Add new XMSX Hash - Githubissues

rurban / smhasher

Hash function quality and speed tests

https://rurban.github.io/smhasher/

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Add new XMSX Hash #280

Closed dlebed closed 11 months ago

dlebed commented 11 months ago

XMSX (XOR - Multiply - Shift - XOR) Hash Inspired by MUM and Murmur hashes

Design inputs:

be faster than SW CRC32 on modern 32-bit CPUs (and microcontrollers) (supporting HW 32bx32b->64b multiplication)
be as simple as possible (small code size)
try to reuse the same core round function (xor-mul-shift-xor)
provide reasonable hashing quality (pass SMHasher tests)

XMSX32 passes all SMHasher tests (2 bad seeds) XMSX64 currently fails one MomentChi2 test (might be fixed later)

rurban commented 11 months ago

It's extremely small, not particularly fast, but without the original MUM problems. The 64bit variant uses a very bad high word mixing.

dlebed commented 11 months ago

Thanks @rurban. Initially my goal was to get a small good enough hash for 32-bit platforms to use instead of byte-wise CRC32. On platforms like MCUs and other 32-bit CPUs it is quite fast, but yes, it was not designed to be vectorized or take advantage of 64-bit CPUs. Other "fast" hashes that could vectorized and runs faster on x64 or top ARM cores in reality are quite slower that this simple hash on mid- and low-end 32-bit CPUs. 64-bit version is just a free "add-on", maybe I even should remove it or improve mixing there later, we'l see.

rurban commented 11 months ago

I would just remove it, or use a better mixer for the higher word.

dlebed commented 11 months ago

Makes sense. Let me remove 64-bit version for now. If I'll have time to improve 64-bit version it anyway will be a different hash and could be added later.

Removing xmsx64 for now https://github.com/rurban/smhasher/pull/281