warning: ignoring #pragma omp parallel

[xkszltl]

🐛 Bug

I'm seeing a lot of warning: ignoring #pragma omp parallel like this:

Maybe there should be a -fopenmp?

Environment

• PyTorch / torchvision Version (e.g., 1.0 / 0.4.0): master/master
• OS (e.g., Linux): Ubuntu 18.04
• How you installed PyTorch / torchvision (conda, pip, source): source
• Build command you used (if compiling from source): cmake+ninja+gcc-8
• Python version: 3.6
• CUDA/cuDNN version: 11.0/8

[fmassa]

Thanks for the report. We don't directly use omp parallel in nms_cpu, so this might be somewhere else.

We will have a look.

[xkszltl]

@vfdev-5 Any news so far?

[vfdev-5]

@xkszltl i'll try to take a look at this issue this week.

[klvnptr]

@vfdev-5 any update? :) I'm having the same problem

[vfdev-5]

@klvnptr Sorry, seems like I missed this issue in my task list. Let me check this on monday. Thanks.

[klvnptr]

thanks for getting back @vfdev-5
for me this solved the problem:
$ apt-get install libopenmpi-dev
$ CFLAGS="-fopenmp" python3 setup.py bdist_wheel

[xkszltl]

@vfdev-5
I don't think that's the right way.

• It should be done in CMake, not setup.py, or the issue is still there when calling cmake directly.
• When adding openmp, you should use find_package(OpenMP) and link to it.
• Blindly adding -fopenmp may cause inconsistent result with pytorch's openmp. There're many openmp implementations, not just the default one.
• This could be an issue in pytorch where it doesn't expose openmp flag in dependency properly. If so issue should be forwarded to them as well.