[Numpy-discussion] Windows, blas, atlas and dlls

Sergio sergio.callegari@gmail....
Wed Feb 20 03:18:24 CST 2013

Dag Sverre Seljebotn <d.s.seljebotn <at> astro.uio.no> writes:

> On 02/18/2013 05:26 PM, rif wrote:
> > I have no answer to the question, but I was curious as to why directly
> > calling the cblas would be 10x-20x slower in the first place.  That
> > seems surprising, although I'm just learning about python numerics.
> The statement was that directly (on the Cython level) calling cblas is 
> 10x-20x slower than going through the (slow) SciPy wrapper routines. 
> That makes a lot of sense if the matrices are smalle nough.
> Dag Sverre

Soory for expressing myself badly.

I need to call cblas directly from cython, because it is faster.

I use matrix multiplication in a tight loop.

Let the speed with the standard dot be 100,

Speed using the scipy.linalg.blas routines is 200

And speed calling directly atlas from cython is 2000

Which is reasonable, since this avoids any type checking.

The point is that I need to ship an extra atlas lib to do so in windows,
notwithstanding the fact that numpy/scipy incorporate atlas in the windows build.

I was wondering if there is a way to build numpy/scipy with atlas dynamically
linked into it, in order to be able to share the atlas libs between my code and

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