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* avoid creating rows with  all but one fixed columns

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* pb

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* once in a while flip bounds of boxed variables during move_nbasic_to_bounds

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* flip rarely

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* flip rarely

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* flip rarely

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* return an empty model when lar_solver is not ready

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* randomly change bounded base var on demand only

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

* randomly change bounded base var on demand only

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2020-09-25 17:47:29 -07:00 • committed by GitHub
parent e775964cfd
commit 25724401cf
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GPG key ID: 4AEE18F83AFDEB23
10 changed files with 72 additions and 70 deletions
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22
src/math/lp/int_branch.cpp
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@ -25,8 +25,7 @@ namespace lp {
int_branch::int_branch(int_solver& lia):lia(lia), lra(lia.lra) {}
lia_move int_branch::operator()() {
lra.move_non_basic_columns_to_bounds();
int j = find_inf_int_base_column();
int j = find_inf_int_column();
return j == -1? lia_move::sat : create_branch_on_column(j);
}
@ -51,7 +50,7 @@ lia_move int_branch::create_branch_on_column(int j) {
}
int int_branch::find_inf_int_base_column() {
int int_branch::find_inf_int_column() {
int result = -1;
mpq range;
mpq new_range;
@ -59,19 +58,16 @@ int int_branch::find_inf_int_base_column() {
unsigned n = 0;
lar_core_solver & lcs = lra.m_mpq_lar_core_solver;
unsigned prev_usage = 0; // to quiet down the compile
unsigned k = 0;
unsigned usage;
unsigned j;
unsigned j = 0;
// this loop looks for a column with the most usages, but breaks when
// a column with a small span of bounds is found
for (; k < lra.r_basis().size(); k++) {
j = lra.r_basis()[k];
for (; j < lra.column_count(); j++) {
if (!lia.column_is_int_inf(j))
continue;
usage = lra.usage_in_terms(j);
if (lia.is_boxed(j) && (range = lcs.m_r_upper_bounds()[j].x - lcs.m_r_lower_bounds()[j].x - rational(2*usage)) <= small_range_thresold) {
result = j;
k++;
result = j++;
n = 1;
break;
}
@ -83,14 +79,12 @@ int int_branch::find_inf_int_base_column() {
result = j;
}
}
SASSERT(k == lra.r_basis().size() || n == 1);
// this loop looks for boxed columns with a small span
for (; k < lra.r_basis().size(); k++) {
j = lra.r_basis()[k];
usage = lra.usage_in_terms(j);
for (; j < lra.column_count(); j++) {
if (!lia.column_is_int_inf(j) || !lia.is_boxed(j))
continue;
SASSERT(!lia.is_fixed(j));
usage = lra.usage_in_terms(j);
new_range = lcs.m_r_upper_bounds()[j].x - lcs.m_r_lower_bounds()[j].x - rational(2*usage);
if (new_range < range) {
n = 1;