fix sherpa interface script - adds correct openloops path to runcard if needed

[pmillet]

backport of
#8388

"
in sherpa the path to openloops does not point to the cmssw openloops version but to the directory this cmssw release was built in ( /build/jenkins/.../ )

as a workaround the ./MakeSherpaLibs script adds the correct path to the runcard if openloops is used and no other openloops path (OL_PREFIX = ..., eg for a local openloops installation) is specified

this was tested in CMSSW_7_4_0_pre8
"

[cmsbuild]

A new Pull Request was created by @pmillet for CMSSW_7_1_X.

fix sherpa interface script - adds correct openloops path to runcard if needed

It involves the following packages:

GeneratorInterface/SherpaInterface

@vciulli, @covarell, @thuer, @cmsbuild, @nclopezo, @bendavid can you please review it and eventually sign? Thanks.
@thuer this is something you requested to watch as well.
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@Degano you are the release manager for this.
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[ghost]

@pmillet I'm trying to fix this issue in the external itself, is there an easy way to reproduce the crash?

[pmillet]

@Degano
Yes you can use the following command (e.g. in CMSSW_7_4_0_pre8):

/cvmfs/cms.cern.ch/slc6_amd64_gcc491/external/sherpa/2.1.1-odfocd/bin/Sherpa -f Run.dat_Z_NLO_fixed

You can use any runcard which uses OpenLoops. I sent you an example Runcard via mail.

[ghost]

please test

[cmsbuild]

The tests are being triggered in jenkins.

[ghost]

@pmillet Fixing the external isn't as trivial as I hoped so. We should take in cmssw this fix until Sherpa fixes it upstream as they promised for the next release.

[cmsbuild]

+1
Tested at: 46538aa
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-8471/6828/summary.html

[bendavid]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_1_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @ktf, @smuzaffar

[davidlange6]

+1