Optimize load_graph to avoid O(n**2) 'not ready' tracking - #20786
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Use a set instead of a list for tracking not ready SCCs, since set provides a O(1) remove operation, instead of O(n) for lists. In a large codebase, up to 37% of CPU was spent in the list.remove call when doing a small incremental run.
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
ilevkivskyi
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Feb 12, 2026
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Good catch! Some things are only visible with a lot of files.
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Use a set instead of a list for tracking not ready SCCs, since set provides a O(1) remove operation, instead of O(n) for lists. In a large codebase, up to 37% of CPU was spent in the list.remove call when doing a small incremental run.