Re: OpenBLAS and performance

[Pjotr Prins]

On Wed, Dec 20, 2017 at 02:48:42PM +0000, Dave Love wrote:
> I wrote: 
> 
> > If you do provide some sort of threaded version for Python, then as far
> > as I remember it must use pthreads, not OpenMP, though you want the
> > OpenMP version for other purposes, and I hadn't realized there wasn't
> > one currently.
> 
> I was confused.  I see the only version of the library shipped is built
> with pthreads.  I think there should be serial, pthreads, and OpenMP
> versions, as for Fedora.  It may also be useful to provide the 64-bit
> integer versions, like Fedora; that's useful for at least a flagship
> chemistry program.

I was just stating that the default openblas package does not perform
well (it is single threaded, for one). If I compile for a target it
makes a large difference. I don't know how we can make that available
to others apart from having special packages like the one I made.

Looks to me like python-numpy could benefit, but how we deploy that as
a flavour - I have no idea.

> I also remembered the problems with 0.2.20.  I'll send a patch for the
> wrong cache size used on some x86_64 when I get a chance.

It is a stable release. So far no problems on my end using the latest
git checkout of openblas.

Pj.

--