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5818 :: Who would I implement simd to do fast md5 checksums ?

• zulu (orginal) [2020-01-16T10:27:20+01:00] view original

  Anyone has a short how to how would one go about it ?

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• Yardanico (orginal) [2020-01-16T11:34:29+01:00] view original

  Well there are https://github.com/jackmott/nim_simd and https://github.com/bsegovia/simd.nim for some SIMD wrapping

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• Stefan_Salewski (orginal) [2020-01-16T16:47:48+01:00] view original

  https://irclogs.nim-lang.org/23-12-2019.html#16:10:45

  16:10:45 FromDiscord <mratsim> the best simd wrapper is here: https://github.com/numforge/laser/blob/master/laser/simd.nim 😉

  But he asked not about a lib, but about simd code for md5.

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• treeform (orginal) [2020-01-16T18:18:25+01:00] view original

  How I would go about it:

  • Figure out which version/instruction set of SIMD you want. If you are making it for games steam survey can help: https://dl3.pushbulletusercontent.com/5DQdDCVmL67PvSH3bY4uzzWIf6ZxwLHW/image.png if you run your own server you can just see what it supports. Most people write different paths for each SIMD set they want to support.
  • Find a C example of what you want. Like this one for example for SSE: https://github.com/crossbowerbt/md5/blob/master/md5_sse.c or AVX2: https://gist.github.com/mniip/220ba4aa1907c7887a34
  • Decide if you want to wrap the C library or reimplement it in nim. Both are valid.
  • Have fun! Always Benchmark!

  Note: your compiler might already do SIMD and you might not be able to beat it by writing your own what basically is assembly. Always Benchmark!!

  Note: if you use SIMD just for that one thing they take a while to "startup" as current in the CPU has to be shifted to power a new area in the CPU. Having a couple of random SIMD instructions in your otherwise non-SIMD program might actually make it way slower. Always Benchmark!!!

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