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Merge branch 'polysat' of https://github.com/z3prover/z3 into polysat

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This commit is contained in:
Nikolaj Bjorner 2022-12-29 16:55:56 -08:00
commit ed76da1458
7 changed files with 235 additions and 65 deletions
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71
src/math/polysat/saturation.cpp
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@ -30,7 +30,7 @@ TODO: when we check that 'x' is "unary":
namespace polysat {
saturation::saturation(solver& s) : s(s), m_lemma(s) {}
saturation::saturation(solver& s) : s(s), m_lemma(s), m_parity_tracker(s) {}
void saturation::log_lemma(pvar v, conflict& core) {
IF_VERBOSE(1, auto const& cl = core.lemmas().back();
@ -880,7 +880,7 @@ namespace polysat {
}
for (unsigned j = N; j > 0; --j)
if (is_forced_true(s.parity(p, j)))
if (is_forced_true(s.parity_at_least(p, j)))
return j;
return 0;
}
@ -971,7 +971,7 @@ namespace polysat {
auto at_least = [&](pdd const& p, unsigned k) {
VERIFY(k != 0);
return s.parity(p, k);
return s.parity_at_least(p, k);
};
@ -1020,7 +1020,7 @@ namespace polysat {
m_lemma.reset();
m_lemma.insert_eval(~s.eq(y));
m_lemma.insert_eval(~s.eq(b));
if (propagate(x, core, axb_l_y, ~s.parity(X, N - k)))
if (propagate(x, core, axb_l_y, ~s.parity_at_least(X, N - k)))
return true;
// TODO parity on a (without leading coefficient?)
}
@ -1135,7 +1135,7 @@ namespace polysat {
lbool saturation::get_multiple(const pdd& p1, const pdd& p2, pdd& out) {
LOG("Check if " << p2 << " can be multiplied with something to get " << p1);
if (p1.is_zero()) {
if (p1.is_zero()) { // TODO: use the evaluated parity (max_parity) instead?
out = p1.manager().zero();
return l_true;
}
@ -1202,40 +1202,8 @@ namespace polysat {
if (!is_AxB_eq_0(x, a_l_b, a, b, y)) // TODO: Is the restriction to linear "x" too restrictive?
return false;
bool is_invertible = a.is_val() && a.val().is_odd();
if (is_invertible) {
rational a_inv;
VERIFY(a.val().mult_inverse(m.power_of_2(), a_inv));
b = -b * a_inv;
}
bool change = false;
bool prop = false;
auto replace = [&](pdd p) {
unsigned p_degree = p.degree(x);
if (p_degree == 0)
return p;
if (is_invertible) {
change = true;
// this works as well if the degree of "p" is not 1: 3 x = a (mod 4) & x^2 <= b => (3a)^2 <= b
return p.subst_pdd(x, b);
}
if (p_degree != 1)
return p; // TODO: Maybe fallback to brute-force
p.factor(x, 1, a1, b1);
lbool is_multiple = get_multiple(a1, a, mul_fac);
if (is_multiple == l_false)
return p; // there is no chance to invert
if (is_multiple == l_true) {
change = true;
return b1 - b * mul_fac;
}
// We don't know whether it will work. Brute-force the parity
// TODO: Brute force goes here
return p;
};
for (auto c : core) {
change = false;
@ -1243,27 +1211,38 @@ namespace polysat {
continue;
LOG("Trying to eliminate v" << x << " in " << c << " by using equation " << a_l_b.as_signed_constraint());
if (c->is_ule()) {
// If both are equalities this boils down to polynomial superposition => Might generate the same lemma twice
auto const& ule = c->to_ule();
auto p = replace(ule.lhs());
auto q = replace(ule.rhs());
if (!change)
continue;
auto [lhs_new, changed_lhs, side_condition_lhs] = m_parity_tracker.eliminate_variable(*this, x, a, b, ule.lhs());
auto [rhs_new, changed_rhs, side_condition_rhs] = m_parity_tracker.eliminate_variable(*this, x, a, b, ule.rhs());
if (!changed_lhs && !changed_rhs)
continue; // nothing changed - no reason for propagating lemmas
m_lemma.reset();
m_lemma.insert(~c);
m_lemma.insert_eval(~s.eq(y));
if (propagate(x, core, a_l_b, c.is_positive() ? s.ule(p, q) : ~s.ule(p, q)))
for (auto& sc_lhs : side_condition_lhs) // TODO: Do we really need the path as a side-condition in case of parity elimination?
m_lemma.insert(sc_lhs);
for (auto& sc_rhs : side_condition_rhs)
m_lemma.insert(sc_rhs);
if (propagate(x, core, a_l_b, c.is_positive() ? s.ule(lhs_new, rhs_new) : ~s.ule(lhs_new, rhs_new)))
prop = true;
}
else if (c->is_umul_ovfl()) {
auto const& ovf = c->to_umul_ovfl();
auto p = replace(ovf.p());
auto q = replace(ovf.q());
if (!change)
auto [lhs_new, changed_lhs, side_condition_lhs] = m_parity_tracker.eliminate_variable(*this, x, a, b, ovf.p());
auto [rhs_new, changed_rhs, side_condition_rhs] = m_parity_tracker.eliminate_variable(*this, x, a, b, ovf.q());
if (!changed_lhs && !changed_rhs)
continue;
m_lemma.reset();
m_lemma.insert(~c);
m_lemma.insert_eval(~s.eq(y));
if (propagate(x, core, a_l_b, c.is_positive() ? s.umul_ovfl(p, q) : ~s.umul_ovfl(p, q)))
for (auto& sc_lhs : side_condition_lhs)
m_lemma.insert(sc_lhs);
for (auto& sc_rhs : side_condition_rhs)
m_lemma.insert(sc_rhs);
if (propagate(x, core, a_l_b, c.is_positive() ? s.umul_ovfl(lhs_new, rhs_new) : ~s.umul_ovfl(lhs_new, rhs_new)))
prop = true;
}
}