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Mergers: Retry with gDebug if merging fails #15153

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Merged
Barthelemy merged 1 commit into from
Mar 13, 2026
+76 −39
Merged

Mergers: Retry with gDebug if merging fails #15153

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99 changes: 60 additions & 39 deletions Utilities/Mergers/src/MergerAlgorithm.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,52 @@ auto matchCollectedToPairs(const std::vector<TObject*>& targetObjects, const std
return matchedObjects;
}

// calls the default Merge methods of TObjects
Long64_t mergeDefault(TObject* const target, TObject* const other)
{
Long64_t errorCode = 0;

TObjArray otherCollection;
otherCollection.SetOwner(false);
otherCollection.Add(other);

if (target->InheritsFrom(TH1::Class())) {
// this includes TH1, TH2, TH3
auto targetTH1 = reinterpret_cast<TH1*>(target);
if (targetTH1->TestBit(TH1::kIsAverage)) {
// Merge() does not support averages, we have to use Add()
// this will break if collection.size != 1
if (auto otherTH1 = dynamic_cast<TH1*>(otherCollection.First())) {
errorCode = targetTH1->Add(otherTH1);
}
} else {
// Add() does not support histograms with labels, thus we resort to Merge() by default
errorCode = targetTH1->Merge(&otherCollection);
}
} else if (target->InheritsFrom(THnBase::Class())) {
// this includes THn and THnSparse
errorCode = reinterpret_cast<THnBase*>(target)->Merge(&otherCollection);
} else if (target->InheritsFrom(TTree::Class())) {
auto targetTree = reinterpret_cast<TTree*>(target);
auto otherTree = reinterpret_cast<TTree*>(other);
auto targetTreeSize = estimateTreeSize(targetTree);
auto otherTreeSize = estimateTreeSize(otherTree);
if (auto totalSize = targetTreeSize + otherTreeSize; totalSize > 100000000) {
LOG(warn) << "The tree '" << targetTree->GetName() << "' would be larger than 100MB (" << totalSize << "B) after merging, skipping to let the system survive";
errorCode = 0;
} else {
errorCode = targetTree->Merge(&otherCollection);
}
} else if (target->InheritsFrom(TGraph::Class())) {
errorCode = reinterpret_cast<TGraph*>(target)->Merge(&otherCollection);
} else if (target->InheritsFrom(TEfficiency::Class())) {
errorCode = reinterpret_cast<TEfficiency*>(target)->Merge(&otherCollection);
} else {
LOG(warn) << "Object '" + std::string(target->GetName()) + "' with type '" + std::string(target->ClassName()) + "' is not one of the mergeable types, skipping";
}
return errorCode;
}

void merge(TObject* const target, TObject* const other)
{
if (target == nullptr) {
Expand Down Expand Up @@ -158,48 +204,23 @@ void merge(TObject* const target, TObject* const other)
}

} else {
Long64_t errorCode = 0;
TObjArray otherCollection;
otherCollection.SetOwner(false);
otherCollection.Add(other);

if (target->InheritsFrom(TH1::Class())) {
// this includes TH1, TH2, TH3
auto targetTH1 = reinterpret_cast<TH1*>(target);
if (targetTH1->TestBit(TH1::kIsAverage)) {
// Merge() does not support averages, we have to use Add()
// this will break if collection.size != 1
if (auto otherTH1 = dynamic_cast<TH1*>(otherCollection.First())) {
errorCode = targetTH1->Add(otherTH1);
}
} else {
// Add() does not support histograms with labels, thus we resort to Merge() by default
errorCode = targetTH1->Merge(&otherCollection);
}
} else if (target->InheritsFrom(THnBase::Class())) {
// this includes THn and THnSparse
errorCode = reinterpret_cast<THnBase*>(target)->Merge(&otherCollection);
} else if (target->InheritsFrom(TTree::Class())) {
auto targetTree = reinterpret_cast<TTree*>(target);
auto otherTree = reinterpret_cast<TTree*>(other);
auto targetTreeSize = estimateTreeSize(targetTree);
auto otherTreeSize = estimateTreeSize(otherTree);
if (auto totalSize = targetTreeSize + otherTreeSize; totalSize > 100000000) {
LOG(warn) << "The tree '" << targetTree->GetName() << "' would be larger than 100MB (" << totalSize << "B) after merging, skipping to let the system survive";
errorCode = 0;
} else {
errorCode = targetTree->Merge(&otherCollection);
}
} else if (target->InheritsFrom(TGraph::Class())) {
errorCode = reinterpret_cast<TGraph*>(target)->Merge(&otherCollection);
} else if (target->InheritsFrom(TEfficiency::Class())) {
errorCode = reinterpret_cast<TEfficiency*>(target)->Merge(&otherCollection);
} else {
LOG(warn) << "Object '" + std::string(target->GetName()) + "' with type '" + std::string(target->ClassName()) + "' is not one of the mergeable types, skipping";
}
Long64_t errorCode = mergeDefault(target, other);

if (errorCode == -1) {
LOG(error) << "Failed to merge the input object '" + std::string(other->GetName()) + "' of type '" + std::string(other->ClassName()) //
+ " and the target object '" + std::string(target->GetName()) + "' of type '" + std::string(target->ClassName()) + "'";

// we retry with debug options enabled in ROOT in hopes to get some logs explaining the issue
gDebug = true;
errorCode = mergeDefault(target, other);
gDebug = false;
if (errorCode == -1) {
LOG(error) << "Merging '" + std::string(other->GetName()) + "' and '" + std::string(target->GetName()) //
+ "' failed again after a retry for debugging purposes. See ROOT warnings for details.";
} else {
LOG(warn) << "Merging '" + std::string(other->GetName()) + "' and '" + std::string(target->GetName()) //
+ "' succeeded after retrying for debugging purposes.";
}
}
}
}
Expand Down
16 changes: 16 additions & 0 deletions Utilities/Mergers/test/test_Algorithm.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,22 @@ BOOST_AUTO_TEST_CASE(MergerSingularObjects)
delete other;
delete target;
}
{
// mismatching axes - merging should fail.
// we should run again merging with gDebug enabled to see more logs from ROOT (tested only manually by visual inspection of logs)
TH1I* target = new TH1I("obj1", "obj1", bins, min, max);
target->Fill(5);
TH1I* other = new TH1I("obj2", "obj2", bins, max, max + 10);
other->Fill(2);
other->Fill(2);

BOOST_CHECK_NO_THROW(algorithm::merge(target, other));
BOOST_CHECK_EQUAL(target->GetBinContent(target->FindBin(2)), 0);
BOOST_CHECK_EQUAL(target->GetBinContent(target->FindBin(5)), 1);

delete other;
delete target;
}
{
TH2I* target = new TH2I("obj1", "obj1", bins, min, max, bins, min, max);
target->Fill(5, 5);
Expand Down
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