Minor optimization in ExpandHalfToFull - #1264
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Please share perf test results
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Rebased on #1265 and squashed. |
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Don't have any. This is just an observation not related to any particular problem I've run. |
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I don't think we should merge until we have confirmed it is beneficial
No need to hammer local counts with atomics, use local variable instead.
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Pull request overview
This PR aims to reduce atomic contention in the half-to-full neighbor list expansion path (expandHalfToFull) by using precomputed local offsets and fewer atomics during counting and rewriting.
Changes:
- Optimize
expandHalfToFull()counting by batching per-row increments and skipping empty rows. - Optimize
expandHalfToFull()rewriting by writing the “forward” neighbors without atomics and placing reverse edges from the end of each row. - Refactor/adjust neighbor list fill/copy loops in
ArborX_NeighborList.hpp(but the current HalfNeighborList fill callback no longer matches its count phase).
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/spatial/detail/ArborX_NeighborList.hpp | Adjusts how half/full neighbor list entries are filled/copied; currently introduces an inconsistency in HalfNeighborList fill vs count. |
| src/spatial/detail/ArborX_ExpandHalfToFull.hpp | Reduces atomic operations in counting and rewrite phases when expanding a half neighbor list to a full neighbor list. |
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No need to hammer local counts with atomics, use local variable instead.