[Numpy-discussion] Numpy, BLAS, and CBLAS questions

Ian Henriksen insertinterestingnamehere at gmail.com
Mon Jul 13 11:32:36 EDT 2015

On Mon, Jul 13, 2015 at 7:55 AM Nathaniel Smith <njs at pobox.com> wrote:

> On Jul 13, 2015 1:44 AM, "Eric Martin" <eric at ericmart.in> wrote:
> >
> > My procedure questions:
> > Is the installation procedure I outlined above reasonable, or does it
> contain steps that could/should be removed? Having to edit Numpy source
> seems sketchy to me. I largely came up with this procedure by looking up
> tutorials online and by trial and error. I don't want to write
> documentation that encourages people to do something in a non-optimal way,
> so if there is a better way to do this, please let me know.
> I'll leave others with more knowledge to answer your other questions, but
> if you're interested in making it easy for others to link numpy against
> these libraries, I'd suggest modifying the numpy source further, by
> submitting a patch that teaches numpy.distutils how to detect and link
> against these libraries automatically :-). There are several libraries we
> already know how to do this for that you can compare against for reference,
> and this will also help for other libraries that use blas and
> numpy.distutils, like scipy.
Supporting Eigen sounds like a great idea. BLIS would be another
one worth supporting at some point. As far as implementation goes, it may
be helpful to look at https://github.com/numpy/numpy/pull/3642 and
https://github.com/numpy/numpy/pull/4191 for the corresponding set of
changes for OpenBLAS. That could be a good starting point.
Thanks for bringing this up!
-Ian Henriksen

> > Eigen has excellent performance. On my i5-5200U (Broadwell) CPU, I
> found Eigen BLAS compiled with AVX and FMA instructions to take 3.93s to
> multiply 2 4000x4000 double matrices with a single thread, while my install
> of Numpy from ubuntu took 9s (and used 4 threads on my 2 cores). My Ubuntu
> numpy appears to built against "libblas", which I think is the reference
> implementation.
> If you're using the numpy packages distributed by Ubuntu, then it should
> be possible to switch to openblas just by apt installing openblas and then
> maybe fiddling with update-alternatives.
> -n
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