Add 2 new GenFilters for use by HI photon team

[harmonicoscillator]

backport of #12510

These two gen filters for Pythia8 are meant to mimic the older ones used with Pyquen, which can be found here:
https://github.com/cms-sw/cmssw/blob/CMSSW_7_5_X/GeneratorInterface/HiGenCommon/src/EcalGenEvtSelector.cc
https://github.com/cms-sw/cmssw/blob/CMSSW_7_5_X/GeneratorInterface/HiGenCommon/src/EcalGenEvtSelectorFrag.cc

@bi-ran has done some sanity checking between the old filters and new filters which can be found here:
https://twiki.cern.ch/twiki/pub/CMS/MITHIGAnalysis2015/MCFilters.pdf

We would like to include these filters in the 75X series to be used for HI MC production.

[cmsbuild]

A new Pull Request was created by @richard-cms (R. Alex Barbieri) for CMSSW_7_5_X.

It involves the following packages:

GeneratorInterface/GenFilters

@vciulli, @covarell, @thuer, @cmsbuild, @bendavid, @davidlange6, @govoni can you please review it and eventually sign? Thanks.
@mkirsano this is something you requested to watch as well.
@slava77, @Degano, @smuzaffar you are the release manager for this.

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[harmonicoscillator]

Hello,

I realize lots of other, more important things are going on now, but is there an expected timeline that this could end up in 75X? We'd really like to make official MC in 75X with these filters.

[covarell]

Hello,

For what concerns HINEcalGenSelector I cannot see why the same cannot be obtained using two instances in series of:

https://github.com/cms-sw/cmssw/blob/CMSSW_8_0_X/GeneratorInterface/GenFilters/src/MCSingleParticleFilter.cc

for example.

About multi-mother the same could be achieved e.g. modifying

https://github.com/cms-sw/cmssw/blob/CMSSW_8_0_X/GeneratorInterface/GenFilters/src/MCMultiParticleFilter.cc

to accept a vector of mothers.

Please let me know if I misunderstood something.

[harmonicoscillator]

@covarell Thanks for the comments. I will take some time to see if I can get the same results using those two filters.

[harmonicoscillator]

@covarell What is the least-intrusive method for adding a vector of mothers to https://github.com/cms-sw/cmssw/blob/CMSSW_8_0_X/GeneratorInterface/GenFilters/src/MCMultiParticleFilter.cc ?

I could add the mother vector as an untracked parameter, but sometimes that is frowned upon.

I could add the mother vector as a tracked parameter, but then all previous configs using this filter will break.

Any advice?

[harmonicoscillator]

@covarell
After some testing we can definitely remove HINEcalGenSelector in favor of the already-existing filters, thanks very much for the tip.

For PythiaFilterMultiMother, I think we have to choose one of a few options:

1. Add a new GenFilter (PythiaFilterMultiMother)
2. Extend MCMultiParticleFilter.cc with tracked parameters, potentially breaking older gen fragments
3. Extend MCMultiParticleFilter.cc with untracked parameters, which I have a working prototype for but it's causing some crashes.

I would prefer to go with option 1, since it has minimal risk for backwards compatibility, but let me know if there is strong motivation to extend MCMultiParticleFilter and I will continue working on the prototype.

[cmsbuild]

Pull request #12512 was updated. @vciulli, @covarell, @thuer, @cmsbuild, @bendavid, @davidlange6, @govoni can you please check and sign again.

[covarell]

+1

[covarell]

I do not see yet the 8_0_X version of this PR, which is needed

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/9921/console

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs after it passes the integration tests and once validation in the development release cycle CMSSW_7_6_X is complete. This pull request requires discussion in the ORP meeting before it's merged. @slava77, @davidlange6, @Degano, @smuzaffar

[harmonicoscillator]

@covarell I see you found #12510, is that sufficient for 80X version?

[cmsbuild]

+1
Tested at: 5292924
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-12512/9921/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-12512/9921/summary.html

[slava77]

This is just a feature of this release being a production release.

[slava77]

merge

80X PR is available in #12510
this is all new code MC only