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initial overflow test

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-12-09 14:39:00 -08:00
parent 99e2247ccb
commit a4fc63c542
6 changed files with 47 additions and 8 deletions
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20
src/math/polysat/mul_ovfl_constraint.cpp
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@ -18,7 +18,6 @@ namespace polysat {
mul_ovfl_constraint::mul_ovfl_constraint(constraint_manager& m, pdd const& p, pdd const& q):
constraint(m, ckind_t::mul_ovfl_t), m_p(p), m_q(q) {
simplify();
m_vars.append(m_p.free_vars());
for (auto v : m_q.free_vars())
@ -33,6 +32,8 @@ namespace polysat {
m_p = 0;
return;
}
if (m_p.index() > m_q.index())
std::swap(m_p, m_q);
}
std::ostream& mul_ovfl_constraint::display(std::ostream& out, lbool status) const {
@ -104,8 +105,6 @@ namespace polysat {
* TODO optimizations:
* if p is constant, q variable, update viable for q
*
* Use bounds on variables in p instead of current assignment as premise.
* This is a more general lemma
*/
bool mul_ovfl_constraint::narrow_bound(solver& s, bool is_positive,
pdd const& p0, pdd const& q0, pdd const& p, pdd const& q) {
@ -118,22 +117,31 @@ namespace polysat {
// p * q >= max + 1 <=> q >= (max + 1)/p <=> q >= ceil((max+1)/p)
auto bound = ceil((max + 1) / p.val());
//
// the clause that explains bound <= q or bound > q
//
// Ovfl(p, q) & p <= p.val() => q >= bound
// ~Ovfl(p, q) & p >= p.val() => q < bound
// ~Ovfl(p, q) & p >= p.val() => q < bound
//
signed_constraint sc(this, is_positive);
signed_constraint premise = is_positive ? s.ule(p0, p.val()) : s.ule(p.val(), p0);
signed_constraint conseq = is_positive ? s.ule(bound, q0) : s.ult(q0, bound);
SASSERT(premise.is_currently_false(s));
//std::cout << premise << "\n";
//std::cout << sc << "\n";
//std::cout << conseq << "\n";
//std::cout << "Already true " << conseq.is_currently_true(s) << "\n";
SASSERT(premise.is_currently_true(s));
clause_builder cb(s);
cb.push_new(~sc);
cb.push_new(~premise);
cb.push_new(conseq);
clause_ref just = cb.build();
s.assign_propagate(conseq.blit(), *just);
s.add_lemma(*just);
s.propagate();
SASSERT(s.m_bvars.is_true(conseq.blit()));
return true;
}