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openblas: turn off AVX512 optimizations #60092

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merged 1 commit into from Apr 27, 2019
Merged

openblas: turn off AVX512 optimizations #60092

merged 1 commit into from Apr 27, 2019

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markuskowa
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Motivation for this change

The AVX512 optimization has a bug in openblas-0.3.5 and can also lead to slower code on Xeon Silver CPUs.

Closes #59708

Needs backport to 19.03

Things done

I checked the fix by running a benchmark test on NixOS 19.03 with the modified make flags on a Xeon Silver 4114 system. The tests that previously failed (see OpenMathLib/OpenBLAS#2029) are now working. Performance is now comparable a fixed target version with DYANMIC_ARCH=0 and TARGET=HASWELL, which is expected.

  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nix-review --run "nix-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Determined the impact on package closure size (by running nix path-info -S before and after)
  • Assured whether relevant documentation is up to date
  • Fits CONTRIBUTING.md.

@markuskowa
openblas: turn off AVX512 optimizations
7035aa7 
The AVX512 optimization has a bug in openblas-0.3.5
and can also lead to slower code on Xeon Silver CPUs.

See OpenMathLib/OpenBLAS#1955
and OpenMathLib/OpenBLAS#2029
@ofborg ofborg bot requested a review from ttuegel April 23, 2019 14:45
@markuskowa
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@GrahamcOfBorg build openblasCompat
@GrahamcOfBorg build scalapack

@FRidh FRidh changed the base branch from master to staging April 27, 2019 05:07
@FRidh FRidh merged commit 6968c4f into NixOS:staging Apr 27, 2019
@markuskowa markuskowa deleted the fix-opeblas-avx branch April 27, 2019 08:38
@markuskowa
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@FRidh thanks! Can we also backport this to 19.03 staging somehow?

@FRidh
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FRidh commented Apr 27, 2019

I don't see why not. cherry-pick -x and push to staging-19.03.

@markuskowa
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Cherry picked to staging-19.03 in 28a5c36

@dtzWill dtzWill mentioned this pull request May 1, 2019
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@ttuegel ttuegel Awaiting requested review from ttuegel

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