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finish sketch of special case interval propagation

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-09-09 12:23:03 +02:00
parent 6e9e8999dc
commit ed60cdc403
2 changed files with 50 additions and 7 deletions
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2
src/math/polysat/boolean.h
View file

@ -28,7 +28,7 @@ namespace polysat {
svector<clause*> m_lemma;
unsigned_vector m_marks;
unsigned m_clock { 0 };
unsigned m_clock = 0;
public:
// allocated size (not the number of active variables)

55
src/math/polysat/saturation.cpp
View file

@ -161,7 +161,7 @@ namespace polysat {
return true;
}
// special case viable sets.
// special case viable sets used by variables.
bool inf_saturate::push_omega_viable(conflict_core& core, clause_builder& reason, unsigned level, pdd const& px, pdd const& py) {
if (!px.is_var() || !py.is_var())
return false;
@ -171,7 +171,8 @@ namespace polysat {
rational y_max = s().m_viable.max_viable(y);
auto& pddm = px.manager();
unsigned bit_size = pddm.power_of_2();
if (x_max * y_max < rational::power_of_two(bit_size)) {
rational bound = rational::power_of_two(bit_size);
if (x_max * y_max < bound) {
// max values don't overflow, we can justify no-overflow using cjust for x, y
for (auto c : s().m_cjust[x])
reason.push(c);
@ -183,13 +184,55 @@ namespace polysat {
rational x_val = s().get_value(x);
rational y_val = s().get_value(y);
if (x_val * y_val >= rational::power_of_two(bit_size))
if (x_val * y_val >= bound)
return false;
// TODO: try bisection approach to find values between x_val and y_val and x_max, y_max
// find x_mid, y_mid that doesn't overflow.
rational x_lo = x_val, x_hi = x_max, y_lo = y_val, y_hi = y_max;
rational two(2);
while (x_lo < x_hi || y_lo < y_hi) {
rational x_mid = div(x_hi + x_lo, two);
rational y_mid = div(y_hi + y_lo, two);
if (x_mid * y_mid >= bound)
x_hi = x_mid - 1, y_hi = y_mid - 1;
else
x_lo = x_mid, y_lo = y_mid;
}
SASSERT(x_hi == x_lo && y_hi == y_lo);
SASSERT(x_lo * y_lo < bound);
SASSERT((x_lo + 1) * (y_lo + 1) >= bound);
if ((x_lo + 1) * y_lo < bound) {
x_hi = x_max;
while (x_lo < x_hi) {
rational x_mid = div(x_hi + x_lo, two);
if (x_mid * y_lo >= bound)
x_hi = x_mid - 1;
else
x_lo = x_mid;
}
}
else if (x_lo * (y_lo + 1) < bound) {
y_hi = y_max;
while (y_lo < y_hi) {
rational y_mid = div(y_hi + y_lo, two);
if (y_mid * x_lo >= bound)
y_hi = y_mid - 1;
else
y_lo = y_mid;
}
}
SASSERT(x_lo * y_lo < bound);
SASSERT((x_lo + 1) * y_lo >= bound);
SASSERT(x_lo * (y_lo + 1) >= bound);
return false;
// inequalities are justified by current assignments to px, py
// conflict resolution should be able to pick up this as a valid justification.
// or we resort to the same extension as in the original mul_overflow code
// where we add explicit equality propagations from the current assignment.
auto c1 = s().m_constraints.ule(level, px, pddm.mk_val(x_lo));
auto c2 = s().m_constraints.ule(level, py, pddm.mk_val(y_lo));
reason.push(c1);
reason.push(c2);
return true;
}
/*