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remove slack heuristic

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2025-05-12 11:48:11 -07:00
parent fe0807f21a
commit a69b0e7f24
2 changed files with 18 additions and 71 deletions
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85
src/math/lp/lar_solver.cpp
View file

@ -172,7 +172,23 @@ namespace lp {
", external = " << equal_to_j << "\n";);
}
}
void get_infeasibility_explanation_for_inf_sign(
explanation& exp,
const vector<std::pair<mpq, unsigned>>& inf_row,
int inf_sign) const {
for (auto& [coeff, j]: inf_row) {
int adj_sign = coeff.is_pos() ? inf_sign : -inf_sign;
const column& ul = m_columns[j];
u_dependency* bound_constr_i = adj_sign < 0 ? ul.upper_bound_witness() : ul.lower_bound_witness();
svector<constraint_index> deps;
m_dependencies.linearize(bound_constr_i, deps);
for (auto d : deps) {
SASSERT(m_constraints.valid_index(d));
exp.add_pair(d, coeff);
}
}
}
}; // imp
unsigned_vector& lar_solver::row_bounds_to_replay() { return m_imp->m_row_bounds_to_replay; }
@ -1467,75 +1483,10 @@ namespace lp {
// the infeasibility sign
int inf_sign;
auto inf_row = get_core_solver().get_infeasibility_info(inf_sign);
get_infeasibility_explanation_for_inf_sign(exp, inf_row, inf_sign);
m_imp->get_infeasibility_explanation_for_inf_sign(exp, inf_row, inf_sign);
SASSERT(explanation_is_correct(exp));
}
void lar_solver::get_infeasibility_explanation_for_inf_sign(
explanation& exp,
const vector<std::pair<mpq, unsigned>>& inf_row,
int inf_sign) const {
#if 0
impq slack(0);
std_vector<unsigned> indices;
for (auto& [coeff, j] : inf_row) {
int adj_sign = coeff.is_pos() ? inf_sign : -inf_sign;
slack += coeff * (adj_sign < 0 ? get_upper_bound(j) : get_lower_bound(j));
indices.push_back(indices.size());
}
#define get_sign(_x_) (_x_.is_pos() ? 1 : (_x_.is_neg() ? -1 : 0))
int sign = get_sign(slack);
for (unsigned j = indices.size(); j-- > 0; ) {
unsigned k = m_imp->m_settings.random_next(j+1);
if (k != j)
std::swap(indices[j], indices[k]);
}
#endif
for (auto& [coeff, j]: inf_row) {
// for (unsigned k : indices) {
// const auto& p = inf_row[k];
// unsigned j = p.second;
// const mpq& coeff = p.first;
int adj_sign = coeff.is_pos() ? inf_sign : -inf_sign;
bool is_upper = adj_sign < 0;
const column& ul = m_imp->m_columns[j];
u_dependency* bound_constr_i = is_upper ? ul.upper_bound_witness() : ul.lower_bound_witness();
#if 0
if(is_upper) {
if (ul.previous_upper() != UINT_MAX) {
auto const& [_is_upper, _j, _bound, _column] = m_imp->m_column_updates[ul.previous_upper()];
auto new_slack = slack + coeff * (_bound - get_upper_bound(j));
if (sign == get_sign(new_slack)) {
//verbose_stream() << "can weaken upper j" << j << " " << coeff << " " << get_upper_bound(j) << " " << _bound << "\n";
slack = new_slack;
bound_constr_i = _column.upper_bound_witness();
}
}
}
else {
if (ul.previous_lower() != UINT_MAX) {
auto const& [_is_upper, _j, _bound, _column] = m_imp->m_column_updates[ul.previous_lower()];
auto new_slack = slack + coeff * (_bound - get_lower_bound(j));
if (sign == get_sign(new_slack)) {
//verbose_stream() << "can weaken lower j" << j << " " << coeff << " " << get_lower_bound(j) << " " << _bound << "\n";
slack = new_slack;
bound_constr_i = _column.lower_bound_witness();
}
}
}
#endif
svector<constraint_index> deps;
dep_manager().linearize(bound_constr_i, deps);
for (auto d : deps) {
SASSERT(m_imp->m_constraints.valid_index(d));
exp.add_pair(d, coeff);
}
}
}
// (x, y) != (x', y') => (x + delta*y) != (x' + delta*y')
void lar_solver::get_model(std::unordered_map<lpvar, mpq>& variable_values) const {
variable_values.clear();

4
src/math/lp/lar_solver.h
View file

@ -155,10 +155,6 @@ class lar_solver : public column_namer {
bool explanation_is_correct(explanation&) const;
bool inf_explanation_is_correct() const;
mpq sum_of_right_sides_of_explanation(explanation&) const;
void get_infeasibility_explanation_for_inf_sign(
explanation& exp,
const vector<std::pair<mpq, unsigned>>& inf_row,
int inf_sign) const;
mpq get_left_side_val(const lar_base_constraint& cns, const std::unordered_map<lpvar, mpq>& var_map) const;
void fill_var_set_for_random_update(unsigned sz, lpvar const* vars, vector<unsigned>& column_list);
bool column_represents_row_in_tableau(unsigned j);