Skip to content

General CMSSW developer guide

Tutorial: proposing changes to CMSSW

Based on http://cms-sw.github.io/tutorial.html

Before you start

Please make sure you registered to GitHub and that you have provided them a ssh public key to access your private repository.

Search for available releases

Before setting up a release search for available ones:

scram list CMSSW

This should result in some output like: 

Listing installed projects available for platform >> slc7_amd64_gcc10 <<

--------------------------------------------------------------------------------
| Project Name  | Project Version          | Project Location                  |
--------------------------------------------------------------------------------

  CMSSW           CMSSW_12_0_0_pre3          
                                         --> /cvmfs/cms.cern.ch/slc7_amd64_gcc10/cms/cmssw/CMSSW_12_0_0_pre3
  CMSSW           CMSSW_12_0_0_pre4          
                                         --> /cvmfs/cms.cern.ch/slc7_amd64_gcc10/cms/cmssw/CMSSW_12_0_0_pre4
  CMSSW           CMSSW_12_0_0_pre5          
                                         --> /cvmfs/cms.cern.ch/slc7_amd64_gcc10/cms/cmssw/CMSSW_12_0_0_pre5
...
  CMSSW           CMSSW_12_3_DBG_X_2022-02-10-2300  
                                         --> /cvmfs/cms-ib.cern.ch/week1/slc7_amd64_gcc10/cms/cmssw/CMSSW_12_3_DBG_X_2022-02-10-2300
  CMSSW           CMSSW_12_3_SKYLAKEAVX512_X_2022-02-10-2300  
                                         --> /cvmfs/cms-ib.cern.ch/week1/slc7_amd64_gcc10/cms/cmssw/CMSSW_12_3_SKYLAKEAVX512_X_2022-02-10-2300
  CMSSW           CMSSW_12_3_X_2022-02-11-1100  
                                         --> /cvmfs/cms-ib.cern.ch/week1/slc7_amd64_gcc10/cms/cmssw-patch/CMSSW_12_3_X_2022-02-11-1100

Create a CMSSW area

Set up the work area just like you used to.

cmsrel CMSSW_12_3_X_2022-02-11-1100
cd CMSSW_12_3_X_2022-02-11-1100/src
cmsenv

init git area

git cms-init --upstream-only

Checkout a few packages using git cms-addpkg

Some useful packages for developing the pixel local reconstruction in CUDA:

CUDADataFormats/SiPixelCluster/
CUDADataFormats/SiPixelDigi/
RecoLocalTracker/SiPixelClusterizer/

You can add these packages with cms-addpkg:

(You need to be in the CMSSW_12_3_X_2022-02-11-1100/src repository)

git cms-addpkg CUDADataFormats/SiPixelCluster/
git cms-addpkg CUDADataFormats/SiPixelDigi/
git cms-addpkg RecoLocalTracker/SiPixelClusterizer/

See the checked out packages in .git/info/sparse-checkout

Output of cat .git/info/sparse-checkout
/.clang-format
/.clang-tidy
/.gitignore
/CUDADataFormats/SiPixelCluster/
/CUDADataFormats/SiPixelDigi/
/RecoLocalTracker/SiPixelClusterizer/

Only build the desired packages, add/remove unwanted ones:
http://cms-sw.github.io/git-cms-addpkg.html

Fetch updates from remote 

git checkout master
git fetch [official-cmssw]
git merge official-cmssw/master master

Where official-cmssw is the remote name configured for the CMSSW offline software repository.

You can list your remote repositories with (for even more verbose output, you can stack the v-s): 

git remote -v

Conflict after PR
To resolve a conflict that appeared after proposing the changes in a PR, one should prefer rebase to merge as it keeps the commit history clean.

For a rebase, do:

git checkout <development_branch_name>
git fetch
git rebase -i <CMSSW_current_release>

It might be, that the tags for branches are only considered for your default remote, eg. my-cmssw, but the current release of CMSSW is not included in that. To resolve this, you can also try specifying the remote for the official cmssw (which is not a fork):

git rebase -i <official_cmssw_name>/<CMSSW_current_release>

Build release

scram b -j

Doing a DEBUG build for GPU development:

USER_CXXFLAGS="-g -DGPU_DEBUG -DEDM_ML_DEBUG" scram b -j

If your debug build is not working, you might need to clean your development area: 

scram b clean

Before making a PR

scram b code-format # run clang-format
scram b code-checks # run clang-tidy

Build types:

  1. Stable and pre-releases

Find out what's new in a particular release: https://cmssdt.cern.ch/SDT/ReleaseNotes/index.html.

For example for

CMSSW_12_3_0_pre2 Changes since CMSSW_12_3_0_pre1:

compare to previous

36515 from @cms-tsg-storm: Revert EI removal in TSG tests hlt created: 2021-12-16 07:48:39 merged: 2021-12-16 09:48:40

36506 from @bsunanda: Run3-TB64 Make some simple changes to the classes in SimG4CMS/HcalTestBeam simulation created: 2021-12-15 15:29:55 merged: 2021-12-16 07:05:18

36505 from @kpedro88: restrict number of events for 0T PU workflows pdmv upgrade created: 2021-12-15 10:28:32 merged: 2021-12-15 14:50:12

etc.

https://cmssdt.cern.ch/SDT/ReleaseNotes/CMSSW_12/CMSSW_12_3_0_pre2.html

  1. Integration builds

Browse available integration builds, profiling and other test results: https://cmssdt.cern.ch/SDT/html/cmssdt-ib/.

Important features include the ability to filter IBs based on

  • Flavor
  • OS
  • CPU architecture
  • Compiler

img01

Look at latest commits, PRs added for a particluar build

img02