Administration#

This appendix includes administrative policies and details describing the roles and responsibilities of participants. It is meant to be a living document, more descriptive than prescriptive. It should be a basis for future decision making, using past decisions as a prior. Changes to this appendix can be made by pull request with the leadership team as reviewers.

Community standards#

Be respectful. Communicate openly. Resolve disagreements peacefully.

Resolution process#

If a disagreement about Celeritas can’t be immediately resolved, it’s OK to postpone resolution (maybe you need more data or more time to think, perhaps to decide it’s not important enough at the end of the day). In the case that a resolution is needed quickly (e.g., if it’s a blocking issue), it should be discussed among the core team until an agreement is reached. If the issue is still contentious, the leadership team should make an executive decision, giving weight to the appropriate capability area lead if possible.

Roles#

The roles of the Celeritas code base are related to the roles set out in the SciDAC project management plan. These roles should be reflected in the different teams and/or access restrictions in GitHub.

Code lead: The code lead is responsible for steering the technical implementation of Celeritas to meet the long-term project goals. One key responsibility of the code lead is to set up milestones for releases and execute the release process described below.
Maintainer: Maintainers should be familiar with most or all parts of the codebase and are responsible for merging pull requests and closing issues.
Core team member: The “core team” are those currently funded to work on Celeritas. Core team members are responsible for reviewing pull requests in accordance with the contributing guidelines. They should regularly contribute new code, perform code reviews, publish new results using Celeritas, and/or participate in Celeritas stand-up meetings and hackathons.
Core advisor: Advisors maintain close ties to Celeritas but are not consistently developing or validating it. They should be officially part of a Celeritas proposal or funded work even though they may charge only a small fraction of their time. Core advisors are encouraged to perform code reviews and attend meetings, and they are expected to have a leadership role in long-term project planning.
Contributor: Anyone can submit a pull request that conforms to the contribution guidelines! Contributors are recognized by including their handle and pull requests in release notes but do not otherwise have a formal role.

Role change process#

Adding or removing a member of the “core team” must be done by consensus of the leadership team (or if the core team member wants to remove themself). Adding maintainers can be done at the whim of the code lead. The team list on GitHub is the official record of roles.

Code review#

Reviewing incoming code maintains (and should improve) the quality of the codebase in the interests of correctness and long-term maintainability. If the code is reviewed according to the guidelines below, at least two people (the author and the reviewer) will be able to modify any given piece of code, increasing the bus factor.

Reviewing pull requests#

Each pull request must be reviewed by at least one member of the core team who is knowledgeable about the section of code being modified.

The review process must be based on constructive feedback (“here’s a suggestion to make this better” or “did you consider what would happen if X?”), not destructive feedback (“this code is ugly”). When reviewing, you should focus almost exclusively on the new changeset, as opposed to larger systemic issues, or smaller problems with nearby sections of code that you happen to notice. If you do find such issues and they can reasonably be bundled into the submitted change set, you can work with the author to incorporate the changes, create a follow-on pull request yourself, or open an issue for later.

Try to fully review the entirety of the changeset on your first review, but if major changes are needed it’s a good idea to pause, submit your comments so far, and work with the PR author to address the major issues before continuing to the next review iteration.

The correctness of the new code must be ensured by comparing against references, verifying the new code is sufficiently tested, and/or running regression problems on the incoming branch. Physics code should be compared against reference papers and other codes such as Geant4.

Ensure readability and maintainability by checking that the code and style guidelines have been followed in the new code. Balance the desire for readability with the need to avoid bikeshedding by asking yourself whether your requests are substantive enough to merit a new pull request. Perfect is the enemy of good.

Check that the title meets the requirements below, that the description is adequate, and that the appropriate labels are set.

By the time you’ve finished the code review, you should understand the code well enough to maintain it (by extension or modification) in the future.

PR titles#

The title should be an imperative statement (title-cased first word, no trailing punctuation) summarizing its effect on the user. For example:

Implement the FooBar model [enhancement, physics]

Handle errors in track initialization [enhancement, orange]

Fix sampling of low-energy Celeritons [bug, physics]

Refactor code in preparation for new tracker type [minor, orange]

Add CI support for multiple Geant4 versions [enhancement, documentation]

Avoid tags in the title.

PR description#

The description should summarize or enumerate the main changes in the pull request. Illustrative images are recommended if possible!

Label descriptions#

The labels used in Celeritas GitHub pull requests and issues have specific meanings. There should be one “change type” and one “category” selected. A few special labels (“backport”, “performance”) can also be added when appropriate.

Change type#

The change types are used to categorize changes in the release notes. If a pull request seems like it should have multiple change types, it should probably be broken up into multiple pull requests.

Bug: Report or fix an error that a user could encounter.
Documentation: Add new tests, documentation, or personal user presets without any changes in the library or applications.
Enhancement: Request or add something new to the code.
Minor: Refactor code or make small changes that should be effectively invisible to users and probably not reported.

Category#

These should be fixes, changes, or enhancements to support…

App: front end applications (celer-g4 and celer-sim).
Core: core infrastructure such as platform portability.
External: integration with external libraries such as Geant4, VecGeom, and ROOT.
Field: magnetic field propagation, linear propagation, and safety distance calculation.
ORANGE: the Celeritas geometry library for GPU tracking.
Performance: performance optimization on GPU and CPU.
Physics: particles, processes, and stepping algorithms.
User: hits and track diagnostics (i.e., extracting data from tracks running on the GPU).

