[R-sig-Fedora] Changing the BLAS from openblas on a F32 box

[Iñaki Ucar]

On Wed, 27 May 2020 at 21:40, Gavin Simpson <ucfagls using gmail.com> wrote:
>
> Thanks Iñaki, that is exactly what i was looking for, esp the last
> option which I have now configured as an alias for easy remembering.
>
> I can answer the question re USE_LOCKING=1. I think that using both
> those options is required to get thread-safety even if openblas was
> compiled for single thread use. I don't know to what extent Simon has
> engaged with upstream on this etc.

I've seen that there is a brief note about this in the project's wiki.
I agree that a sensible default in any distro would be to build
openblas-serial with USE_LOCKING=1. But I don't understand why there
is no recommendation upstream (or I didn't find it besides the note in
the wiki) and there's no idea about the performance penalty that we
incur doing so. I brought this topic to fedora-devel.

> All I know is that using the openblas shipped with Fedora for R is
> currently a recipe for disaster for the large GAMs we're trying to
> fit. But being able to switch to atlas temporarily is a good
> alternative.

Note that switching to openblas-openmp (libopenblaso.so) should be
thread-safe and will probably get you a better performance than Atlas.
Also, Fedora packages blis (which provides
/lib64/blisblas/libblas.so.3). It seems to be thread-safe should be
more performant than Atlas too.

-- 
Iñaki Úcar