mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-04-24 17:45:32 +00:00
Code Activity

fix todo on enforcing premises

Browse source 
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-09-22 12:26:45 -07:00
parent e5df395380
commit 3447d80310
4 changed files with 64 additions and 55 deletions
Download patch file Download diff file Expand all files Collapse all files

52
src/math/polysat/conflict.cpp
View file

@ -146,22 +146,35 @@ namespace polysat {
m_constraints.push_back(c);
}
void conflict::insert(signed_constraint c, vector<signed_constraint> premises) {
void conflict::insert(signed_constraint c, vector<signed_constraint> const& premises) {
insert(c);
m_saturation_premises.insert(c, std::move(premises)); // TODO: map doesn't have move-insertion, so this still copies the vector.
// NOTE: maybe we should skip intermediate steps and just collect the leaf premises for c?
clause_builder c_lemma(s);
for (auto premise : premises) {
LOG_H3("premise: " << premise);
keep(premise);
SASSERT(premise->has_bvar());
SASSERT(premise.bvalue(s) == l_true);
// otherwise the propagation doesn't make sense
c_lemma.push(~premise.blit());
}
c_lemma.push(c.blit());
clause_ref lemma = c_lemma.build();
cm().store(lemma.get(), s);
if (s.m_bvars.value(c.blit()) == l_undef)
s.assign_bool(s.level(*lemma), c.blit(), lemma.get(), nullptr);
}
void conflict::remove(signed_constraint c) {
SASSERT(!c->has_bvar() || std::count(m_constraints.begin(), m_constraints.end(), c) == 0);
unset_mark(c);
if (c->has_bvar()) {
SASSERT(std::count(m_constraints.begin(), m_constraints.end(), c) == 0);
remove_literal(c.blit());
}
if (c->has_bvar())
remove_literal(c.blit());
else
m_constraints.erase(c);
}
void conflict::replace(signed_constraint c_old, signed_constraint c_new, vector<signed_constraint> c_new_premises) {
void conflict::replace(signed_constraint c_old, signed_constraint c_new, vector<signed_constraint> const& c_new_premises) {
remove(c_old);
insert(c_new, c_new_premises);
}
@ -185,10 +198,8 @@ namespace polysat {
SASSERT(!contains_literal(~lit));
SASSERT(std::count(cl.begin(), cl.end(), ~lit) == 0);
remove_literal(lit);
unset_mark(m.lookup(lit));
remove_literal(lit);
unset_mark(m.lookup(lit));
for (sat::literal lit2 : cl)
if (lit2 != lit)
insert(m.lookup(~lit2));
@ -205,25 +216,6 @@ namespace polysat {
insert(c);
}
LOG_H3("keeping: " << c);
// NOTE: maybe we should skip intermediate steps and just collect the leaf premises for c?
auto it = m_saturation_premises.find_iterator(c);
if (it == m_saturation_premises.end())
return;
auto& premises = it->m_value;
clause_builder c_lemma(s);
for (auto premise : premises) {
LOG_H3("premise: " << premise);
keep(premise);
SASSERT(premise->has_bvar());
SASSERT(premise.is_currently_true(s) || premise.bvalue(s) == l_true);
// otherwise the propagation doesn't make sense
c_lemma.push(~premise.blit());
}
c_lemma.push(c.blit());
clause_ref lemma = c_lemma.build();
cm().store(lemma.get(), s);
if (s.m_bvars.value(c.blit()) == l_undef)
s.assign_bool(s.level(*lemma), c.blit(), lemma.get(), nullptr);
}
clause_builder conflict::build_lemma() {

4
src/math/polysat/conflict.h
View file

@ -86,9 +86,9 @@ namespace polysat {
void set(clause const& cl);
void insert(signed_constraint c);
void insert(signed_constraint c, vector<signed_constraint> premises);
void insert(signed_constraint c, vector<signed_constraint> const& premises);
void remove(signed_constraint c);
void replace(signed_constraint c_old, signed_constraint c_new, vector<signed_constraint> c_new_premises);
void replace(signed_constraint c_old, signed_constraint c_new, vector<signed_constraint> const& c_new_premises);
void keep(signed_constraint c);

61
src/math/polysat/explain.cpp
View file

@ -46,48 +46,65 @@ namespace polysat {
// c2 ... constraint that is currently false
// Try to replace it with a new false constraint (derived from superposition with a true constraint)
signed_constraint ex_polynomial_superposition::find_replacement(signed_constraint c2, pvar v, conflict& core) {
lbool ex_polynomial_superposition::find_replacement(signed_constraint c2, pvar v, conflict& core) {
vector<signed_constraint> premises;
for (auto c1 : core) {
if (!is_positive_equality_over(v, c1))
continue;
if (!c1.is_currently_true(s()))
continue;
signed_constraint c = resolve1(v, c1, c2);
if (!c)
continue;
vector<signed_constraint> premises;
premises.push_back(c1);
premises.push_back(c2);
core.replace(c2, c, std::move(premises));
return c;
if (!c->has_bvar())
s().m_constraints.ensure_bvar(c.get());
switch (c.bvalue(s())) {
case l_false:
// new conflict state based on propagation and theory conflict
core.reset();
core.insert(c1);
core.insert(c2);
core.insert(~c);
return l_true;
case l_undef:
// Ensure that c is assigned and justified
premises.push_back(c1);
premises.push_back(c2);
core.replace(c2, c, premises);
SASSERT(l_true == c.bvalue(s()));
SASSERT(c.is_currently_false(s()));
break;
default:
break;
}
// NOTE: more variables than just 'v' might have been removed here (see polysat::test_p3).
// c alone (+ variables) is now enough to represent the conflict.
core.reset();
core.set(c);
return c->contains_var(v) ? l_undef : l_true;
}
return {};
return l_false;
}
// TODO(later): check superposition into disequality again (see notes)
// true = done, false = abort, undef = continue
// TODO: can try multiple replacements at once; then the c2 loop needs to be done only once... (requires some reorganization for storing the premises)
lbool ex_polynomial_superposition::try_explain1(pvar v, conflict& core) {
for (auto c2 : core) {
if (!is_positive_equality_over(v, c2))
continue;
if (!c2.is_currently_false(s()))
continue;
// TODO: can try multiple replacements at once; then the c2 loop needs to be done only once... (requires some reorganization for storing the premises)
signed_constraint c = find_replacement(c2, v, core);
if (!c)
continue;
if (c->contains_var(v))
switch (find_replacement(c2, v, core)) {
case l_undef:
return l_undef;
if (!c->has_bvar() || l_undef == c.bvalue(s()))
core.keep(c); // adds propagation of c to the search stack
// NOTE: more variables than just 'v' might have been removed here (see polysat::test_p3).
// c alone (+ variables) is now enough to represent the conflict.
core.reset();
core.set(c);
return l_true;
case l_true:
return l_true;
case l_false:
continue;
}
}
return l_false;
}

2
src/math/polysat/explain.h
View file

@ -36,7 +36,7 @@ namespace polysat {
private:
bool is_positive_equality_over(pvar v, signed_constraint const& c);
signed_constraint resolve1(pvar v, signed_constraint c1, signed_constraint c2);
signed_constraint find_replacement(signed_constraint c2, pvar v, conflict& core);
lbool find_replacement(signed_constraint c2, pvar v, conflict& core);
void reduce_by(pvar v, conflict& core);
bool reduce_by(pvar, signed_constraint c, conflict& core);
lbool try_explain1(pvar v, conflict& core);