Performance of HistFactory::MakeModelAndMeasurementFast


We have recently ran into an issue where creating a workspace using HistFactory took a very long time. We ran VTune profiling to try to identify if there is some issue in the preprocessing we do, but it turns out that most of the time is actually spent inside MakeModelAndMeasurementFast method of HistFactory.
You can find the VTune output folder here: CERNBox

Note that it will also show some custom libraries, but from the Bottom-up summary of VTune it should be clear that the hotspots come exclusively from HistFactory, namely from THashTable, THashList and TDirectory. We were wondering if this is the expected behaviour/performance when running the code.

The code was on on lxplus using:

ROOT Version: 6.26/04
Built for linuxx8664gcc on Jun 07 2022, 16:01:16
From tags/v6-26-04@v6-26-04

Since the actual workspace comes from an ongoing analysis, we cannot share it publicly, but we might be able to share it privately with the ROOT team if it helps.

Best regards,

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I think it would be great if you share privately with us the workspace so we can investigate the slow down. @jonas has added also several improvements to teh HIstFactory and he can comment also and investigate this in detail.

Best regards,


Hi @TomasDado,

thanks a lot for reporting this! Indeed, it would be important for me to see the code and reproduce the workflow if possible.

Can you please reach out to me on mattermost about this? Would that be a good communication channel for you?


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