Added Benefits

• Easier to debug– Can dump configurations or add inline printouts– Can validate files by compiling

• Can use command-line arguments, environmental variables, and higher-level Python functions

• Many free tools available– See A. Hinzmann’s talk, “Visualization of the CMS

Python Configuration System”

Design

• Mimic look and feel of old configuration.

• Result is a python data structure– Not an interactive system

• Use boost::python to translate into a C++ data structure

• Translated configurations in the release– Made scripts to automatically parse, translate,

commit, and tag configuration include fragment files

New Python Config

import FWCore.ParameterSet.Config as cms

process = cms.Process(“foo”)

process.jet50Filter = cms.EDFilter(“JetFilter”, minPt = cms.double(50.))process.jet100Filter = process.jet50Filter.clone()process.jet100Filter.minPt = 100.

process.load(“Jets.Reco.JetReco_cfi”)process.jetReco.coneSize = 0.7

process.jet50to100Filter = cms.Sequence(process.jetFilter50+~process.jetFilter100)

process.jet50to100 = cms.Path(process.jetReco*process.jet50to100Filter)

Old Custom Language

process = foo {

module jet50Filter = JetFilter {

float minPt = 50.

}

module jet100Filter = jet50Filter.clone()

jet100Filter.minPt = 100.

include “Jets/Reco/data/JetReco.cfi”

replace jetReco.coneSize = 0.7

sequence jet50to100Filter = {jetFilter50&!jetFilter100}

path jet50to100 = {jetReco, jet50to100Filter}

}

Why Switch to Python?

• Previously, CMS used a custom configuration language– Parsed using flex/bison

• Users needed to be able to copy, share, and modify fragments– Users customizing their job– Production system splitting jobs, setting random

seeds, etc.

• Required a lot of effort to support these operations for all data types

CMS Job Configuration• Complex hierarchical structure

– 24 data types– 10 module types– 11 types of execution control statements & operators

• Release contains ~6000 configuration files– 4500 shared fragments– 1400 executable job configurations

• Standard full-chain simulation job defines:– 700 modules– 150 sequences of modules– over 13,000 configurable parameters