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Remove unsound bvshl lemma

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This commit is contained in:
Jakob Rath 2023-03-05 15:38:07 +01:00
parent 9ed6bc66ce
commit 666c937b06
1 changed files with 9 additions and 15 deletions
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24
src/math/polysat/op_constraint.cpp
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@ -319,11 +319,10 @@ namespace polysat {
/**
* Enforce axioms for constraint: r == p << q
*
* q >= K -> r = 0
* q >= N -> r = 0
* q >= k -> r = 0 \/ r >= 2^k
* q >= k -> r[i] = 0 for i < k
* q = k -> r[i+k] = p[i] for 0 <= i < K - k
* r != 0 -> r >= p
* q = k -> r[i+k] = p[i] for 0 <= i < N - k
* q = 0 -> r = p
*/
clause_ref op_constraint::lemma_shl(solver& s, assignment const& a) {
@ -331,30 +330,25 @@ namespace polysat {
auto const pv = a.apply_to(p());
auto const qv = a.apply_to(q());
auto const rv = a.apply_to(r());
unsigned const K = m.power_of_2();
unsigned const N = m.power_of_2();
signed_constraint const shl(this, true);
if (pv.is_val() && !pv.is_zero() && !pv.is_one() && rv.is_val() && !rv.is_zero() && rv.val() < pv.val())
// r != 0 -> r >= p
// r = 0 \/ r >= p (equivalent)
// r-1 >= p-1 (equivalent unit constraint to better support narrowing)
return s.mk_clause(~shl, s.ule(p() - 1, r() - 1), true);
else if (qv.is_val() && qv.val() >= K && rv.is_val() && !rv.is_zero())
// q >= K -> r = 0
return s.mk_clause(~shl, ~s.ule(K, q()), s.eq(r()), true);
if (qv.is_val() && qv.val() >= N && rv.is_val() && !rv.is_zero())
// q >= N -> r = 0
return s.mk_clause(~shl, ~s.ule(N, q()), s.eq(r()), true);
else if (qv.is_zero() && pv.is_val() && rv.is_val() && rv != pv)
// q = 0 -> r = p
return s.mk_clause(~shl, ~s.eq(q()), s.eq(r(), p()), true);
else if (qv.is_val() && !qv.is_zero() && qv.val() < K && rv.is_val() &&
else if (qv.is_val() && !qv.is_zero() && qv.val() < N && rv.is_val() &&
!rv.is_zero() && rv.val() < rational::power_of_two(qv.val().get_unsigned()))
// q >= k -> r = 0 \/ r >= 2^k (intuitive version)
// q >= k -> r - 1 >= 2^k - 1 (equivalent unit constraint to better support narrowing)
return s.mk_clause(~shl, ~s.ule(qv.val(), q()), s.ule(rational::power_of_two(qv.val().get_unsigned()) - 1, r() - 1), true);
else if (pv.is_val() && rv.is_val() && qv.is_val() && !qv.is_zero()) {
unsigned k = qv.val().get_unsigned();
// q = k -> r[i+k] = p[i] for 0 <= i < K - k
for (unsigned i = 0; i < K - k; ++i) {
// q = k -> r[i+k] = p[i] for 0 <= i < N - k
for (unsigned i = 0; i < N - k; ++i) {
if (rv.val().get_bit(i + k) && !pv.val().get_bit(i)) {
return s.mk_clause(~shl, ~s.eq(q(), k), ~s.bit(r(), i + k), s.bit(p(), i), true);
}