Hello!
I am encountering an inconsistency with hadd when merging more than 350 files together.
I have a histogram with just one bin containing an integer number, i.e. just counting entries.
I have 367 input files containing this histogram. If I merge them together and check the number of entries in histogram in the merged *.root file and compare it with the sum of the entries in the histograms of the single files, they do not match.
We are talking about only 1 event inconsistency within O(10M) events, but still this seems strange.
If I limit the hadd to 350 files, the comparison is fine, but not for the full amount.
I extracted the event numbers out ouf my large *.root files and created a minimum working example which reproduces the problem, see attached script.
I am using root version
/cvmfs/atlas.cern.ch/repo/ATLASLocalRootBase/x86_64/root/5.34.10-x86_64-slc6-gcc4.7/bin/root
mwe.py (1.95 KB)
nentries.txt (2.15 KB)