making EgammaHLTPixelMatchVarProducer thread safe

[Sam-Harper]

Dear All,

Unfortunately for some reason I cant explain, I made EgammaHLTPixelMatchVarProducer a global module when creating it. And unfortunately it uses a TF1 which is not thread safe. My apologies for this and thank you @slava77 for the spot.

Here is the fix. I also compared the variable it produces as a global module and as a stream module. I ran the standard HLT setup with 4 cores on a machine with 12 cores to ensure it was actually multithreading (400% CPU usage was observed). The results are here:
https://sharper.web.cern.ch/sharper/cms/heep/2017/Jun22nd/pmS2PreAndPostFix.png
indicating the effect is thankfully very small (no difference observed in 100K Z->ee events) However it is extremely serious hence this quick simple patch while I continue to work on #19263

It would have been sooner but been swamped with p5 operations today.

[cmsbuild]

A new Pull Request was created by @Sam-Harper for master.

It involves the following packages:

RecoEgamma/EgammaHLTProducers

@Martin-Grunewald, @silviodonato, @cmsbuild, @fwyzard, @davidlange6 can you please review it and eventually sign? Thanks.
@calderona, @rafaellopesdesa, @HuguesBrun, @lgray, @battibass this is something you requested to watch as well.
@davidlange6 you are the release manager for this.

cms-bot commands are listed here

[slava77]

@cmsbuild please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/20857/console Started: 2017/06/22 22:08

[cmsbuild]

+1
Tested at: b45cb0a
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19410/20857/summary.html

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:
e0be6a0
You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19410/20857/git-log-recent-commits
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19410/20857/git-merge-result

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19410/20857/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 22
• DQMHistoTests: Total histograms compared: 1802916
• DQMHistoTests: Total failures: 44288
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 1758462
• DQMHistoTests: Total skipped: 166
• DQMHistoTests: Total Missing objects: 0
• Checked 90 log files, 14 edm output root files, 22 DQM output files

[Martin-Grunewald]

+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 requires discussion in the ORP meeting before it's merged. @davidlange6, @smuzaffar

[davidlange6]

+1