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added try_factor

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2022-12-09 14:58:37 -08:00
parent 6e886114f9
commit c27bd0d650
2 changed files with 63 additions and 12 deletions
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71
src/math/polysat/saturation.cpp
View file

@ -34,12 +34,13 @@ namespace polysat {
void saturation::perform(pvar v, conflict& core) {
for (auto c : core)
if (perform(v, c, core))
return;
if (perform(v, c, core)) {
IF_VERBOSE(0, verbose_stream() << m_rule << " v" << v << " " << c << "\n");
return;
}
}
bool saturation::perform(pvar v, signed_constraint const& c, conflict& core) {
IF_VERBOSE(0, verbose_stream() << v << " " << c << " " << c.is_currently_true(s) << "\n");
if (!c->is_ule())
return false;
if (c.is_currently_true(s))
@ -223,6 +224,18 @@ namespace polysat {
return i.rhs() == y && i.lhs() == a * s.var(x) + b;
}
bool saturation::is_Y_l_AxB(pvar x, inequality const& i, pdd& y, pdd& a, pdd& b) {
y = i.lhs();
pdd aa = a, bb = b;
return i.rhs().degree(x) == 1 && (i.rhs().factor(x, 1, aa, bb), aa == a && bb == b);
}
bool saturation::verify_Y_l_AxB(pvar x, inequality const& i, pdd const& y, pdd const& a, pdd& b) {
return i.lhs() == y && i.rhs() == a * s.var(x) + b;
}
/**
* Match [x] a*x + b <= y, val(y) = 0
*/
@ -561,7 +574,7 @@ namespace polysat {
//
// NSB review: should we handle cases where k_val >= 2^{K-1}, but exploit that x*y = 0 iff -x*y = 0?
//
IF_VERBOSE(0, verbose_stream() << "mult-bounds2 " << Y << " " << axb_l_y.as_signed_constraint() << " " << u_l_k.as_signed_constraint() << " \n");
// IF_VERBOSE(0, verbose_stream() << "mult-bounds2 " << Y << " " << axb_l_y.as_signed_constraint() << " " << u_l_k.as_signed_constraint() << " \n");
rational bound = ceil(rational::power_of_two(m.power_of_2()) / k_val);
if (prop2(d, s.uge(Y, bound)))
return true;
@ -569,8 +582,8 @@ namespace polysat {
return true;
}
IF_VERBOSE(0, verbose_stream() << "mult-bounds1 " << a << " " << axb_l_y.as_signed_constraint() << " \n");
IF_VERBOSE(0, verbose_stream() << core << "\n");
// IF_VERBOSE(0, verbose_stream() << "mult-bounds1 " << a << " " << axb_l_y.as_signed_constraint() << " \n");
// IF_VERBOSE(0, verbose_stream() << core << "\n");
if (prop1(s.umul_ovfl(a, X)))
return true;
if (prop1(s.umul_ovfl(a, -X)))
@ -638,8 +651,6 @@ namespace polysat {
*/
bool saturation::try_parity(pvar x, conflict& core, inequality const& axb_l_y) {
set_rule("[x] a*x + b = 0 => (odd(a) & odd(x) <=> odd(b))");
IF_VERBOSE(0, verbose_stream() << "try parity " << axb_l_y.as_signed_constraint() << "\n");
auto& m = s.var2pdd(x);
unsigned N = m.power_of_2();
pdd y = m.zero();
@ -652,6 +663,8 @@ namespace polysat {
return false;
if (a.is_one() && (-b).is_var()) // y == x
return false;
if (a.is_one())
return false;
signed_constraint b_is_odd = s.odd(b);
signed_constraint a_is_odd = s.odd(a);
signed_constraint x_is_odd = s.odd(X);
@ -783,10 +796,44 @@ namespace polysat {
*/
bool saturation::try_factor_equality(pvar x, conflict& core, inequality const& a_l_b) {
// search for abx+p pattern in a_l_b.lhs()
// search for ax + r = 0 equality in core (or in search but maybe not needed)
// replace abx by -rb in patterns on either a_l_b.lhs() or a_l_b.rhs() or both if available to form new implied
// literal wtihout occurrence of x
auto& m = s.var2pdd(x);
unsigned N = m.power_of_2();
pdd y = m.zero();
pdd a = m.zero();
pdd b = m.zero();
pdd y2 = m.zero();
pdd a2 = m.zero();
pdd b2 = m.zero();
pdd X = s.var(x);
bool is_axb_l_y = is_AxB_l_Y(x, a_l_b, a, b, y);
bool is_y_l_axb = !is_axb_l_y && is_Y_l_AxB(x, a_l_b, y, a, b);
if (!is_axb_l_y && !is_y_l_axb)
return false;
if (a.is_val())
return false;
for (auto c : core) {
if (!c->is_ule())
continue;
auto i = inequality::from_ule(c);
if (i.is_strict())
continue;
if (!is_AxB_eq_0(x, i, a2, b2, y2))
continue;
if (a != a2) {
IF_VERBOSE(0, verbose_stream() << "misaligned coefficients " << a << " vs " << a2 << "\n");
continue; // punt on more general case for first iteration.
}
m_lemma.reset();
m_lemma.insert(~s.eq(y2));
m_lemma.insert(~c);
IF_VERBOSE(0, verbose_stream() << "factor equality " << a_l_b.as_signed_constraint() << "\n");
if (propagate(core, a_l_b, is_axb_l_y ? s.ule(b - b2, y) : s.ule(y, b - b2)))
return true;
}
return false;
}
/*

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

@ -79,6 +79,10 @@ namespace polysat {
bool is_AxB_l_Y(pvar x, inequality const& c, pdd& a, pdd& b, pdd& y);
bool verify_AxB_l_Y(pvar x, inequality const& c, pdd const& a, pdd const& b, pdd const& y);
// c := Y ~ Ax + B
bool is_Y_l_AxB(pvar x, inequality const& c, pdd& y, pdd& a, pdd& b);
bool verify_Y_l_AxB(pvar x, inequality const& c, pdd const& y, pdd const& a, pdd& b);
// c := Ax + B ~ Y, val(Y) = 0
bool is_AxB_eq_0(pvar x, inequality const& c, pdd& a, pdd& b, pdd& y);
bool verify_AxB_eq_0(pvar x, inequality const& c, pdd const& a, pdd const& b, pdd const& y);