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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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64
src/util/lp/int_solver.cpp
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@ -263,7 +263,7 @@ lia_move int_solver::find_cube() {
if (st != lp_status::FEASIBLE && st != lp_status::OPTIMAL) {
TRACE("cube", tout << "cannot find a feasiblie solution";);
_sp.pop();
move_non_basic_columns_to_bounds();
m_lar_solver->move_non_basic_columns_to_bounds();
find_feasible_solution();
// it can happen that we found an integer solution here
return !m_lar_solver->r_basis_has_inf_int()? lia_move::sat: lia_move::undef;
@ -296,7 +296,7 @@ lia_move int_solver::gomory_cut() {
if ((m_number_of_calls) % settings().m_int_gomory_cut_period != 0)
return lia_move::undef;
if (move_non_basic_columns_to_bounds()) {
if (m_lar_solver->move_non_basic_columns_to_bounds()) {
#if Z3DEBUG
lp_status st =
#endif
@ -441,53 +441,6 @@ int int_solver::find_any_inf_int_column_basis_first() {
return find_inf_int_nbasis_column();
}
bool int_solver::move_non_basic_column_to_bounds(unsigned j) {
auto & lcs = m_lar_solver->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;
}
bool int_solver::move_non_basic_columns_to_bounds() {
auto & lcs = m_lar_solver->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)
m_lar_solver->update_x_and_inf_costs_for_columns_with_changed_bounds_tableau();
return change;
}
void int_solver::set_value_for_nbasic_column_ignore_old_values(unsigned j, const impq & new_val) {
lp_assert(!is_base(j));
@ -498,13 +451,6 @@ void int_solver::set_value_for_nbasic_column_ignore_old_values(unsigned j, const
}
void int_solver::set_value_for_nbasic_column(unsigned j, const impq & new_val) {
lp_assert(!is_base(j));
auto & x = m_lar_solver->m_mpq_lar_core_solver.m_r_x[j];
auto delta = new_val - x;
x = new_val;
m_lar_solver->change_basic_columns_dependend_on_a_given_nb_column(j, delta);
}
void int_solver::patch_nbasic_column(unsigned j, bool patch_only_int_vals) {
auto & lcs = m_lar_solver->m_mpq_lar_core_solver;
@ -537,7 +483,7 @@ void int_solver::patch_nbasic_column(unsigned j, bool patch_only_int_vals) {
if (inf_u || l <= u) {
TRACE("patch_int",
tout << "patching with l: " << l << '\n';);
set_value_for_nbasic_column(j, l);
m_lar_solver->set_value_for_nbasic_column(j, l);
}
else {
TRACE("patch_int",
@ -546,12 +492,12 @@ void int_solver::patch_nbasic_column(unsigned j, bool patch_only_int_vals) {
}
else if (!inf_u) {
u = m_is_one ? floor(u) : m * floor(u / m);
set_value_for_nbasic_column(j, u);
m_lar_solver->set_value_for_nbasic_column(j, u);
TRACE("patch_int",
tout << "patching with u: " << u << '\n';);
}
else {
set_value_for_nbasic_column(j, impq(0));
m_lar_solver->set_value_for_nbasic_column(j, impq(0));
TRACE("patch_int",
tout << "patching with 0\n";);
}