cms-sw/cmssw — pull request #2581 by VinInn (2014-02-21 13:53:21+00:00)
Title: Fast match

these modification enable the possibility to study a "faster" version of the hit matcher
that preselects the hits to match based on the track parameters
The selection is controlled by a parameter of the Matcher "PreFilter"
default is false.
to set to true just
"""
--- a/RecoLocalTracker/SiStripRecHitConverter/python/SiStripRecHitMatcher_cfi.py
+++ b/RecoLocalTracker/SiStripRecHitConverter/python/SiStripRecHitMatcher_cfi.py
@@ -3,7 +3,7 @@ import FWCore.ParameterSet.Config as cms
SiStripRecHitMatcherESProducer = cms.ESProducer("SiStripRecHitMatcherESProducer",
ComponentName = cms.string('StandardMatcher'),
NSigmaInside = cms.double(3.0),
- PreFilter = cms.untracked.bool(False)
+ PreFilter = cms.untracked.bool(True)
)
"""

the speed up obtained depends on occupancy and track density in each det-unit.
At high pileup it is expected to be significant.
for a typical JetHT sample from 2012C one saves about 25% of the time in the matcher itself
corresponding to about a 6% speed up of the total CkfTrackCandidateMakerBase.

the cost is a small inefficiency caused by a loss of about 10% of the hits on the track, as it can be seen in
the standard MTV plots for TTBar
http://innocent.home.cern.ch/innocent/FastMatchMTV/

this loss in not present al all in single particle events and seems to be constant with the increase of the pileup

The use of this optimization shall be therefore reviewed in light of the final configuration for Run 2
including cluster-charge cuts and new setup for the iterative-tracking

I have of course verified that the modifications with default configuration do not produce any regression