Merging#

The GitHub settings for Celeritas currently require that before merging:

The branch must be up-to-date with upstream develop. This ensures that there are no failures from “implicit” conflicts (where no code actually generates a git conflict, but some new requirement or change upstream has not been implemented in the new branch). An “Update branch” button is available on the pull request page to ensure this requirement is met.
The GitHub Action CI checks must pass. There are a small matrix of core combinations that cover most potential build issues. These do not execute GPU code but they will build it and ensure that the tests pass when the Celeritas device capability is disabled.

Celeritas uses the “squash and merge” process to ensure continuity of the code history and provide easy bisecting because all commits pass all tests. Squashing eliminates the potential of broken commits and relieves developers of the burden of worrying about clean commit messages within a branch.

Since there are few enough merge requests these days, only maintainers may commit a merge. When merging, check that the commit title matches the issue title (it may be inconsistent if the branch has only a single commit), and that the “co-author” tags at the bottom of the commit message accurately reflect contributions (co-authorship may be erroneously attributed for a simple merging of the main branch into the development branch).

Releases#

Celeritas uses Semantic Versioning to enumerate releases. During its initial development phase, 0.x.0 is a major release and 0.x.z is a patch release. When Celeritas is declared stable, x.0.0 is a major release, x.y.0 is a minor release, and x.y.z is a patch release.

Major and minor releases (including 0.x.0 development releases) must have a milestone in the git issue tracker with a list of issues that can be assigned. Only major releases can remove features and change public-facing APIs. Minor releases can deprecate features. Both major and minor releases should include notable improvements to the code.

Patch releases can be created at any time but should typically include at least one critical bug fix or several substantial fixes. Patch releases should focus almost exclusively on fixes and should generally not include new features or other major code changes.

Release process#

Releases can be created from the primary “develop” branch (major, minor, patch) or a “backport” branch (minor, patch). The following process must be followed (and may need iteration to converge) for each release.

Ensure all CI jobs pass for the target branch to be released (develop or backports/vX.Y). This is automatic for releases from the develop branch, since every pull request must pass, but should be checked manually for backports.
Create a release-vX.Y.Z branch from upstream/develop.
If creating a new release from develop, tag the target branch with vX.Y.Z-rc.N where N starts with 1, and increment for every time you return to this step due to new pull requests. The tag can be pushed to your fork, or to the main repository if it should be shared with other team members.
Run performance regression tests on Perlmutter (for performance testing), Frontier (for HIP testing), and an additional machine with debug assertions enabled (e.g., Wildstyle).
[TODO: define high-level validation tests like geant-val and a test matrix correlating capability areas (code files/directories changed) to test names.] Rerun and perform a cursory check on all validation tests that might be affected by changes since the previous release. More complete validation (since a change in results might not be an error) can be done separately.
Postpone the release temporarily if major new bugs or performance regressions are detected. Create new pull requests for the serious errors using the standard contributing process, and once the fixes are merged into develop, merge develop into the release branch. Return to step 2.
If only minor updates are needed to fix the build or tests on a particular machine, include those as part of the release branch.
If this is a “major” release (see Deprecations), check for and remove code marked as DEPRECATED: to be removed in vX.Y.
Update documentation with release notes from all pull requests newly included in the release. Make sure this happens after all pull requests targeted for this milestone have been merged. Follow the format for previous releases: add a summary of highlights, and enumerate the pull requests (with PR numbers and authorship attribution) separated by features and bug requests. Use the helper notebook in the Celeritas documents repository to automate this.
Submit a pull request with the newly added documentation and any release-related tweaks, and wait until it’s reviewed and merged. The unit tests and documentation should all build and pass the CI.
If releasing a backported version branch, cherry-pick this documentation commit into the backport branch.
Use the GitHub interface to create a new release with the documentation update that was just added.

After committing the release tag:

Save the tar.gz and attach to the release, because the hash changes if the git “describe” function returns a different result for the release tag’s hash (e.g., if a collaborative branch on the main repository points to that commit).
Pull locally (make sure to use the --tags option) and build PDF user documentation for the release. Ensure breathe is activated (so the API is listed) and that the version is embedded correctly. [TODO: We should add a documentation pipeline that builds and uploads to GitHub pages.]
Update the Spack recipe for Celeritas with the new version and sha256 value (either manually or using spack checksum) and submit a pull request to the Spack project.
Mark the GitHub release milestone as completed.

The first commit that deviates from the most recent major or minor branch should be tagged (but not released!) with the next version number with a -dev suffix. For example, after releasing version 1.0.0, the next commit on the develop branch that is not intended for version 1.0.1 (i.e., the first new feature) should be tagged with v1.1.0-dev, so that git describe --tags --match 'v*' shows the new features as being part of the v1.1.0 series.

Deprecations#

Deprecating obsolete code is vital to the long-term maintainability of an open-source project. As new capabilities and better interfaces replace old ones, removing the old ones is the only way to pay off technical debt. A careful deprecation process is necessary to provide users a way to transition to the newer capabilities: there must be separate releases marking code as deprecated and removing it, and removal is only allowed in major version changes.

Deprecated public APIs (functions, classes, identifiers, …) should be marked in the code with the [[deprecated]] C++ attribute and an adjacent comment “remove in vX.0”. Here, X is the next major release after the deprecation is released [1]. For example, if a function is deprecated after version 1.2 is released but a 1.3 release is planned, the comment should specify remove in v2.0. However, if the deprecation is made after the final minor version is released (i.e., on or after the v2.0-dev tag) the deprecation should be marked for v3.0.

Private APIs (those not documented in the user API documentation, not limited to classes in the detail namespace) are not subject to the deprecation policy and can be changed at will. As the Celeritas code and its use cases mature, some functionality will become public and others will become “private.” Making a public API private should be treated as a deprecation.