refactor: improve lo[it].Intersect[By] readability and performance#756
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samber merged 2 commits intosamber:masterfrom Jan 8, 2026
Merged
refactor: improve lo[it].Intersect[By] readability and performance#756samber merged 2 commits intosamber:masterfrom
samber merged 2 commits intosamber:masterfrom
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Preallocate seen map capacity. Extract first and last list handling out of the main loop. Remove redundant map traversal by combining the reset and delete passes into a single loop. Values are now initialized to false and toggled to true when found, allowing the cleanup pass to both reset (true→false) and delete in one iteration. Move len(seen) == 0 check into loop condition, allowing early exit before processing next list when intersection becomes empty (skips redundant first iteration).
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #756 +/- ##
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+ Coverage 94.04% 94.20% +0.15%
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Files 18 18
Lines 2840 2880 +40
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+ Hits 2671 2713 +42
+ Misses 152 151 -1
+ Partials 17 16 -1
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Contributor
Author
if len(lists) == 1 {
return lists[0]
}Also, it seems that this early return case is harmful.
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Owner
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Thanks @d-enk for this new contrib. Yes, your implem seems better and leverage CPU cache. Can you make the last suggested fix ? |
The special case `if len(lists) == 1 { return lists[0] }` was buggy:
- Returned the original slice instead of a new one
- Did not deduplicate elements
Removing it allows the general algorithm to handle single lists
correctly by creating a new slice with unique elements.
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Preallocate seen map capacity.
Extract first and last list handling out of the main loop.
Remove redundant map traversal by combining the reset and delete passes into a single loop. Values are now initialized to false and toggled to true when found, allowing the cleanup pass to both reset (true→false) and delete in one iteration.
Move len(seen) == 0 check into loop condition, allowing early exit before processing next list when intersection becomes empty (skips redundant first iteration).