PETSc Integration Workflows

Integration branches


The master branch (soon to be renamed) contains all features and bug fixes that are believed to be stable and will be in the next release (e.g. version 3.14). Users developing software based on recently-added features in PETSc should follow master.

New feature branches should start from master.


The release branch provides bug-fix patches for the latest release. Bug fixes for the release should be started here:

$ git checkout -b yourname/fix-component-name release

As with new features, it will be tested and later merged to release and master. Bug-fix updates (e.g. 3.14.1) are tagged on release (e.g. v3.14.1).

Contributing workflows

By submitting code, the contributor gives irretrievable consent to the redistribution and/or modification of the contributed source code as described in the PETSc open source license.

Before filing a merge request

  • Read the PETSc Style and Usage Guide

  • If your contribution can be logically decomposed into 2 or more separate contributions, submit them in sequence with different branches instead of all at once.

  • Include tests which cover any changes to the source code.

  • Run the full test suite on your machine - i.e make alltests TIMEOUT=600

  • Run source checker on your machine - i.e make checkbadSource

Submit merge request

  • git push prints a URL that can be used to create a merge request. Alternatively, use GitLab’s web interface.

  • Select the correct target branch (master or release).

  • Select appropriate labels including “workflow::Pipeline-Testing”

  • If the merge request resolves an outstanding issue), you should include a closing pattern such as “Fixes #123” in the MR’s description so that issue gets closed once the MR is merged.

Merge request from a fork

  • To use the web interface option - use the fork web page, merge requests, new merge request.

  • Select the correct target repository petsc/petsc (along with the target branch)

  • Assign the MR to one of the developers.

  • Fork users lack permissions to use pipeline resources or set labels mentioned in the workflow below. Hence one of the developers would have to help with these processes. (If necessary - ping a developer in the comments section of the MR page)

Test using gitlab pipelines

  • Test pipelines can be started/controlled from the Pipelines tab on MR page. When a merge request is created a pipeline is automatically started (with a merge with destination branch) - but goes into pause state.

  • To run this pipeline un-pause this already started pipeline (or start a new one if necessary).

  • The test pipeline status is displayed near the top of the MR page (and in the pipelines tab)

More on MR pipelines

  • Do not overdo requesting testing; it is a limited resource, so if you realize a currently running test pipeline is no longer needed, cancel it.

  • When there are failures in a some jobs - and a fix is pushed for these failures, one can try re-testing only with the previously failed jobs, before running the full pipeline. To do this, start a new pipeline (if one is not already auto-started by the MR), cancel the pipeline on the pipeline page (this cancels all the jobs in the pipeline), now retry the selected jobs by using the little retry button to the right of job name. If the selected jobs are successful - one can run the full pipeline by using the retry button at the top of the page.

  • Note the retry button at the top of pipeline page does NOT use any new changes to the branch when it retries - it retries exactly the same git commit that was previously tried (and skips the already successful jobs).

  • Please report all “odd” errors in the testing that don’t seem related to your branch in issue 360.

    1. Check the current current threads to see if it is listed and add it there, with a link to your MR (e.g. !1234). Otherwise, create a new thread.

    2. Click the three dots in the top right of the thread and select “copy link”

    3. Add this link in your MR description.

Submit merge requests for suggestions on design, etc.

  • You do not need to test the code before submitting

  • Make sure to select DRAFT at the top of the MR page

  • select the additional label “workflow::Request-For-Comment”

  • There is also a button Add a task list (next to numbered list) if you edit any Markdown-supporting text area. You can use this to add task lists to a WIP MR.

Merge request review process

  • Once the MR is tested and ready for review, change the label on the MR page to “workflow::Review”

It is the submitter’s responsibility to track the progress of the MR and ensure it gets merged to master (or release). If the pipeline tests detect problems it is the submitter’s responsibility to fix the errors.

Gitlab merge requests (MRs) use “threads” to track discussions on MR. This allows Gitlab and reviewers to track what threads are not yet resolved.

  • When introducing a new topic (thread) in reviewing a MR make sure you submit with Start thread and not the Comment green button.

  • When responding to a thread make sure to use Reply box for that thread; do not introduce a new thread or a comment.

The submitter must mark threads as resolved as they fix the related issue.

If the submitter feels the MR is not getting reviewed in a timely manner they may Assign (upper right corner of the screen) to potential reviewers and request in the discussion these same people to review by @ mentioning them.

When the merge has been approved (requires codeowners, integrator approvals), all the tests work, and all the threads have been resolved the submitter must set a label to “workflow::Ready-For-Merge” (can also assign the MR to (@sbalay) if necessary)

Docs-only changes

To allow for small, quick changes to documentation, if you have made absolutely sure that your changes only affect documentation, you may create your merge request, add the “workflow::Docs-Review-Merge” label, and assign to an integrator to review and merge.

