[Numpy-discussion] Scipy dot

Gael Varoquaux gael.varoquaux at normalesup.org
Fri Nov 9 11:25:50 EST 2012

On Fri, Nov 09, 2012 at 03:12:42PM +0000, Nathaniel Smith wrote:
> But what if someone compiles numpy against an optimized blas (mkl,
> say) and then compiles SciPy against the reference blas? What do you
> do then!? ;-)

This could happen. But the converse happens very often. What happens is
that users (eg on shared computing resource) ask for a scientific python
environment. The administrator than installs the package starting from
the most basic one, to the most advanced one, thus starting with numpy
that can very well build without any external blas. When he gets to scipy
he hits the problem that the build system does not detect properly the
blas, and he solves that problem.

Also, it used to be that on the major linux distributions, numpy would not
be build with an optimize lapack because numpy was in the 'base' set of
packages, but not lapack. On the contrary, scipy being in the 'contrib'
set, it could depend on lapack. I just checked, and this has been fixed
in the major distributions (Fedora, Debian, Ubuntu).

Now we can discuss with such problems should not happen, and put the
blame on the users/administrators, the fact is that they happen often. I
keep seeing environments in which np.linalg is unreasonnably slow.


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