BeamSpot Fitter: added parameters to the migrad functor to supersede EDM defaults

[menasce]

Minuit changed the EDM (Estimated Distance to Minimum) default values after ROOT V5.35.
In order to reach the same convergence as with the old Minuit, we had to set the same default value: this has been accomplished using a polymorphic functor of migrad which accepts user-defined values.
This was a suggestion of Lorenzo Moneta, who helped us identify the problem of different convergence between old and new Minuit versions.

This fixed the problem: fits are now identical (within a factor of 10^-6)

[cmsbuild]

A new Pull Request was created by @menasce for CMSSW_7_5_X.

BeamSpot Fitter: added parameters to the migrad functor to supersede EDM defaults

It involves the following packages:

RecoVertex/BeamSpotProducer

@diguida, @cvuosalo, @cerminar, @cmsbuild, @slava77, @mmusich can you please review it and eventually sign? Thanks.
@makortel, @GiacomoSguazzoni, @rovere, @VinInn, @appeltel, @cerati, @dgulhan 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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[diguida]

please test

[diguida]

@menasce please open a corresponding one in 76X.

[rmanzoni]

@diguida here you are #9858

[cmsbuild]

The tests are being triggered in jenkins.

[cmsbuild]

+1
Tested at: 2c22cd5
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-9852/50/summary.html

[diguida]

+1
@slava77 thanks for confirming that the BS computation is ok.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs once checked with relvals in the development release cycle of CMSSW (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @Degano, @smuzaffar

[davidlange6]

+1