Skip to content

Fix #3594 #3596

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
galabovaa merged 1 commit into from
Nov 9, 2026
Merged

Fix #3594 #3596

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
34 changes: 23 additions & 11 deletions highs/presolve/HPresolveVarBndAggregation.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,10 @@ void HPresolve::aggregateVarBounds() {
if (lb > -kHighsInf && ub < kHighsInf)
range = static_cast<double>(static_cast<HighsCDouble>(ub) - lb);

// number of VLBs (VUBs) whose origin row could be rewritten
HighsInt numVlbOrigins = 0;
HighsInt numVubOrigins = 0;

// collect VLBs: y >= coef * x + constant
// standardized form: y >= a * x + lb, where a > 0
if (lb > -kHighsInf) {
Expand All @@ -205,6 +209,7 @@ void HPresolve::aggregateVarBounds() {
colImpliedBounds{v, HighsImplications::VarBound{
static_cast<double>(newCoef),
lb, v.origin}});
if (v.origin >= 0) numVlbOrigins++;
});
}
// collect VUBs: y <= coef * x + constant
Expand All @@ -228,20 +233,27 @@ void HPresolve::aggregateVarBounds() {
colImpliedBounds{v, HighsImplications::VarBound{
static_cast<double>(newCoef),
ub, v.origin}});
if (v.origin >= 0) numVubOrigins++;
});
}

// set up cliques
vlbs.for_each([&](HighsInt binaryCol, colImpliedBounds& bounds) {
HighsInt val = bounds.originalBound.coef > 0 ? 1 : 0;
vlbsClique.emplace_back(binaryCol, val);
});
vubs.for_each([&](HighsInt binaryCol, colImpliedBounds& bounds) {
HighsInt val = bounds.originalBound.coef < 0 ? 1 : 0;
vubsClique.emplace_back(binaryCol, val);
});

// clique cover
// only bounds with an origin row can be merged, so there is nothing to do
// if no VLB and no VUB has one
if (numVlbOrigins == 0 && numVubOrigins == 0) continue;

// set up cliques for the sides with an origin row
if (numVlbOrigins > 0)
vlbs.for_each([&](HighsInt binaryCol, colImpliedBounds& bounds) {
HighsInt val = bounds.originalBound.coef > 0 ? 1 : 0;
vlbsClique.emplace_back(binaryCol, val);
});
if (numVubOrigins > 0)
vubs.for_each([&](HighsInt binaryCol, colImpliedBounds& bounds) {
HighsInt val = bounds.originalBound.coef < 0 ? 1 : 0;
vubsClique.emplace_back(binaryCol, val);
});

// clique cover (clears the covers, which stay empty without cliques)
cliquetable.cliqueCover(vlbsClique, vlbsCover);
cliquetable.cliqueCover(vubsClique, vubsCover);

Expand Down
Loading