[red-knot] make large-union benchmark slow again#17418
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CodSpeed Performance ReportMerging #17418 will degrade performances by 98.64%Comparing Summary
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sharkdp
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Apr 16, 2025
dcreager
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* main: (44 commits) [`airflow`] Extend `AIR311` rules (#17422) [red-knot] simplify union size limit handling (#17429) [`airflow`] Extract `AIR311` from `AIR301` rules (`AIR301`, `AIR311`) (#17310) [red-knot] set a size limit on unions of literals (#17419) [red-knot] make large-union benchmark slow again (#17418) [red-knot] optimize building large unions of literals (#17403) [red-knot] Fix comments in type_api.md (#17425) [red-knot] Do not assume that `x != 0` if `x` inhabits `~Literal[0]` (#17370) [red-knot] make large-union benchmark more challenging (#17416) [red-knot] Acknowledge that `T & anything` is assignable to `T` (#17413) Update Rust crate clap to v4.5.36 (#17381) Raise syntax error when `\` is at end of file (#17409) [red-knot] Add regression tests for narrowing constraints cycles (#17408) [red-knot] Add some knowledge of `__all__` to `*`-import machinery (#17373) Update taiki-e/install-action digest to be7c31b (#17379) Update Rust crate mimalloc to v0.1.46 (#17382) Update PyO3/maturin-action action to v1.49.1 (#17384) Update Rust crate anyhow to v1.0.98 (#17380) dependencies: switch from `chrono` to `jiff` Update Rust crate bstr to v1.12.0 (#17385) ...
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Summary
Now that we've made the large-unions benchmark fast, let's make it slow again!
This adds a following operation (checking
len) on the large union, which is slow, even though building the large union is now fast. (This is also observed in a real-world code sample.) It's slow because for every element of the union, we fetch its__len__method and check it for compatibility withSized.We can make this fast by extending the grouped-types approach, as discussed in #17403, so that we can do this
__len__operation (which is identical for every literal string) just once for all literal strings, instead of once per literal string type in the union.Until we do that, we can make this acceptably fast again for now by setting a lowish limit on union size, which we can increase in the future when we make it fast. This is what I'll do in the next PR.
Test Plan
cargo bench --bench red_knot