set serial option for TH1::Fit in BeamSpotProducer

[dan131riley]

Interactions between TMinuit thread local variables and implicit multi-threading in the evaluation of the fit are suspected to be a cause of crashes in AlcaBeamMonitor, details are in #21769 (long). This PR sets the SERIAL option to the calls to TH1::Fit, which turns off the use of IMT in the fit evaluation.

[cmsbuild]

The code-checks are being triggered in jenkins.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-22227/3376

[cmsbuild]

A new Pull Request was created by @dan131riley (Dan Riley) for master.

It involves the following packages:

RecoVertex/BeamSpotProducer

@perrotta, @ghellwig, @arunhep, @cerminar, @cmsbuild, @franzoni, @slava77, @lpernie can you please review it and eventually sign? Thanks.
@ghellwig, @makortel, @felicepantaleo, @GiacomoSguazzoni, @tocheng, @VinInn, @ebrondol, @rovere, @mmusich, @dgulhan this is something you requested to watch as well.
@davidlange6, @slava77, @fabiocos you are the release manager for this.

cms-bot commands are listed here

[fabiocos]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/26083/console Started: 2018/02/15 09:12

[cmsbuild]

+1
Tested at: 78d02cd
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-22227/26083/summary.html

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-22227/26083/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 27
• DQMHistoTests: Total histograms compared: 2465360
• DQMHistoTests: Total failures: 3
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2465188
• DQMHistoTests: Total skipped: 169
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 1.1499999999 KiB( 22 files compared)
• Checked 111 log files, 9 edm output root files, 27 DQM output files

[perrotta]

Just for the record, this is what the jenkins tests report as difference in DQM in wf 136.788 (RunSinglePh2017B), sub-directory AlcaBeamMonitor:

I can't appreciate any difference in the figure, but since this is exactly the place which this PR wants to fix, this maybe can provide some kind of info

[dan131riley]

The code paths for the chi2 and likelihood evaluations are slightly different for the kSerial vs. kMultithread execution policies even single-threaded, but it's just sums and integrals, dunno to what extent there are random numbers involved. BinToBin is .996, with a fail threshold of 0.999999999999.

I'm not really sure what to make of it, but I'd like to see this go in anyway to see if it fixes the crashes.

[perrotta]

+1

• "SERIAL" option added to the calls to TH1::Fit in RecoVertex/BeamSpotProducer BSFitter and PVFitter
• No effect on reco quantities, as expected
• Let see if it fixes the crashes observed in AlcaBeamMonitor...

[fabiocos]

@lpernie @arunhep @ghellwig could you please check? This is another fix to try to solve the long standing issue with the AlcaBeamMonitor...

[lpernie]

+1

[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. @davidlange6, @slava77, @smuzaffar, @fabiocos (and backports should be raised in the release meeting by the corresponding L2)

[fabiocos]

+1