RFC: #pragma omp simd (don't merge)

[rfschtkt]

If OpenMP 4.0 is available, use it for vectorisation.

Now how should I test this, I wonder...

[zdenop]

Just remark: Visual studio 2015 support only OpenMP 2.0 standard. For VS 2017 there is not even documentation page for it :-(
Community request for new standard was declined.

[amitdo]

For VS 2017 there is not even documentation page for it :-(

https://www.google.com/search?q=openmp+microsoft+docs
https://docs.microsoft.com/en-us/search/index?search=openmp&scope=C%2B%2B

[zdenop]

@amitdo: thanks. I misunderstand link - I was expecting that there would be option to select version 2017 in combo "Other version". I tried to search on docs.microsoft.com but nothing usefull found there.

Anyway result is still the same:

Visual C++ supports the OpenMP 2.0 standard.

[amitdo]

@zdenop

Visual C++ supports the OpenMP 2.0 standard.

From #954:

amitdo commented on Jun 6, 2017

Just a note: #pragma omp simd is not supported with MSVC.

rfschtkt commented on Jun 6, 2017

@amitdo I don't think that the laggard should set the pace, considering how relatively easy the pragma is to use.

:-)

[amitdo]

https://devblogs.microsoft.com/cppblog/msvc-backend-updates-in-visual-studio-2019-preview-2/

[zdenop]

@stweil : what about this? Even we do not suggest to use openmp, I think this could be merged for future development/test. Recent version of our most common compilers support it:

• From GCC 4.9.1, OpenMP 4.0 is fully supported
• OpenMP 4.5 has been available since Clang 3.9
• VS 2019 should support #pragma omp simd

[zdenop]

Closing this PR because function WeightMatrix::DotProduct was removed and WeightMatrix::MatrixDotVector rewritten.