Hadd of root files gets "Killed"

ROOT
1

Dear Experts,

I’m running into troubles when trying to use hadd to merge some root files I have.
After hanging for a while, I get the following error:

Killed

and an empty output file.
I have 520 root files with a total size of 11GB.
They live in the following directory on EOS at CERN:

/eos/lhcb/wg/FlavourTagging/tuples/development/data/B2OC/OfflineSelected/Bu2D0Pi/2015_Reco15aStrip24_Down_BHADRONCOMPLETEEVENT/

I tried to use the “-n 50” option to open small chunks of 50 files, but this didn’t fix the issue.
Am I going in the right direction? Or should I try something different?

Thanks,
Vincenzo

UPDATE: the merging worked if I use the “extreme” option -n 1 (i.e, only one file opened each time). I guess that there should be some optimal point (5, 10 files or similar).

2

Most likely with too many files open at once, the memory use of hadd is too large for your system.

Cheers,
Philippe.

3

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