Reduce time in Phase2TrackerDigitizer

[lgray]

Add a cache in getAlgoType() to avoid repeated calls to expensive function.

Digitizer time for phase 2 tracker reduced by about 1/3rd in ttbar with PU.

[lgray]

@cmsbuild please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/15163/console

[cmsbuild]

A new Pull Request was created by @lgray (Lindsey Gray) for CMSSW_8_1_X.

It involves the following packages:

SimTracker/SiPhase2Digitizer

@cmsbuild, @civanch, @mdhildreth, @davidlange6 can you please review it and eventually sign? Thanks.
@makortel, @sdevissc, @GiacomoSguazzoni, @rovere, @VinInn, @threus, @dgulhan this is something you requested to watch as well.
@slava77, @smuzaffar you are the release manager for this.

cms-bot commands are list here #13028

[cmsbuild]

+1
Tested at: 28dae81
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-15864/15163/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-15864/15163/summary.html

[civanch]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_8_1_X IBs (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @slava77, @davidlange6, @smuzaffar

[davidlange6]

+1
thanks!