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ahash shouldn't be the default Hasher #473

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jedisct1 opened this issue Oct 18, 2023 · 3 comments
Open

ahash shouldn't be the default Hasher #473

jedisct1 opened this issue Oct 18, 2023 · 3 comments

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@jedisct1
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See tkaitchuck/aHash#163

It's also currently completely broken on ARM: tkaitchuck/aHash#166
@Amanieu
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Amanieu commented Oct 18, 2023

Hashbrown specifically doesn't make any guarantees about hash function security. The only reason we don't use FxHash by default is because it gives poor results if the input values are all multiples of the same value (e.g. all multiples of 4).

@jestarray
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Curious, what is the best hasher if one only cares about perf?

@thomcc
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thomcc commented Oct 27, 2023 •
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It's an unanswerable question. You can make an arbitrarily fast hasher by reducing the quality of the output. For example, only hash the first 16 bytes of input strings, or even just return a constant value. Both of those are legal Hasher implementations.

@0ba100 0ba100 mentioned this issue Oct 27, 2023
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bors added a commit that referenced this issue Oct 27, 2023
@bors
Auto merge of #479 - initiativist:fix/bump-ahash, r=Amanieu
778e235 
bump ahash version 0.8.0 -> 0.8.6

ahash 0.8.0 was yanked.

should also fix the issues mentioned in [hashbrown/issues/473](#473)

I think I ran all the necessary tests so let me know if I need to do more.
@ogxd ogxd mentioned this issue Dec 6, 2023
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@jedisct1 @Amanieu @thomcc @jestarray