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sketch parity generalization

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2022-12-07 20:04:58 -08:00
parent 55d691e16e
commit 437f826e8b
4 changed files with 118 additions and 17 deletions
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82
src/math/polysat/saturation.cpp
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@ -633,6 +633,7 @@ 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))");
auto& m = s.var2pdd(x);
unsigned N = m.power_of_2();
pdd y = m.zero();
pdd a = m.zero();
pdd b = m.zero();
@ -653,29 +654,78 @@ namespace polysat {
LOG("a_is_odd: " << lit_pp(s, a_is_odd));
LOG("x_is_odd: " << lit_pp(s, x_is_odd));
#endif
if (!b_is_odd.is_currently_true(s)) {
if (!a_is_odd.is_currently_true(s))
return false;
if (!x_is_odd.is_currently_true(s))
return false;
if (a_is_odd.is_currently_true(s) &&
x_is_odd.is_currently_true(s)) {
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~a_is_odd);
m_lemma.insert_eval(~x_is_odd);
if (propagate(core, axb_l_y, b_is_odd))
return true;
return false;
}
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~b_is_odd);
if (propagate(core, axb_l_y, a_is_odd))
return true;
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~b_is_odd);
if (propagate(core, axb_l_y, x_is_odd))
return true;
#if 0
// TODO - enable this code and test
// a is divisibly by 4,
// max divisor of x is k
// -> b has parity k + 4
if ((~a_is_odd).is_currently_true(s) ||
(~x_is_odd).is_currently_true(s)) {
unsigned a_parity = 0;
unsigned x_parity = 0;
while (a_parity <= N && s.parity(a, a_parity+1).is_currently_true(s))
++a_parity;
while (x_parity <= N && s.parity(X, x_parity+1).is_currently_true(s))
++x_parity;
SASSERT(a_parity > 0 || x_parity > 0);
unsigned b_parity = std::min(N + 1, a_parity + x_parity);
if (a_parity > 0)
m_lemma.insert_eval(~s.parity(a, a_parity));
if (x_parity > 0)
m_lemma.insert_eval(~s.parity(X, x_parity));
if (propagate(core, axb_l_y, s.parity(b, b_parity)))
return true;
}
#endif
if (b_is_odd.is_currently_true(s)) {
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~b_is_odd);
if (propagate(core, axb_l_y, a_is_odd))
return true;
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~b_is_odd);
if (propagate(core, axb_l_y, x_is_odd))
return true;
}
#if 0
//
// if b has at least b_parity, then a*x has at least b_parity
// establish lower bound on parity of b
//
if ((~b_is_odd).is_currently_true(s) && !is_forced_eq(b, 0)) {
unsigned b_parity = 1;
while (b_parity <= N && s.parity(b, b_parity+1).is_currently_true(s))
++b_parity;
SASSERT(b_parity <= N);
// TODO:
// something like this (but fixed)
for (unsigned i = 0; i <= b_parity; ++i) {
if (s.parity(a, b_parity - i).is_currently_false(s)) {
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~s.parity(b, b_parity));
m_lemma.insert_eval(s.parity(a, b_parity - i));
if (propagate(core, axb_l_y, s.parity(x, i)))
return true;
}
}
}
#endif
return false;
}