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snap variables to bounds when maximizing terms

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2019-03-13 15:28:50 -07:00
parent 75b1e8fe27
commit f336039da3
6 changed files with 80 additions and 69 deletions
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69
src/util/lp/lar_solver.cpp
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@ -270,9 +270,9 @@ void lar_solver::propagate_bounds_for_touched_rows(bound_propagator & bp) {
}
}
lp_status lar_solver::get_status() const { return m_status;}
lp_status lar_solver::get_status() const { return m_status; }
void lar_solver::set_status(lp_status s) {m_status = s;}
void lar_solver::set_status(lp_status s) { m_status = s; }
lp_status lar_solver::find_feasible_solution() {
m_settings.st().m_make_feasible++;
@ -453,9 +453,10 @@ void lar_solver::set_costs_to_zero(const lar_term& term) {
lp_assert(costs_are_zeros_for_r_solver());
}
void lar_solver::prepare_costs_for_r_solver(const lar_term & term) {
void lar_solver::prepare_costs_for_r_solver(const lar_term & term) {
TRACE("lar_solver", print_term(term, tout << "prepare: ") << "\n";);
if (move_non_basic_columns_to_bounds())
find_feasible_solution();
auto & rslv = m_mpq_lar_core_solver.m_r_solver;
rslv.m_using_infeas_costs = false;
lp_assert(costs_are_zeros_for_r_solver());
@ -471,13 +472,71 @@ void lar_solver::prepare_costs_for_r_solver(const lar_term & term) {
}
lp_assert(rslv.reduced_costs_are_correct_tableau());
}
bool lar_solver::move_non_basic_columns_to_bounds() {
auto & lcs = m_mpq_lar_core_solver;
bool change = false;
for (unsigned j : lcs.m_r_nbasis) {
if (move_non_basic_column_to_bounds(j))
change = true;
}
if (settings().simplex_strategy() == simplex_strategy_enum::tableau_costs)
update_x_and_inf_costs_for_columns_with_changed_bounds_tableau();
return change;
}
bool lar_solver::move_non_basic_column_to_bounds(unsigned j) {
auto & lcs = m_mpq_lar_core_solver;
auto & val = lcs.m_r_x[j];
switch (lcs.m_column_types()[j]) {
case column_type::boxed:
if (val != lcs.m_r_lower_bounds()[j] && val != lcs.m_r_upper_bounds()[j]) {
if (random() % 2 == 0)
set_value_for_nbasic_column(j, lcs.m_r_lower_bounds()[j]);
else
set_value_for_nbasic_column(j, lcs.m_r_upper_bounds()[j]);
return true;
}
break;
case column_type::lower_bound:
if (val != lcs.m_r_lower_bounds()[j]) {
set_value_for_nbasic_column(j, lcs.m_r_lower_bounds()[j]);
return true;
}
break;
case column_type::upper_bound:
if (val != lcs.m_r_upper_bounds()[j]) {
set_value_for_nbasic_column(j, lcs.m_r_upper_bounds()[j]);
return true;
}
break;
default:
if (is_int(j) && !val.is_int()) {
set_value_for_nbasic_column(j, impq(floor(val)));
return true;
}
break;
}
return false;
}
void lar_solver::set_value_for_nbasic_column(unsigned j, const impq & new_val) {
lp_assert(!is_base(j));
auto & x = m_mpq_lar_core_solver.m_r_x[j];
auto delta = new_val - x;
x = new_val;
change_basic_columns_dependend_on_a_given_nb_column(j, delta);
}
bool lar_solver::maximize_term_on_corrected_r_solver(lar_term & term,
impq &term_max) {
settings().backup_costs = false;
bool ret = false;
TRACE("lar_solver", print_term(term, tout << "maximize: ") << "\n"; print_constraints(tout););
TRACE("lar_solver", print_term(term, tout << "maximize: ") << "\n"; print_constraints(tout); tout << ", strategy = " << (int)settings().simplex_strategy() << "\n";);
switch (settings().simplex_strategy()) {
case simplex_strategy_enum::tableau_rows:
prepare_costs_for_r_solver(term);
settings().simplex_strategy() = simplex_strategy_enum::tableau_costs;