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Published 20 hours ago • verified publisher icon Exawind

SIMD Issues

Open jrood-nrel opened this issue 3 years ago • 1 comments

Explicit SIMD in Nalu-Wind has historically caused problems with segfaults and complications, and continues to do so on new architectures.

At the current date I am aware of these issues involving SIMD:

  1. -mcpu=power9 -mtune=power9 is unable to be used on Summit due to NaNs in Belos. Solution is to generalize the Summit architecture to ppc64le.
  2. -DUSE_STK_SIMD_NONE is necessary for running on the CPU on Spock and Crusher.
  3. SIMD has caused numerous segfaults in unit tests on Rhodes (the CPU nightly test machine) over the years.
  4. Alignment issues regarding SIMD require special care on certain architectures.

The current approach is for our development team to continue with SIMD disabled and look towards enabling it on new platforms if possible in the future.

jrood-nrel avatar Mar 10 '22 17:03 jrood-nrel

Trying to close some long standing issues. Looking back on this and I think we should only enable SIMD for intel compilers. I think that is really the main place it is tested/used at SNL. @tasmith4 @alanw0 do you agree?

psakievich avatar Nov 08 '22 13:11 psakievich