leanprover-community / leanprover-community/mathlib4
Performance regressions using `rintro` generally and `obtain` vs `rcases/have`
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Description
In CategoryTheory.Sites.DenseSubsite #15350, we needed to put some dsimp's before obtains and break out rintros into rcases then haves to claw back some regression in performance with v4.11.0-rc1.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with CategoryTheory.Sites.DenseSubsite and issue #15350, comparing the dsimp/obtain and rintro/rcases/have forms described there. Measure the v4.11.0-rc1 behavior to isolate the regression; done means the affected pattern and a concrete performance fix or follow-up are identified.
Written by the indexing model from the issue text.
Assessment
- Domain
- performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 30/100