If in doubt, use the normal review process.

Remember that documentation changes should be made to the the release branch if they apply to the release version of PETSc.

GitLab instructions

We use labels to track related groups of activities. To follow labels (such as GPU or DMNetwork) go to the labels page and click “Subscribe” on the right side of the table. All merge requests and issue submissions should supply appropriate labels.

Git instructions


  • Set your name: git config --global  "Your Name"

  • Set your email: git config --global ""

  • Do not push local branches nonexistent on upstream by default: git config --global push.default simple (older versions of git require git config --global push.default tracking)

Quick summary of Git commands for PETSc developers

Starting and working on a new feature branch

  • Make sure you start from master: git checkout master

  • Create and switch to a new feature branch:

    git checkout -b <loginname>/<affected-package>-<short-description>

    For example, Barry’s new feature branch on removing CPP in snes/ will use

    git checkout -b barry/snes-removecpp. Use all lowercase and no additional underscores.

  • Write code

  • Inspect changes: git status

  • Commit code:

    • Commit all files changed: git commit -a or

    • Commit selected files: git commit file1 file2 file1 or

    • Add new files to be committed: git add file1 file2 followed by git commit. Modified files can be added to a commit in the same way.

  • Push feature branch to the remote for review: git push -u origin barry/snes-removecpp

    (or equivalently, git push --set-upstream origin barry/snes-removecpp)

Switching between and handling branches

  • Switch: git checkout <branchname>, for example git checkout barry/snes-removecpp

  • Show local and remote-tracking branches: git branch -a

  • Show available remotes: git remote -v

  • Show all branches available on remote: git ls-remote. Use git remote show origin for a complete summary.

  • Delete local branch: git branch -d <branchname> (only after merge to master is complete)

  • Delete remote branch: git push origin :<branchname> (mind the colon in front of the branch name)

  • Checkout and track a branch available on remote: git checkout -t knepley/dm-hexfem (if you inspect other feature branches, e.g. Matt’s hexfem feature branch).

    If you have multiple remotes defined, use git checkout -t <remotename>/knepley/dm-hexfem, e.g. git checkout -t origin/knepley/dm-hexfem

  • Checkout a branch from remote, but do not track upstream changes on remote: git checkout --no-track knepley/dm-hexfem

Reading commit logs

  • Show logs: git log

  • Show logs for file or folder: git log file

  • Show changes for each log: git log -p (add file or folder name if required)

  • Show diff:

    • Current working tree: git diff path/to/file

    • To other commit: git diff <SHA1> path/to/file

    • Compare version of file in two commits: git diff <SHA1> <SHA1> path/to/file

  • Show changes that are in master, but not yet in my current branch:

    • At any path: git log ..master

    • Only affecting a path: git log ..master src/dm/impls/plex/

    • Tabulated by author: git shortlog v3.3..master src/dm/impls/plex

  • Showing branches:

    • Not yet stable: git branch --all --no-merged master

    • Will be in the next release: git branch --all --merged master

    • Remove --all to the above to not include remote tracking branches (work you have not interacted with yet).

  • Find where to fix a bug:

    • Find the bad line (e.g., using a debugger)

    • Find the commit that introduced it: git blame path/to/file

    • Find the branch containing that commit: git branch --contains COMMIT (usually one topic branch)

    • Fix bug: git checkout topic-branch-name, fix bug, git commit, make Merge Request, etc.


  • Discard changes to a file which are not yet committed: git checkout path/to/file

  • Discard all changes to the current working tree: git checkout -f

  • Forward-port local commits to the updated upstream head on master: git rebase master (on feature branch)

  • Delete local branch: git branch -D <branchname>

  • Delete remote branch: git push origin :<branchname> (only after successful integration into master)


To stay oriented when working with branches, we encourage configuring git-prompt. In the following, we will include the directory, branch name, and PETSC_ARCH in our prompt, e.g.

~/Src/petsc (master=) arch-complex
$ git checkout release
 ~/Src/petsc (release<) arch-complex

The < indicates that our copy of release is behind the repository we are pulling from. To achieve this we have the following in our .profile (for bash)

source ~/bin/  (point this to the location of your
export GIT_PS1_SHOWUPSTREAM="auto"
export PS1='\w\[\e[1m\]\[\e[35m\]$(__git_ps1 " (%s)")\[\e[0m\] ${PETSC_ARCH}\n\$ '

Tab completion

To get tab-completion for git commands, first download and then source git-completion.bash.

