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Handle conversion of quantified lemma to quantifier free

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When a cube is updated, a lemma might loose all of its quantified
variables. In this case, it is effectively quantifier free
and might be a version of an already existing lemma.

For that reason, we convert it to quantifier free lemma when
this happens.
This commit is contained in:
Arie Gurfinkel 2017-12-29 12:03:48 -05:00
parent 23a8e59493
commit 9cdb63ae4a
2 changed files with 23 additions and 8 deletions
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14
src/muz/spacer/spacer_context.cpp
View file

@ -1300,6 +1300,18 @@ void lemma::update_cube (pob_ref const &p, expr_ref_vector &cube) {
m_body.reset();
m_cube.append(cube);
if (m_cube.empty()) {m_cube.push_back(m.mk_true());}
// after the cube is updated, if there are no skolems,
// convert the lemma to quantifier-free
bool is_quant = false;
for (unsigned i = 0, sz = cube.size(); !is_quant && i < sz; ++i) {
is_quant = has_zk_const(cube.get(i));
}
if (!is_quant) {
m_zks.reset();
m_bindings.reset();
}
}
bool lemma::has_binding(app_ref_vector const &binding) {
@ -2272,7 +2284,7 @@ void context::init_lemma_generalizers(datalog::rule_set& rules)
}
if (m_params.spacer_use_quant_generalizer()) {
m_lemma_generalizers.push_back(alloc(lemma_bool_inductive_generalizer, *this, 0, false));
m_lemma_generalizers.push_back(alloc(lemma_bool_inductive_generalizer, *this, 0, true));
m_lemma_generalizers.push_back(alloc(lemma_quantifier_generalizer, *this));
}

17
src/muz/spacer/spacer_quant_generalizer.cpp
View file

@ -202,7 +202,11 @@ void lemma_quantifier_generalizer::find_matching_expressions(
sem_matcher match(m);
bool pos;
substitution v_sub(m);
v_sub.reserve(2, subs.size()+1);
// allocate space for the largest variable in the pattern
unsigned max_idx = 0;
for (var* v : subs) {max_idx = std::max(max_idx, v->get_idx());}
v_sub.reserve(2, max_idx + 1);
if (!match(pattern, lit, v_sub, pos)) {
continue;
@ -378,13 +382,15 @@ void lemma_quantifier_generalizer::operator()(lemma_ref &lemma) {
TRACE("spacer_qgen",
tout << "initial cube: " << mk_and(lemma->get_cube()) << "\n";);
if (false) {
if (true) {
// -- re-normalize the cube
expr_ref c(m);
c = mk_and(cube);
normalize(c, c, true, true);
cube.reset();
flatten_and(c, cube);
TRACE("spacer_qgen",
tout << "normalized cube:\n" << mk_and(cube) << "\n";);
}
app_ref_vector skolems(m);
@ -398,10 +404,6 @@ void lemma_quantifier_generalizer::operator()(lemma_ref &lemma) {
// generate candidates
app_ref_vector candidates(m);
find_candidates(r, candidates);
// XXX Can candidates be empty and arguments not empty?
// XXX Why separate candidates and arguments?
// XXX Why are arguments processed before candidates?
if (candidates.empty()) continue;
@ -456,7 +458,7 @@ void lemma_quantifier_generalizer::operator()(lemma_ref &lemma) {
unsigned weakness = lemma->weakness();
pred_transformer &pt = lemma->get_pob()->pt();
if (pt.check_inductive(lemma->level(), new_cube, uses_level, weakness)) {
TRACE("spacer",
TRACE("spacer_qgen",
tout << "Quantifier Generalization Succeeded!\n"
<< "New CUBE is: " << mk_pp(mk_and(new_cube),m) << "\n";);
SASSERT(zks.size() >= offset);
@ -482,6 +484,7 @@ void lemma_quantifier_generalizer::operator()(lemma_ref &lemma) {
lemma->update_cube(lemma->get_pob(), new_cube);
lemma->set_level(uses_level);
SASSERT(offset + 1 == zks.size());
// XXX Assumes that offset + 1 == zks.size();
for (unsigned sk=offset; sk < zks.size(); sk++)
lemma->add_skolem(zks.get(sk), to_app(bind));