MC-RECO: Ability to process empty timeframes (Part 2) - #15714
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August 24, 2026 11:45
This fixes a crash in the ITS, MFT, MCH and MID digit readers when the digit tree of a timeframe has no entry. - A timeframe holds no collision at all whenever the interaction rate is low enough, and the digitiser then writes a valid tree with zero entries. - The ITS/MFT reader guarded this with an assert, which is compiled out of every production build because ENABLE_CASSERT defaults to OFF, and then dereferenced branch addresses that GetEntry had not filled. - The MCH and MID readers threw on the failed TTreeReader::Next(). - All four now send empty output and end the stream. - The two asserts in the ITS/MFT connectTree become real errors for the same reason. https://its.cern.ch/jira/browse/O2-7132 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This replaces a disabled assert with a real check in 36 ROOT-tree reader specs, so that a timeframe whose tree has no entry ends the stream instead of reading past the end. - Every one of them carried the same two lines: assert(ent < mTree->GetEntries()) with the comment "this should not happen", followed by mTree->GetEntry(ent). - ENABLE_CASSERT defaults to OFF, so the assert is compiled out of every production build and the reader then publishes branch addresses that GetEntry never filled. - A timeframe holds no collision whenever the interaction rate is low enough, which is when the trees come out empty. - The readers now end the stream, which the consumers downstream already handle. - Detectors/Upgrades/ALICE3/IOTOF is left alone: it has no ControlService. https://its.cern.ch/jira/browse/O2-7132 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Allows reconstruction to handle empty-timeframes sanely instead of crashing.