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add parity constraint for disequality

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2022-12-12 19:40:19 -08:00
parent 479e0e58ea
commit a5f12e9d57
3 changed files with 46 additions and 2 deletions
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2
src/math/polysat/conflict.cpp
View file

@ -298,7 +298,7 @@ namespace polysat {
void conflict::insert_vars(signed_constraint c) {
for (pvar v : c->vars())
if (s.is_assigned(v))
if (s.is_assigned(v))
m_vars.insert(v);
}

43
src/math/polysat/saturation.cpp
View file

@ -35,7 +35,10 @@ namespace polysat {
void saturation::perform(pvar v, conflict& core) {
for (auto c : core)
if (perform(v, c, core)) {
IF_VERBOSE(0, verbose_stream() << m_rule << " v" << v << " " << c << "\n");
IF_VERBOSE(0, auto const& cl = core.lemmas().back();
verbose_stream() << m_rule << " v" << v << " ";
for (auto lit : *cl) verbose_stream() << s.lit2cnstr(lit) << " ";
verbose_stream() << "\n");
return;
}
}
@ -50,6 +53,8 @@ namespace polysat {
return true;
if (try_parity(v, core, i))
return true;
if (try_parity_diseq(v, core, i))
return true;
if (try_factor_equality(v, core, i))
return true;
if (try_ugt_x(v, core, i))
@ -251,6 +256,16 @@ namespace polysat {
return y.is_val() && y.val() == 0 && i.rhs() == y && i.lhs() == a * s.var(x) + b;
}
bool saturation::is_AxB_diseq_0(pvar x, inequality const& i, pdd& a, pdd& b, pdd& y) {
if (!i.is_strict())
return false;
y = i.lhs();
rational y_val;
if (!s.try_eval(y, y_val) || y_val != 0)
return false;
return i.rhs().degree(x) == 1 && (i.rhs().factor(x, 1, a, b), true);
}
/**
* Match [coeff*x] coeff*x*Y where x is a variable
*/
@ -755,6 +770,32 @@ namespace polysat {
return false;
}
/**
* 2^{K-1}*x*y != 0 => odd(x) & odd(y)
* 2^k*x != 0 => parity(x) < K - k
* 2^k*x*y != 0 => parity(x) + parity(y) < K - k
*/
bool saturation::try_parity_diseq(pvar x, conflict& core, inequality const& axb_l_y) {
set_rule("[x] 2^k*x*y != 0 => parity(x) + parity(y) < K - k");
auto& m = s.var2pdd(x);
unsigned N = m.power_of_2();
pdd y = m.zero();
pdd a = y, b = y, X = y;
if (!is_AxB_diseq_0(x, axb_l_y, a, b, y))
return false;
if (!is_forced_eq(b, 0))
return false;
auto coeff = a.leading_coefficient();
if (coeff.is_odd())
return false;
SASSERT(coeff != 0);
unsigned k = coeff.trailing_zeros();
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~s.eq(b));
return propagate(core, axb_l_y, ~s.parity(X, N - k));
}
/**
* a*x = 0 => a = 0 or even(x)
* a*x = 0 => a = 0 or x = 0 or even(a)

3
src/math/polysat/saturation.h
View file

@ -47,6 +47,7 @@ namespace polysat {
bool try_ugt_z(pvar z, conflict& core, inequality const& x_l_z0, inequality const& yz_l_xz, pdd const& y, pdd const& x);
bool try_parity(pvar x, conflict& core, inequality const& axb_l_y);
bool try_parity_diseq(pvar x, conflict& core, inequality const& axb_l_y);
bool try_mul_bounds(pvar x, conflict& core, inequality const& axb_l_y);
bool try_factor_equality(pvar x, conflict& core, inequality const& a_l_b);
bool try_mul_eq_1(pvar x, conflict& core, inequality const& axb_l_y);
@ -87,6 +88,8 @@ namespace polysat {
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);
// c := Ax + B != Y, val(Y) = 0
bool is_AxB_diseq_0(pvar x, inequality const& c, pdd& a, pdd& b, pdd& y);
// c := Y*X ~ z*X
bool is_YX_l_zX(pvar z, inequality const& c, pdd& x, pdd& y);