LensKit Warnings

This page documents some of the warnings LensKit emits, with explanations (and sometimes solutions).

Data Deprecations

BATCHIN: Batch inference input deprecations

The BATCHIN family of warnings were added in 2025.6 to warn about deprecated input types for batch inference (lenskit.batch), which are scheduled for removal in LensKit 2026:

• Passing a mapping of user IDs to candidate sets as the user / query list.

• Passing a data frame as the user/query list.

• Passing an iterable of bare tuples (named tuples are still supported).

See Batch Queries for currently-supported query types.

PyTorch-related warnings

TCOMP: torch.compile failures

The TCOMP LensKit warning is issued when torch.compile() fails to compile one of LensKit’s PyTorch models. In this case, LensKit will use the model without Inductor compilation. The model will still work, but performance may be reduced.

There are several reasons torch.compile may fail:

• Running LensKit on Windows (the toolchain needed for working compilation on Windows is more difficult to set up, so LensKit proactively disabled compilation on Windows).

• Using PyTorch older than 2.8 (some LensKit models use features that could not be compiled in older PyTorch versions).

• Running LensKit on a version of Python that PyTorch hasn’t added compilation support for yet (as of Oct. 2025, Python 3.14 is in this category).