3 ms·

As a developer who's micro-optimized some genetic software, I can confirm that I'd considered AVX-512 but decided against it after learning that the hardware be

As a developer who's micro-optimized some genetic software, I can confirm that I'd considered AVX-512 but decided against it after learning that the hardware being purchased by the company would not have the full AVX-512 feature set desired and it was simpler/easier to just write it in AVX2. Getting the software to also work on older/cheaper hardware made the business owner happy too.

BeeOnRope 7y ago
Which ISA did it have? Even the minimal AVX-512 ISA on any mainstream CPU (SKX) is pretty much a strict superset of AVX2.
- inetknght 7y ago
  > Which ISA did it have? Business side was considering whether to buy Skylake or Broadwell.
eyegor 7y ago
If you really care about performance, you could always compile on the target machine directly via -xhost [0] or whatever the flag is on your compiler. [0] https://software.intel.com/en-us/cpp-compiler-developer-guide-and-reference-xhost-qxhost https://software.intel.com/en-us/cpp-compiler-developer-guid...
- inetknght 7y ago
  In my case, it's GCC. The option is `-march=native -mtune=native`. The trick though is _describing_ the scalar operations in the language and getting the compiler to understand how to efficiently vectorize them. I couldn't get GCC to do it at the time (GCC-5 if I recall, though we deployed with GCC-6); maybe it was just inexperience on my part. But I ended up writing the intrinsics by hand. To be quite honest it was my first dive into SIMD and I thought it was rather fun to do.
  - ncmncm 7y ago
    -march=native implies -mtune=native. You can say -march=native -mtune=sandybridge, but there would be no point. You can say -march=sandybridge -mtune=native, usefully. It might go slower on a real sandybridge than if tuned for it, but would still work, and would go as fast as the smaller instruction mix allows on your build machine.
    - inetknght 7y ago
      I know this. I don't care. I use `-march-native -mtune=native` specifically to point other developers on the team to the two relevant compiler options. And if they don't look, nothing's lost.

BeeOnRope 7y ago

Which ISA did it have? Even the minimal AVX-512 ISA on any mainstream CPU (SKX) is pretty much a strict superset of AVX2.

inetknght 7y ago
> Which ISA did it have? Business side was considering whether to buy Skylake or Broadwell.

eyegor 7y ago

If you really care about performance, you could always compile on the target machine directly via -xhost [0] or whatever the flag is on your compiler. [0] https://software.intel.com/en-us/cpp-compiler-developer-guide-and-reference-xhost-qxhost https://software.intel.com/en-us/cpp-compiler-developer-guid...

inetknght 7y ago
In my case, it's GCC. The option is `-march=native -mtune=native`. The trick though is _describing_ the scalar operations in the language and getting the compiler to understand how to efficiently vectorize them. I couldn't get GCC to do it at the time (GCC-5 if I recall, though we deployed with GCC-6); maybe it was just inexperience on my part. But I ended up writing the intrinsics by hand. To be quite honest it was my first dive into SIMD and I thought it was rather fun to do.
- ncmncm 7y ago
  -march=native implies -mtune=native. You can say -march=native -mtune=sandybridge, but there would be no point. You can say -march=sandybridge -mtune=native, usefully. It might go slower on a real sandybridge than if tuned for it, but would still work, and would go as fast as the smaller instruction mix allows on your build machine.
  - inetknght 7y ago
    I know this. I don't care. I use `-march-native -mtune=native` specifically to point other developers on the team to the two relevant compiler options. And if they don't look, nothing's lost.