Transcript CMSSW Configuration Using python

CMSSW Configuration Using python
JTERM II Tutorial
Rick Wilkinson
Why python?
Nice, readable syntax
Easy to learn
Popular
Interfaces easily to C++
Through boost::python
Why change?
Job configurations are getting big and complex
Need to easily edit configurations, both by users and
by scripts in GRID jobs
In old system, every “replace” functionality had to
be coded by hand
Some still missing, such as random access to
vectors
We’ve already had to write two systems to convert
configurations to python and back.
Downsides?
It doesn’t yet have all the “security features” the old
system had, which prevented:
Modifying a variable more than once
Modifying uncloned modules
How are we going to change?
CMSSW_1_9_0 is a closed release
All cfi’s, cff’s, and cfg’s in CVS will be translated to
python
Then, during the 2_0_0 cycle, users can switch over
How different is the syntax?
Not very different. It’s based on the old system
process DIGI = {
hcalDigis = HcalDigiProducer {
bool doNoise = true
}
…
Import FWCore.ParameterSet.Config as cms
Process = cms.Process(“DIGI”)
Process.hcalDigis = cms.EDProducer(“HcalDigiProducer”,
doNoise = cms.bool(True)
)
Translation Tools
A tool exists that will translate your file, and
automatically translate any files you include.
Sample
The process is the basic object representing the configuration.
import FWCore.ParameterSet.Config as cms
process = cms.Process(“SIM”)
# Input source
process.source = cms.Source("PoolSource",
fileNames = cms.untracked.vstring('file:gen.root')
)
# Modules
process.load(“Configuration.StandardSequences.VtxSmearedGauss_cff”)
process.load(“SimG4Core.Application.g4SimHits_cfi”)
process.g4SimHits.UseMagneticField = False
# Output
process.load(“Configuration.EventContent.EventContent_cff”)
process.FEVT = cms.OutputModule("PoolOutputModule",
process.FEVTSIMEventContent,
fileName = cms.untracked.string('sim.root')
)
# Execution paths
process.p1 = cms.Path(process.VtxSmeared+process.g4SimHits)
Modules
 Cms.EDFilter, cms.EDProducer, cms.EDAnalyzer,
cms.ESSource, cms.Service, cms.ESProducer
Execution Paths
 Cms.Sequence, cms.Path, cms.Endpath,
cms.Schedule
Including python files
A bit awkward here. Files are included differently,
depending on whether you’re in a final
configuration file, or a file to be included by
others
In your final configuration file, the file that defines
the process, other files are included by saying:
process.load(“FWCore.MessageService.MessageLogger_cfi”)
In _cfi.py and _cff.py files, you need to say:
from FWCore.MessageService.MessageLogger_cfi import *