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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-06-20 12:38:20 -07:00
parent 4fad0385de
commit 19099244c4
5 changed files with 49 additions and 14 deletions
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27
src/math/polysat/eq_constraint.cpp
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@ -59,20 +59,29 @@ namespace polysat {
if (q.is_unilinear()) {
// a*x + b == 0
pvar v = q.var();
s.push_cjust(v, this);
rational a = q.hi().val();
rational b = q.lo().val();
bddv const& x = s.var2bits(v).var();
bddv lhs = a * x + b;
rational zero = rational::zero();
bdd xs = is_positive() ? (lhs == zero) : (lhs != zero);
s.push_cjust(v, this);
s.intersect_viable(v, xs);
rational val;
if (s.find_viable(v, val) == dd::find_t::singleton) {
s.propagate(v, val, *this);
if (b == 0 && a.is_odd()) {
// hacky test optimizing special case.
// general case is compute inverse(a)*-b for equality 2^k*a*x + b == 0
// then constrain x.
//
s.intersect_viable(v, is_positive() ? x.all0() : !x.all0());
}
else {
IF_VERBOSE(10, verbose_stream() << a << "*x + " << b << "\n");
bddv lhs = a * x + b;
bdd xs = is_positive() ? lhs.all0() : !lhs.all0();
s.intersect_viable(v, xs);
}
rational val;
if (s.find_viable(v, val) == dd::find_t::singleton)
s.propagate(v, val, *this);
return;
}