SSE: mind the gap
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SSE: mind the gap
1–10 of 35 posts
Re: SSE: mind the gap
#2It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Re: SSE: mind the gap
#3It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Would you be able to point me towards a shipping product/library that does this? It's easy to find examples of people hardcoding x64 assembly (x264, zlib, libyuv) but I haven't stumbled across anybody making good use of a high level wrapper.
Re: SSE: mind the gap
#4It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Not sure about "single code path". Differences amid SIMD flavors are significant, there are cases when translation one-to-one is either impossible or unpractical. A bright example are AVX2 instructions operating on 128-bit lanes rather whole 256-bit registers.
And wrappers exists in the C++ ecosystem, C programmers are stuck to intrinsics.
Re: SSE: mind the gap
#5It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Would you be able to point me towards a shipping product/library that does this? It's easy to find examples of people hardcoding x64 assembly (x264, zlib, libyuv) but I haven't stumbled across anybody making good use of a high level wrapper.
Re: SSE: mind the gap
#6It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Would you be able to point me towards a shipping product/library that does this? It's easy to find examples of people hardcoding x64 assembly (x264, zlib, libyuv) but I haven't stumbled across anybody making good use of a high level wrapper.
Mentioned just in the parent, here is the link : https://github.com/p12tic/libsimdpp
Reaching 2.0 very soon (in RC phase right now), with support for VS which was lacking before.
Re: SSE: mind the gap
#7It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Not sure about "single code path". Differences amid SIMD flavors are significant, there are cases when translation one-to-one is either impossible or unpractical. A bright example are AVX2 instructions operating on 128-bit lanes rather whole 256-bit registers. And wrappers exists in the C++ ecosystem, C programmers are stuck to intrinsics.
The property of AVX and AVX2 you mentioned actually helps having single code path. If the SIMD wrapper allows parameterization on vector width (most do that), you can simply increase vector width when compiling for AVX and that's it.
Re: SSE: mind the gap
#8It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Would you be able to point me towards a shipping product/library that does this? It's easy to find examples of people hardcoding x64 assembly (x264, zlib, libyuv) but I haven't stumbled across anybody making good use of a high level wrapper.
There is entire high-lever scientific computing framework built using a SIMD wrapper: https://github.com/jfalcou/nt2.
Though I must note in this case the SIMD wrapper has significant problems. Due certain design decisions the wrapper performs suboptimally on mixed float-integer code on AVX for example.
Re: SSE: mind the gap
#9It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Would you be able to point me towards a shipping product/library that does this? It's easy to find examples of people hardcoding x64 assembly (x264, zlib, libyuv) but I haven't stumbled across anybody making good use of a high level wrapper.
Although it's way more than an SSE wrapper, the Eigen library is excellent in my experience and targets multiple platforms.
Re: SSE: mind the gap
#10It's much better to use any of the numerous SIMD wrappers such as libsimdpp or Vc and get various benefits for free. It's possible to target everything from SSE and NEON to AVX512 with what is essentially a single code path.
Realistically the vast majority of C and C++ codebases today will never touch anything more than x86 and ARM, and I wouldn't be surprised if most never even get past x86, so I don't buy the portability argument. Portability between SSE and AVX is a better argument.
But in any case, if you're using SIMD in anger, chances are you have hard performance requirements that you really care about, and a one size fits all approach is going to leave valuable performance on the table. Whether you just have to target your own servers, or any x86 CPU made in the past 6 years, or that plus NEON-equipped ARMs, it will probably be worth the effort to duplicate the code paths, especially in comparison to the initial effort of figuring out how to vectorize your problem in the first place.
And while it's nowhere near "leftpad", if you really want an SIMD wrapper and know what you're doing, it should be well within your capabilities to write your own. Maybe not quite as spiffy as the one on github, but when I get anywhere close to assembly I find that I get more value out of doing everything from scratch and truly understanding what I'm dealing with, rather than leaving anything in someone else's hands.