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Tweak ule simplifications

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This commit is contained in:
Jakob Rath 2023-02-22 16:36:10 +01:00
parent 14b2c38e7f
commit 6eb0d91504
1 changed files with 30 additions and 11 deletions
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41
src/math/polysat/ule_constraint.cpp
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@ -75,7 +75,10 @@ Useful lemmas:
namespace { namespace {
using namespace polysat; using namespace polysat;
// Simplify lhs <= rhs // Simplify lhs <= rhs.
//
// NOTE: the result should not depend on the initial value of is_positive;
// the purpose of is_positive is to allow flipping the sign as part of a rewrite rule.
void simplify_impl(bool& is_positive, pdd& lhs, pdd& rhs) { void simplify_impl(bool& is_positive, pdd& lhs, pdd& rhs) {
// 0 <= p --> 0 <= 0 // 0 <= p --> 0 <= 0
if (lhs.is_zero()) { if (lhs.is_zero()) {
@ -102,25 +105,40 @@ namespace {
} }
#if 0 #if 0
// !(k <= p) -> p <= k - 1 // TODO: maybe enable this later to make some constraints more "readable"
// p - k <= -k - 1 --> k <= p
if (!is_positive && lhs.is_val() && lhs.val() > 0) { if (rhs.is_val() && !rhs.is_zero() && lhs.offset() == (rhs + 1).val()) {
pdd k = lhs; // LOG("Simplifying " << lhs << " <= " << rhs);
lhs = rhs; std::abort();
rhs = k - 1; pdd k = -(rhs + 1);
is_positive = true; rhs = lhs + k;
lhs = k;
// LOG(" into " << lhs << " <= " << rhs);
} }
#endif #endif
// -1 <= p --> p + 1 <= 0 // -1 <= p --> p + 1 <= 0
// 1 <= p --> p - 1 <= -2 (--> p > 0 later) if (lhs.is_max()) {
lhs = rhs + 1;
rhs = 0;
}
// 1 <= p --> p > 0
if (lhs.is_one()) {
lhs = rhs;
rhs = 0;
is_positive = !is_positive;
}
#if 0
// TODO: enabling this rule leads to unsoundness in 1041-minimized (but the rule itself is correct)
// k <= p --> p - k <= - k - 1 // k <= p --> p - k <= - k - 1
if (lhs.is_val()) { if (lhs.is_val()) {
pdd k = lhs; pdd k = lhs;
lhs = rhs - k; lhs = rhs - k;
rhs = - k - 1; rhs = - k - 1;
} }
// NSB: why this? #endif
// p + 1 <= p --> p + 1 <= 0 // p + 1 <= p --> p + 1 <= 0
// p <= p - 1 --> p <= 0 // p <= p - 1 --> p <= 0
@ -164,7 +182,8 @@ namespace {
// p > -2 --> p + 1 <= 0 // p > -2 --> p + 1 <= 0
// p <= -2 --> p + 1 > 0 // p <= -2 --> p + 1 > 0
if (rhs.is_val() && (rhs + 2).is_zero()) { if (rhs.is_val() && !rhs.is_zero() && (rhs + 2).is_zero()) {
// Note: rhs.is_zero() iff rhs.manager().power_of_2() == 1 (the rewrite is not wrong for M=2, but useless)
lhs = lhs + 1; lhs = lhs + 1;
rhs = 0; rhs = 0;
is_positive = !is_positive; is_positive = !is_positive;