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Variant of variable elimination

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This commit is contained in:
Clemens Eisenhofer 2023-01-02 20:05:13 +01:00
parent 1c7ac12af8
commit 0301686856
3 changed files with 91 additions and 27 deletions
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37
src/math/polysat/saturation.cpp
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@ -870,19 +870,24 @@ namespace polysat {
if (s.try_eval(p, val))
return val == 0 ? N : val.trailing_zeros();
if (!p.is_var() && p.is_monomial()) {
// it's just a product => sum them up
dd::pdd_monomial monomial = *p.begin();
unsigned parity_sum = monomial.coeff.trailing_zeros();
for (pvar c : monomial.vars)
parity_sum += min_parity(m.mk_var(c));
return std::min(N, parity_sum);
unsigned min = 0;
if (!p.is_var()) {
// parity of a product => sum of parities
// parity of sum => minimum of monomial's minimal parities
min = UINT32_MAX;
for (const auto& monomial : p) {
unsigned parity_sum = monomial.coeff.trailing_zeros();
for (pvar c : monomial.vars)
parity_sum += min_parity(m.mk_var(c));
min = std::min(min, parity_sum);
}
}
SASSERT(min <= N);
for (unsigned j = N; j > 0; --j)
for (unsigned j = N; j > min; --j)
if (is_forced_true(s.parity_at_least(p, j)))
return j;
return 0;
return min;
}
unsigned saturation::max_parity(pdd const& p) {
@ -892,19 +897,21 @@ namespace polysat {
if (s.try_eval(p, val))
return val == 0 ? N : val.trailing_zeros();
unsigned max = N;
if (!p.is_var() && p.is_monomial()) {
// it's just a product => sum them up
// the case of a sum is harder as the lower bound (because of carry bits)
// ==> restricted for now to monomials
dd::pdd_monomial monomial = *p.begin();
unsigned parity_sum = monomial.coeff.trailing_zeros();
max = monomial.coeff.trailing_zeros();
for (pvar c : monomial.vars)
parity_sum += max_parity(m.mk_var(c));
return std::min(N, parity_sum);
max += max_parity(m.mk_var(c));
}
for (unsigned j = 0; j < N; ++j)
for (unsigned j = 0; j < max; ++j)
if (is_forced_true(s.parity_at_most(p, j)))
return j;
return N;
return max;
}
bool saturation::try_parity(pvar x, conflict& core, inequality const& axb_l_y) {
@ -1220,7 +1227,7 @@ namespace polysat {
m_lemma.reset();
m_lemma.insert(~c);
m_lemma.insert_eval(~s.eq(y));
for (auto& sc_lhs : side_condition_lhs) // TODO: Do we really need the path as a side-condition in case of parity elimination?
for (auto& sc_lhs : side_condition_lhs) // the "path to get the parities"
m_lemma.insert(sc_lhs);
for (auto& sc_rhs : side_condition_rhs)
m_lemma.insert(sc_rhs);