Introduction

These pages document the RooStats / RooFit - based software tools used for statistical analysis within the Higgs PAG - combine.

Combine provides a command line interface to many different statistical techniques available inside RooFit/RooStats used widely inside CMS.

The package exists in GIT under https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit

For more information about GIT and its usage in CMS, see http://cms-sw.github.io/cmssw/faq.html

The code can be checked out from GIT and compiled on top of a CMSSW release that includes a recent RooFit/RooStats

Installation instructions

Within CMSSW (recommended)

The instructions below are for installation within a CMSSW environment. For end users that don't need to commit or do any development, the following recipes should be sufficient. To choose a release version, you can find the latest releases on github under https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit/releases

Combine v9 - recommended version

The nominal installation method is inside CMSSW. The current release targets CMSSW 11_3_X series because this release has both python2 and python3 ROOT bindings, allowing a more gradual migration of user code to python3. Combine is fully python3-compatible and can work also in 12_X releases.

cmsrel CMSSW_11_3_4
cd CMSSW_11_3_4/src
cmsenv
git clone https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit.git HiggsAnalysis/CombinedLimit
cd HiggsAnalysis/CombinedLimit

Update to a recommended tag - currently the recommended tag is v9.0.0: see release notes

cd $CMSSW_BASE/src/HiggsAnalysis/CombinedLimit
git fetch origin
git checkout v9.0.0
scramv1 b clean; scramv1 b # always make a clean build

Combine v8: CMSSW_10_2_X release series

Setting up the environment (once):

export SCRAM_ARCH=slc7_amd64_gcc700
cmsrel CMSSW_10_2_13
cd CMSSW_10_2_13/src
cmsenv
git clone https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit.git HiggsAnalysis/CombinedLimit
cd HiggsAnalysis/CombinedLimit

Update to a recommended tag - currently the recommended tag is v8.2.0: see release notes

cd $CMSSW_BASE/src/HiggsAnalysis/CombinedLimit
git fetch origin
git checkout v8.2.0
scramv1 b clean; scramv1 b # always make a clean build

SLC6/CC7 release CMSSW_8_1_X

Setting up the environment (once):

# For CC7:
export SCRAM_ARCH=slc7_amd64_gcc530
# For SLC6:
export SCRAM_ARCH=slc6_amd64_gcc530

cmsrel CMSSW_8_1_0
cd CMSSW_8_1_0/src
cmsenv
git clone https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit.git HiggsAnalysis/CombinedLimit
cd HiggsAnalysis/CombinedLimit

Update to a recommended tag - currently the recommended tag for CMSSW_8_1_X is v7.0.13:

cd $CMSSW_BASE/src/HiggsAnalysis/CombinedLimit
git fetch origin
git checkout v7.0.13
scramv1 b clean; scramv1 b # always make a clean build

Standalone compilation

The standalone version can be easily compiled using cvmfs as it relies on dependencies which are already installed at /cvmfs/cms.cern.ch/. Access to /cvmfs/cms.cern.ch/ can be obtained from lxplus machines or via CernVM. See CernVM for further details on the latter. In case you do not want to use the cvmfs area, you will need to adapt the location of the dependencies listed in both the Makefile and env_standalone.sh files.

git clone https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit.git HiggsAnalysis/CombinedLimit
cd HiggsAnalysis/CombinedLimit/ 
# git checkout <some release>
. env_standalone.sh
make -j 4

You will need to source env_standalone.sh each time you want to use the package, or add it to your login.

Standalone compilation with LCG

LCG102 contains ROOT 6.26, which at the time of writing is not available in any CMSSW release. This repo can be compiled against LCG102 with:

git clone https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit.git HiggsAnalysis/CombinedLimit
cd HiggsAnalysis/CombinedLimit
source env_lcg.sh 
make LCG=1 -j 8

Standalone compilation with conda

This recipe will work both for linux and MacOS

git clone https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit.git HiggsAnalysis/CombinedLimit
cd HiggsAnalysis/CombinedLimit

conda install --name base mamba # faster conda
mamba env create -f conda_env.yml

conda activate combine
source set_conda_env_vars.sh
# Need to reactivate
conda deactivate
conda activate combine

make CONDA=1 -j 8

Using combine from then on should only require sourcing the conda environment

conda activate combine

Note: on OS X, combine can only accept workspaces, so run text2workspace.py first. This is due to some ridiculous issue with child processes and LD_LIBRARY_PATH (see note in Makefile)

What has changed between tags?

You can generate a diff of any two tags (eg for v7.0.8 and v7.0.6) by using following the url:

https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit/compare/v7.0.6...v7.0.7

Replace the tag names in the url to any tags you which to compare.

For developers

We use the Fork and Pull model for development: each user creates a copy of the repository on github, commits their requests there and then sends pull requests for the administrators to merge.

Prerequisites

1. Register on github, as needed anyway for CMSSW development: http://cms-sw.github.io/cmssw/faq.html

2. Register your SSH key on github: https://help.github.com/articles/generating-ssh-keys 1 Fork the repository to create your copy of it: https://github.com/cms-analysis/HiggsAnalysis-CombinedLimit/fork (more documentation at https://help.github.com/articles/fork-a-repo )

You will now be able to browse your fork of the repository from https://github.com/your-github-user-name/HiggsAnalysis-CombinedLimit

Combine Tool

An additional tool for submitting combine jobs to batch/crab, developed originally for HiggsToTauTau. Since the repository contains a certain amount of analysis-specific code, the following scripts can be used to clone it with a sparse checkout for just the core CombineHarvester/CombineTools subpackage, speeding up the checkout and compile times:

git clone via ssh:

bash <(curl -s https://raw.githubusercontent.com/cms-analysis/CombineHarvester/main/CombineTools/scripts/sparse-checkout-ssh.sh)

git clone via https:

bash <(curl -s https://raw.githubusercontent.com/cms-analysis/CombineHarvester/main/CombineTools/scripts/sparse-checkout-https.sh)

make sure to run scram to compile the CombineTools package.

See the CombineHarvester documentation pages for more details on using this tool and additional features available in the full package.