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check feasibility immediately after tightening a bound

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2024-11-02 14:59:55 -07:00 • committed by Lev Nachmanson
parent 58e57352c2
commit 9164672d42
1 changed files with 21 additions and 30 deletions
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51
src/math/lp/dioph_eq.cpp
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@ -447,26 +447,13 @@ namespace lp {
}
lia_move tighten_with_S() {
int change = 0;
for (unsigned j = 0; j < lra.column_count(); j++) {
if (!lra.column_has_term(j) || lra.column_is_free(j) ||
lra.column_is_fixed(j) || !lia.column_is_int(j)) continue;
if (tighten_bounds_for_term_column(j)) {
change++;
}
if (!m_infeas_explanation.empty()) {
if (tighten_bounds_for_term_column(j))
return lia_move::conflict;
}
}
TRACE("dioph_eq", tout << "change:" << change << "\n";);
if (!change)
return lia_move::undef;
auto st = lra.find_feasible_solution();
if (st != lp::lp_status::FEASIBLE && st != lp::lp_status::OPTIMAL && st != lp::lp_status::CANCELLED) {
lra.get_infeasibility_explanation(m_infeas_explanation);
return lia_move::conflict;
}
}
return lia_move::undef;
}
@ -503,7 +490,7 @@ namespace lp {
}
// j is the index of the column representing a term
// return true if a new tighter bound was set on j
// return true if a conflict was found
bool tighten_bounds_for_term_column(unsigned j) {
term_o term_to_tighten = lra.get_term(j); // copy the term aside
std::queue<unsigned> q;
@ -534,18 +521,15 @@ namespace lp {
TRACE("dioph_eq", tout << "after process_q_with_S\nt:"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
tout << "g:" << g << std::endl; /*tout << "dep:"; print_dep(tout, m_tmp_l) << std::endl;*/);
if (g.is_one()) {
TRACE("dioph_eq", tout << "g is one" << std::endl;);
return false;
} else if (g.is_zero()) {
if (g.is_one()) return false;
if (g.is_zero()) {
handle_constant_term(j);
if (!m_infeas_explanation.empty())
return true;
return false;
return !m_infeas_explanation.empty();
}
// g is not trivial, trying to tighten the bounds
// by using bitwise to explore both bounds
return tighten_bounds_for_term(g, j, true) | tighten_bounds_for_term(g, j, false);
return tighten_bounds_for_non_trivial_gcd(g, j, true)
||
tighten_bounds_for_non_trivial_gcd(g, j, false);
}
void get_expl_from_meta_term(const lar_term& t, explanation& ex) {
@ -586,7 +570,8 @@ namespace lp {
// m_indexed_work_vector contains the coefficients of the term
// m_c contains the constant term
// m_tmp_l is the linear combination of the equations that removs the substituted variablse
bool tighten_bounds_for_term(const mpq& g, unsigned j, bool is_upper) {
// returns true iff the conflict is found
bool tighten_bounds_for_non_trivial_gcd(const mpq& g, unsigned j, bool is_upper) {
mpq rs;
bool is_strict;
u_dependency *b_dep = nullptr;
@ -597,14 +582,14 @@ namespace lp {
rs = (rs - m_c) / g;
TRACE("dioph_eq", tout << "(rs - m_c) / g:" << rs << std::endl;);
if (!rs.is_int()) {
tighten_bound_for_term_for_bound_kind(g, j, rs, is_upper, b_dep);
return true;
if (tighten_bound_kind(g, j, rs, is_upper, b_dep))
return true;
}
}
return false;
}
void tighten_bound_for_term_for_bound_kind( const mpq& g, unsigned j, const mpq & ub, bool upper, u_dependency* prev_dep) {
bool tighten_bound_kind( const mpq& g, unsigned j, const mpq & ub, bool upper, u_dependency* prev_dep) {
// ub = (upper_bound(j) - m_c)/g.
// we have x[j] = t = g*t_+ m_c <= upper_bound(j), then
// t_ <= floor((upper_bound(j) - m_c)/g) = floor(ub)
@ -627,6 +612,12 @@ namespace lp {
TRACE("dioph_eq", tout << "jterm:"; print_lar_term_L(lra.get_term(j), tout) << "\ndep:"; print_dep(tout, dep) << std::endl;
);
lra.update_column_type_and_bound(j, kind, bound, dep);
auto st = lra.find_feasible_solution();
if (st != lp::lp_status::FEASIBLE && st != lp::lp_status::OPTIMAL && st != lp::lp_status::CANCELLED) {
lra.get_infeasibility_explanation(m_infeas_explanation);
return true;
}
return false;
}
u_dependency* explain_fixed_in_meta_term(const lar_term& t) {