Release Notes

Since 2024, LensKit uses calendar-based versioning and includes the release notes in the primary documentation. Older release notes are on GitHub.



This is the draft policy intended for the first 2024.x release of LensKit. It is subject to change until the official release of 2024.1.

Since 2024, LensKit uses “semantic calendar versioning”. That is, it uses CalVer, so version numbers are based on the year in which the software was released. We specifically use the format YYYY.MINOR.MICRO, where MINOR is bumped with each significant revision release in a given year, and MICRO is used for small bug-fix or minor enhancement releases.

We augment this to be compatible with semantic versioning: for APIs documented to be semver-stable, we batch up breaking changes to the next new-year calendar release. This means that you can use dependency constraints that assume SemVer (e.g. Python’s compatible-version constraint ~=) on LensKit versions, and they won’t automatically pull in breaking changes to stable APIs. It is rare that breaking changes are so urgent that we cannot wait until the next year to release them.

This combination does mean that we may sometimes release a minor revision with the previous year’s major version number, if there are breaking changes in progress but not yet ready for release and we need to release new features or fixes for the current major version. This will typically happen early in the year (except for important bug fixes that need to be backported to previous stable versions).

Dependency Versioning

LensKit uses SPEC0, a new standard adopted by many packages in the scientific Python ecosystem, to decide what versions of Python and core dependencies are supported. Our CI environment includes a job that runs the tests on the oldest supported dependency versions to reduce the risk that we accidentally introduce a dependency on newer code.

We anchor dependency versions based on when the first release of a year occurs (under SemCalVer). We won’t drop support for a core dependency version mid-stream unless absolutely necessary and clearly-communicated.

As of 2024, these versions are:

  • Python 3.10

  • Pandas 1.5

  • SciPy 1.9.0

We do not currently include PyTorch in our SPEC0 version commitments, but LensKit currently works with PyTorch 2.1 and newer.