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Fix bug in qe_term_graph

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In merge, parents of A instead of parents of B were traversed.
Among other things, it created stale marks that caused an
infinite loop in to_lits()
This commit is contained in:
Arie Gurfinkel 2018-06-27 22:45:38 -04:00
parent 0e5434ce0c
commit 4abab8aaf5
2 changed files with 19 additions and 9 deletions
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27
src/qe/qe_term_graph.cpp
View file

@ -200,7 +200,8 @@ namespace qe {
} }
std::ostream& display(std::ostream& out) const { std::ostream& display(std::ostream& out) const {
out << get_id() << ": " << m_expr << " - "; out << get_id() << ": " << m_expr
<< (is_root() ? " R" : "") << " - ";
term const* r = &this->get_next(); term const* r = &this->get_next();
while (r != this) { while (r != this) {
out << r->get_id() << " "; out << r->get_id() << " ";
@ -371,20 +372,20 @@ namespace qe {
} }
void term_graph::merge(term &t1, term &t2) { void term_graph::merge(term &t1, term &t2) {
// -- merge might invalidate term2app cache
m_term2app.reset();
m_pinned.reset();
term *a = &t1.get_root(); term *a = &t1.get_root();
term *b = &t2.get_root(); term *b = &t2.get_root();
if (a == b) return; if (a == b) return;
// -- merge might invalidate term2app cache
m_term2app.reset();
m_pinned.reset();
if (a->get_class_size() > b->get_class_size()) { if (a->get_class_size() > b->get_class_size()) {
std::swap(a, b); std::swap(a, b);
} }
// Remove parents of it from the cg table. // Remove parents of b from the cg table.
for (term* p : term::parents(b)) { for (term* p : term::parents(b)) {
if (!p->is_marked()) { if (!p->is_marked()) {
p->set_mark(true); p->set_mark(true);
@ -401,7 +402,7 @@ namespace qe {
a->merge_eq_class(*b); a->merge_eq_class(*b);
// Insert parents of b's old equilvalence class into the cg table // Insert parents of b's old equilvalence class into the cg table
for (term* p : term::parents(a)) { for (term* p : term::parents(b)) {
if (p->is_marked()) { if (p->is_marked()) {
term* p_old = m_cg_table.insert_if_not_there(p); term* p_old = m_cg_table.insert_if_not_there(p);
p->set_mark(false); p->set_mark(false);
@ -412,6 +413,7 @@ namespace qe {
} }
} }
} }
SASSERT(marks_are_clear());
} }
expr* term_graph::mk_app_core (expr *e) { expr* term_graph::mk_app_core (expr *e) {
@ -484,10 +486,16 @@ namespace qe {
} }
} }
bool term_graph::marks_are_clear() {
for (term * t : m_terms) {
if (t->is_marked()) return false;
}
return true;
}
/// Order of preference for roots of equivalence classes /// Order of preference for roots of equivalence classes
/// XXX This should be factored out to let clients control the preference /// XXX This should be factored out to let clients control the preference
bool term_graph::term_lt(term const &t1, term const &t2) { bool term_graph::term_lt(term const &t1, term const &t2) {
// prefer constants over applications // prefer constants over applications
// prefer uninterpreted constants over values // prefer uninterpreted constants over values
// prefer smaller expressions over larger ones // prefer smaller expressions over larger ones
@ -521,6 +529,7 @@ namespace qe {
/// Choose better roots for equivalence classes /// Choose better roots for equivalence classes
void term_graph::pick_roots() { void term_graph::pick_roots() {
SASSERT(marks_are_clear());
for (term* t : m_terms) { for (term* t : m_terms) {
if (!t->is_marked() && t->is_root()) if (!t->is_marked() && t->is_root())
pick_root(*t); pick_root(*t);
@ -589,7 +598,7 @@ namespace qe {
// prefer a node that resembles current child, // prefer a node that resembles current child,
// otherwise, pick a root representative, if present. // otherwise, pick a root representative, if present.
if (m_term2app.find(ch->get_id(), e)) if (m_term2app.find(ch->get_id(), e))
kids.push_back(e); kids.push_back(e);
else if (m_root2rep.find(ch->get_root().get_id(), e)) else if (m_root2rep.find(ch->get_root().get_id(), e))
kids.push_back(e); kids.push_back(e);
else else

1
src/qe/qe_term_graph.h
View file

@ -75,6 +75,7 @@ namespace qe {
void pick_roots(); void pick_roots();
void reset_marks(); void reset_marks();
bool marks_are_clear();
expr* mk_app_core(expr* a); expr* mk_app_core(expr* a);
expr_ref mk_app(term const &t); expr_ref mk_app(term const &t);