Switch off NNPACK on osx?

[h-vetinari]

I'm getting a test failure in conda-forge/torchvision-feedstock#28 for osx that:

[W NNPACK.cpp:79] Could not initialize NNPACK! Reason: Unsupported hardware.

Upstream sets USE_NNPACK=OFF for the osx jenkins build, but seems to have it enabled by default in CMakeLists.txt

[hmaarrfk]

is that a warning or a failure?

[hmaarrfk]

Could you make the PR for this? providing the same links you just did in the appropriate build file for reference

[isuruf]

pytorch's own conda builds don't turn off NNPACK.

[h-vetinari]

Then how to avoid the hard fail of a torchvision test? Something in the CF builds is not working with nnpack+osx...

[isuruf]

That's a question for upstream devs.

[h-vetinari]

Do we know if the error Could not initialize NNPACK! Reason: Unsupported hardware. also happens with pytorch osx packages? If not, then it would seem to be an issue with the CF builds to me...

[hmaarrfk]

i do not know.

i don't have access to a Mac laptop.

[h-vetinari]

I looked at the upstream recipes, and - as Isuru said - USE_NNPACK is set on OSX, but I don't see immediately where/how it's being pulled in (there's a recipe for an old version of nnpack that does seem used anymore).

However, the bigger issue is that nnpack on OSX requires AVX2, which I don't think we should impose (and which the azure osx CI agents don't support), at least not until the archspec stuff is ready.

[isuruf]

However, the bigger issue is that nnpack on OSX requires AVX2, which I don't think we should impose

Isn't this a runtime requirement? NNPACK is built, but is not used if the cpu doesn't support it, right?

[h-vetinari]

Well, that might be the intention, but it ends up being called even if the arch doesn't support it, which is why that torchvision test failed

[isuruf]

Seems to me like that's just a warning and the test should ignore it.

[isuruf]

The way they check if nnpack is available is by trying to initialize it https://github.com/pytorch/pytorch/blob/a9b0a921d592b328e7e80a436ef065dadda5f01b/aten/src/ATen/native/NNPACK.cpp#L115-L117 which gives a warning.