# Custom optimized hash tables with UInt64 keys, lower level than Dict for ultra speed

**URL:** <https://discourse.julialang.org/t/custom-optimized-hash-tables-with-uint64-keys-lower-level-than-dict-for-ultra-speed/113831>\
**Category:** Performance\
**Created:** [May 4, 2024, 1:19pm UTC](https://discourse.julialang.org/t/custom-optimized-hash-tables-with-uint64-keys-lower-level-than-dict-for-ultra-speed/113831 "2024-05-04T13:19:50Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [May 4, 2024, 1:54pm UTC](https://discourse.julialang.org/t/custom-optimized-hash-tables-with-uint64-keys-lower-level-than-dict-for-ultra-speed/113831/4 "2024-05-04T13:54:28Z")

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> [@0x0f0f0f](#):
>
> Since we’re already accessing the dict via an UInt64, is there really the need for hashing?

You can easily define a custom hash function that only does `xor`: [Dictionary with custom hash function - #4 by stevengj](https://discourse.julialang.org/t/dictionary-with-custom-hash-function/49168/4)

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