Disable IMT for merging of NanoAOD.

[bbockelm]

As documented in CMSCOMPPR-3348, IMT triggers a crash in ROOT due to the fact that NanoAOD adds branches to the tree. This patch is a simple workaround - we disable IMT for the merge jobs (which are single core anyway) - until the ROOT issue is resolved.

I tested this by performing:

>>> import Configuration.DataProcessing.Merge
>>> p = Configuration.DataProcessing.Merge.mergeProcess(["afile.root"],mergeNANO=True)
>>> print p.dumpPython()

and hand-inspecting the resulting python.

[cmsbuild]

A new Pull Request was created by @bbockelm (Brian Bockelman) for CMSSW_10_2_X.

It involves the following packages:

Configuration/DataProcessing

@cmsbuild, @franzoni, @fabiocos, @davidlange6 can you please review it and eventually sign? Thanks.
@Martin-Grunewald 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

[arizzi]

I think you can create the same PR on the master branch from the very same branch (I assume the usual policy apply for master vs stable branches, so the master PR is needed)

[fabiocos]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/30349/console Started: 2018/09/12 10:51
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/30362/console Started: 2018/09/12 17:21
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/30368/console Started: 2018/09/12 17:50
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/30371/console Started: 2018/09/12 22:52

[fabiocos]

+operations

the DataProcessing merge test output shows modifications consistent with the proposed change

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_10_2_X IBs after it passes the integration tests and once validation in the development release cycle CMSSW_10_3_X is complete. 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

[cmsbuild]

+1
Tested at: 35f2872
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-24508/30371/summary.html

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-24508/30371/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 2 differences found in the comparisons
• DQMHistoTests: Total files compared: 31
• DQMHistoTests: Total histograms compared: 2985426
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2985234
• DQMHistoTests: Total skipped: 190
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 30 files compared)
• Checked 129 log files, 14 edm output root files, 31 DQM output files