);
// if any literal is false, we don't need a step
bool has_empty_clause_premise = false;
for (unsigned i = 0; i < args.size(); ++i)
{
if (m.is_false(m.get_fact(args[i])))
{
has_empty_clause_premise = true;
res = args[i];
}
}
// otherwise:
if (!has_empty_clause_premise)
{
// other: reduce all premises; reapply
if (m.has_fact(p)) { args.push_back(to_app(m.get_fact(p))); }
SASSERT(p->get_decl()->get_arity() == args.size());
res = m.mk_app(p->get_decl(), args.size(), (expr * const*)args.c_ptr());
m_pinned.push_back(res);
compute_mark1(res);
}
}
SASSERT(res);
m_cache.insert(p, res);
if (m.has_fact(res) && m.is_false(m.get_fact(res))) { break; }
if (!m_hypmark.is_marked(res) && m.has_fact(res) && m.is_false(m.get_fact(res))) { break; }
}
out = res;
@ -458,6 +492,15 @@ class reduce_hypotheses {
ptr_buffer<proof> pf_args;
pf_args.push_back(args [0]);
// if any literal is false, we don't need a unit resolution step
for (unsigned i = 1; i < num_args; ++i)
{
if (m.is_false(m.get_fact(args[i])))
{
return args[i];
}
}
app *cls_fact = to_app(m.get_fact(args[0]));
ptr_buffer<expr> cls;
if (m.is_or(cls_fact)) {
@ -488,9 +531,16 @@ class reduce_hypotheses {
new_fact = mk_or(m, new_fact_cls.size(), new_fact_cls.c_ptr());
// create new proof step
proof *res = m.mk_unit_resolution(pf_args.size(), pf_args.c_ptr(), new_fact);
m_pinned.push_back(res);
return res;
if (pf_args.size() == 1) // the only premise is the clause itself
{
return args[0];
}
else
{
proof *res = m.mk_unit_resolution(pf_args.size(), pf_args.c_ptr(), new_fact);
m_pinned.push_back(res);
return res;
}
}
// reduce all units, if any unit reduces to false return true and put its proof into out
@ -516,9 +566,7 @@ public:
void operator()(proof_ref &pr)
{
compute_marks(pr);
if (!reduce_units(pr)) {
reduce(pr.get(), pr);
}
reduce(pr.get(), pr);
reset();
}
};