AVX2 popcount implementation

[Charlyo]

Right now for x86 it seems there's only serial and AVX-512 popcount hamming implementation.

Could you also implement AVX2 based one? Can be found here.

Thank you very much.

[ashvardanian]

Yes, that can be done. I am a bit overloaded the next week. Any chance you can open a PR for this?

Looking at the replies in the thread, Wojciech's variant looks great. We just need to adjust the style, remove loop unrolling, and add references to the original.

[Charlyo]

I'm not proficient at C or C++. Would rather let someone more experienced to do the job (if that's ok).

[jianshu93]

Hello Both,

I believe libpopcnt.h has all AVX implementations of popcount: https://github.com/kimwalisch/libpopcnt

There is not need to implement an additional one. However, I think include it into this library can be useful.

Jianshu

[ashvardanian]

It's a good idea to add popcount, and libpopcnt looks nice, but we only need one routine for AVX2 Harley Seal transform. Would be easier to add those few lines of C code, than to add the first dependency update all of CI. Coincidently, ClickHouse and other users have expressed interest in bit-level operations, so I'm definitely open to PRs 🤗

[ashvardanian]

🎉 This issue has been resolved in version 3.9.0 🎉

The release is available on GitHub release

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