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Use std::threads instead of TBB tasks in the o2-sim hit merger #15871

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Merged
sawenzel merged 1 commit into from
Sep 30, 2026
Merged

Use std::threads instead of TBB tasks in the o2-sim hit merger #15871

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22 changes: 15 additions & 7 deletions run/O2HitMerger.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -84,8 +84,7 @@
#endif

#include <tbb/concurrent_unordered_map.h>
#include <tbb/parallel_for_each.h>
#include <tbb/task_group.h>
#include <thread>

namespace o2
{
Expand Down Expand Up @@ -767,8 +766,9 @@ bool O2HitMerger::mergeAndFlushData()
eventheader->putInfo("prims_total", prims);
};
// the kinematics and each detector go to separate files, so we merge and flush them concurrently
tbb::task_group tasks;
tasks.run([&]() {
// plain threads, since the TBB pool teardown crashed the merger
std::vector<std::thread> tasks;
tasks.emplace_back([&]() {
reorderAndMergeMCTracks(flusheventID, mOutTree, nprimaries, subevOrdered, mcheaderhook, eventheader);

if (mOutTree) {
Expand Down Expand Up @@ -796,13 +796,15 @@ bool O2HitMerger::mergeAndFlushData()
auto& det = mDetectorInstances[id];
auto hittree = det ? mDetectorToTTreeMap[id] : nullptr;
if (hittree) {
tasks.run([&, det = det.get(), hittree]() {
tasks.emplace_back([&, det = det.get(), hittree]() {
det->mergeHitEntriesAndFlush(flusheventID, *hittree, trackoffsets, nprimaries, subevOrdered);
hittree->SetEntries(hittree->GetEntries() + 1);
});
}
}
tasks.wait();
for (auto& t : tasks) {
t.join();
}

cleanEvent(flusheventID);
LOG(info) << "Merge/flush for event " << flusheventID << " took " << timer.RealTime();
Expand All @@ -815,7 +817,13 @@ bool O2HitMerger::mergeAndFlushData()
files.push_back(mDetectorOutFiles[id]);
}
}
tbb::parallel_for_each(files, [](TFile* file) { file->Write("", TObject::kOverwrite); });
std::vector<std::thread> writers;
for (auto file : files) {
writers.emplace_back([file]() { file->Write("", TObject::kOverwrite); });
}
for (auto& t : writers) {
t.join();
}
}
return true;
}
Expand Down
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