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linear solver

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
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Nikolaj Bjorner 2021-05-14 17:10:01 -07:00
parent 17fcf79c04
commit 683ce27c8f
8 changed files with 264 additions and 42 deletions
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27
src/math/polysat/constraint.cpp
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@ -41,6 +41,33 @@ namespace polysat {
return alloc(ule_constraint, lvl, bvar, sign, a, b, d);
}
// To do signed comparison of bitvectors, flip the msb and do unsigned comparison:
//
// x <=s y <=> x + 2^(w-1) <=u y + 2^(w-1)
//
// Example for bit width 3:
// 111 -1
// 110 -2
// 101 -3
// 100 -4
// 011 3
// 010 2
// 001 1
// 000 0
//
// Argument: flipping the msb swaps the negative and non-negative blocks
//
constraint* constraint::sle(unsigned lvl, bool_var bvar, csign_t sign, pdd const& a, pdd const& b, p_dependency_ref const& d) {
auto shift = rational::power_of_two(a.power_of_2() - 1);
return ule(lvl, bvar, sign, a + shift, b + shift, d);
}
constraint* constraint::slt(unsigned lvl, bool_var bvar, csign_t sign, pdd const& a, pdd const& b, p_dependency_ref const& d) {
auto shift = rational::power_of_two(a.power_of_2() - 1);
return ult(lvl, bvar, sign, a + shift, b + shift, d);
}
constraint* constraint::ult(unsigned lvl, bool_var bvar, csign_t sign, pdd const& a, pdd const& b, p_dependency_ref const& d) {
// a < b <=> !(b <= a)
return ule(lvl, bvar, static_cast<csign_t>(!sign), b, a, d);