Hash stability guarantees #11690
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Hash stability guarantees #11690
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alice-i-cecile
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Feb 4, 2024
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NthTensor
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Feb 6, 2024
# Objective We currently over/underpromise hash stability: - `HashMap`/`HashSet` use `BuildHasherDefault<AHasher>` instead of `RandomState`. As a result, the hash is stable within the same run. - [aHash isn't stable between devices (and versions)](https://github.com/tkaitchuck/ahash?tab=readme-ov-file#goals-and-non-goals), yet it's used for `StableHashMap`/`StableHashSet` - the specialized hashmaps are stable Interestingly, `StableHashMap`/`StableHashSet` aren't used by Bevy itself (anymore). ## Solution Add/fix documentation ## Alternatives For `StableHashMap`/`StableHashSet`: - remove them - revive bevyengine#7107 --- ## Changelog - added iteration stability guarantees for different hashmaps
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Objective
We currently over/underpromise hash stability:
HashMap/HashSetuseBuildHasherDefault<AHasher>instead ofRandomState. As a result, the hash is stable within the same run.StableHashMap/StableHashSetInterestingly,
StableHashMap/StableHashSetaren't used by Bevy itself (anymore).Solution
Add/fix documentation
Alternatives
For
StableHashMap/StableHashSet:Changelog