Writing commit messages

ComponentName: one-line explanation of commit

After a blank line, write a more detailed explanation of the commit.
Many tools do not auto-wrap this part, so wrap paragraph text at a
reasonable length. Commit messages are meant for other people to read,
possibly months or years later, so describe the rationale for the change
in a manner that will make sense later.

If any interfaces have changed, the commit should fix occurrences in
PETSc itself and the message should state its impact on users.

If this affects any known issues, include "fix #ISSUENUMBER" or
"see #ISSUENUM" in the message (without quotes). GitLab will create
a link to the issue as well as a link from the issue to this commit,
notifying anyone that was watching the issue. Feel free to link to
mailing list discussions or [petsc-maint #NUMBER].

Formatted tags in commit messages:

We have defined several standard tags you should use; this makes it easy
to search for specific types of contributions. Multiple tags may be used
in the same commit message.

* If other people contributed significantly to a commit, perhaps by
reporting bugs or by writing an initial version of the patch,
acknowledge them using tags at the end of the commit message.

Reported-by: Helpful User <>
Based-on-patch-by: Original Idea <>
Thanks-to: Incremental Improver <>

* If work is done for a particular well defined funding
source or project you should label the commit with one
or more of the tags

Funded-by: My funding source
Project: My project name
\spend 1h  or 30m

Commit message template:

In order to remember tags for commit messages you can create
a file ~/git/.gitmessage containing the tags. Then on each commit
git automatically includes these in the editor. Just remember to
always delete the ones you do not use. For example I have


Searching git on commit messages:

Once you have started using tags it is possible to search the
commit history for all contributions for a single project etc.

* Get summary of all commits Funded by a particular source
  git log --all --grep='Funded-by: P-ECP’ --reverse [-stat or -shortstat]

* Get the number of insertions
 git log --all --grep='Funded-by: P-ECP' --reverse --shortstat | grep changed | cut -f5 -d" " | awk '{total += $NF} END { print total }'

* Get the number of deletions
 git log --all --grep='Funded-by: P-ECP' --reverse --shortstat | grep changed | cut -f7 -d" " | awk '{total += $NF} END { print total }'

* Get time
 git log --all --grep='Funded-by: P-ECP' | grep Time: | cut -f2 -d":" | sed s/hours//g | sed s/hour//g |awk '{total += $NF} END { print total }'

Merge commits

Do not use -m 'useless merge statement' when performing a merge. Instead, let git merge set up a commit message in your editor. It will look something like this:

Merge branch 'master' into yourname/your-feature


(perhaps without a Conflicts section if there are no conflicts). In your editor, add a short description of why you are merging. The final commit can look something like this:

Merge branch 'master' into yourname/your-feature

Obtain symbol visibility (PETSC_INTERN), SNESSetConvergenceHistory()
bug fix, and SNESConvergedDefault() interface change.


It should either be to obtain a specific feature or because some major changes affect you. When merging to an integration branch, a short summary of the purpose of the topic branch is useful.

Developing new features

Always start new features on a fresh branch (‘topic branch’) named after what you intend to develop. Always branch from master:

(master) $ git checkout -b yourname/purpose-of-branch
Switched to a new branch 'yourname/purpose-of-branch'
(yourname/purpose-of-branch) $

The naming convention for a topic branch is

<yourname>/<affected-package>-[<affected-package>-...]-<short description>

For example, Matt’s work on finite elements for hexahedra within dmplex is carried out in the topic branch knepley/dmplex-hexfem or knepley/dmplex-petscsection-hexfem. Don’t use spaces or underscores, use lowercase letters only.

Now develop your feature, committing as you go. Write good commit messages. If you are familiar with git rebase, it can be used at this time to edit your local history, making its purpose as clear as possible for the reader. When your feature is ready for review and possible integration, run

(yourname/purpose-of-branch) $ git push --set-upstream origin yourname/purpose-of-branch

You can continue to work on this branch, and use git push to make your changes visible. Only push on your branches.

If you have long-running development of a feature, you will probably fall behind the master branch. You can replay your changes on top of the latest master using

(yourname/purpose-of-branch) $ git rebase master

Checking out (tracking) a remote branch

If you wish to work on a branch that is available on the remote (shown via git remote show origin), run

git checkout <branchname>

to create a local branch that will merge from the remote branch. If your local repository is not yet aware of the new branch at the remote repository, run git fetch and then repeat the checkout.


Every branch has a purpose. Merging into branch branch-A is a declaration that the purpose of branch-A is better served by including those commits that were in branch-B. This is achieved with the command

(branch-A) $ git merge branch-B

Topic branches do not normally contain merge commits, but it is acceptable to merge from master or from other topic branches if your topic depends on a feature or bug fix introduced there. When making such a merge, use the commit message to state the reason for the merge.

For further philosophy on merges, see