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Update quot_rem axioms

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Jakob Rath 2022-01-18 10:43:12 +01:00
parent e005838129
commit 175b348948
1 changed files with 17 additions and 7 deletions
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24
src/math/polysat/solver.cpp
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@ -126,13 +126,23 @@ namespace polysat {
std::tuple<pdd, pdd> solver::quot_rem(pdd const& a, pdd const& b) { std::tuple<pdd, pdd> solver::quot_rem(pdd const& a, pdd const& b) {
auto& m = a.manager(); auto& m = a.manager();
unsigned sz = m.power_of_2(); unsigned sz = m.power_of_2();
pdd quot = m.mk_var(add_var(sz)); if (a.is_val() && b.is_val()) {
pdd rem = m.mk_var(add_var(sz)); // TODO: just evaluate?
add_eq(b * quot + rem - a); }
add_noovfl(b, quot); pdd q = m.mk_var(add_var(sz)); // quotient
add_clause(eq(b), ult(rem, b), false); pdd r = m.mk_var(add_var(sz)); // remainder
add_ule(quot, a); // Axioms for quotient/remainder:
return std::tuple<pdd, pdd>(quot, rem); // a = b*q + r
// multiplication does not overflow in b*q
// addition does not overflow in (b*q) + r; for now expressed as: r <= bq+r
// b ≠ 0 ==> r < b
// b = 0 ==> q = -1
add_eq(b * q + r - a);
add_noovfl(b, q);
add_ule(r, b*q+r);
add_clause(eq(b), ult(r, b), false);
add_clause(diseq(b), eq(q + 1), false);
return std::tuple<pdd, pdd>(q, r);
} }
pdd solver::lshr(pdd const& p, pdd const& q) { pdd solver::lshr(pdd const& p, pdd const& q) {