Enable general gamma process for Geant4

[civanch]

PR description:

General gamma process is a new method for gamma transport available with Geant4 10.7. For Run-3 CMS this bring ~1% CPU advantage with statistically same results. For Phase-2 the speed-up should be more.

PR validation:

private

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-34564/24101

• This PR adds an extra 16KB to repository

[cmsbuild]

A new Pull Request was created by @civanch (Vladimir Ivantchenko) for master.

It involves the following packages:

• SimG4Core/Application (simulation)

@cmsbuild, @civanch, @mdhildreth can you please review it and eventually sign? Thanks.
@makortel, @cvuosalo, @rovere, @bsunanda, @fabiocos, @slomeo this is something you requested to watch as well.
@silviodonato, @dpiparo, @qliphy, @perrotta you are the release manager for this.

cms-bot commands are listed here

[civanch]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7d5caa/17021/summary.html
COMMIT: 8dd313d
CMSSW: CMSSW_12_0_X_2021-07-20-1100/slc7_amd64_gcc900
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/34564/17021/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• ROOTFileChecks: Some differences in event products or their sizes found
• Reco comparison results: 54858 differences found in the comparisons
• DQMHistoTests: Total files compared: 39
• DQMHistoTests: Total histograms compared: 2996268
• DQMHistoTests: Total failures: 294749
• DQMHistoTests: Total nulls: 202
• DQMHistoTests: Total successes: 2701295
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 4.91 KiB( 38 files compared)
• DQMHistoSizes: changed ( 10224.0 ): 0.915 KiB SiStrip/MechanicalView
• DQMHistoSizes: changed ( 250202.181 ): 0.352 KiB SiStrip/MechanicalView
• DQMHistoSizes: changed ( 25202.0 ): -0.352 KiB SiStrip/MechanicalView
• DQMHistoSizes: changed ( 7.3 ): 3.995 KiB SiStrip/MechanicalView
• Checked 165 log files, 37 edm output root files, 39 DQM output files
• TriggerResults: found differences in 14 / 38 workflows

[civanch]

+1

General gamma process uses different number of calls to the random number generator, so no regression is expected.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @silviodonato, @dpiparo, @qliphy, @perrotta (and backports should be raised in the release meeting by the corresponding L2)

[qliphy]

For the record: There is an on-going check on size change from this PR in cms-sw/cms-bot#1595

[civanch]

@qliphy , @slava77, on SIM step there should be some increase of memory due to extra data tables built at initialisation. From the report I do not understand is this value is significant or not, also do not understand if there is any effect of RECO. At least, at my tests, which are not very accurate I do not see a significant overhead.

[qliphy]

+1