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import equality superposition

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This commit is contained in:
Nikolaj Bjorner 2023-12-31 15:40:04 -08:00
parent b25451bd87
commit 7dd37a748d
2 changed files with 41 additions and 0 deletions
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38
src/sat/smt/polysat/saturation.cpp
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@ -66,6 +66,8 @@ namespace polysat {
try_ugt_y(v, i);
if (!c.inconsistent())
try_ugt_z(v, i);
if (!c.inconsistent())
try_eq_resolve(v, i);
}
void saturation::add_clause(char const* name, clause const& cs, bool is_redundant) {
@ -202,4 +204,40 @@ namespace polysat {
}
}
void saturation::try_eq_resolve(pvar v, inequality const& i) {
if (!i.rhs().is_zero() || i.is_strict())
return;
for (auto id : constraint_iterator(c, [&](auto const& sc) { return sc.is_ule() && !sc.sign() && sc.rhs().is_zero(); })) {
auto sc = c.get_constraint(id);
if (!sc.unfold_vars().contains(v))
continue;
auto j = inequality::from_ule(sc);
SASSERT(!j.is_strict());
try_eq_resolve(v, i, j);
}
}
void saturation::try_eq_resolve(pvar v, inequality const& i, inequality const& j) {
// i is true, j is false, both their rhs are 0.
SASSERT(i.rhs().is_zero() && j.rhs().is_zero() && !i.is_strict() && !j.is_strict());
pdd a = i.lhs();
pdd b = j.lhs();
unsigned degree_a = a.degree();
unsigned degree_b = b.degree();
pdd r = a;
if (!a.resolve(v, b, r) && !b.resolve(v, a, r))
return;
unsigned degree_r = r.degree();
if (degree_a < degree_r && degree_b < degree_r)
return;
// Only keep result if the degree in c2 was reduced.
// (this condition might be too strict, but we use it for now to prevent looping)
if (b.degree(v) <= r.degree(v))
return;
if (a.degree(v) <= r.degree(v))
return;
add_clause("ax + b = 0 & cx + d = 0 ==> cb - da = 0", { i.dep(), j.dep(), C.eq(r) }, true);
}
}

3
src/sat/smt/polysat/saturation.h
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@ -71,6 +71,9 @@ namespace polysat {
void resolve(pvar v, inequality const& i);
bool resolve(pvar v, constraint_id cid);
void try_eq_resolve(pvar v, inequality const& i, inequality const& j);
void try_eq_resolve(pvar v, inequality const& i);
public:
saturation(core& c);
lbool operator()();