Le 14 févr. 2011 à 20:50, Olaf Foellinger a écrit :

> Today I've noticed during an upgrade that macports tries to install
> atlas. That's because it's a standard dependency of py26-numpy.
> py26-numpy also adds gcc44 this way which is quite a lot for gnucash
> users. I would recommend to omit atlas from the default dependencies of
> p25-numpy. What do you think? Should I enter a ticket for this?       

Numpy, gewissermaßen :), is a computing package: scipy uses numpy. As such, it 
strives to work as fast as possible (nobody wants to wait ten hours the result 
of a matrix inversion knowing that it can be done in ten seconds when the 
algorithm is optimized). ATLAS takes hours to compile on 32-bit machines 
because it *really tries hard* to find the most efficient algorithm for each 
BLAS routine. Besides, ATLAS can use the latest GCC version, whereas the 
Accelerate framework embedded in MacOS is probably compiled with the same 
compiler as the one furnished with Xcode. It would be worth benchmarking code 
linked with an up to date ATLAS and the Apple Accelerate framework, and see 
which wins.

IMHO, the problem is not in numpy depending on Atlas, which is correct ; it is 
in other packages depending on numpy for tasks that may involve very little of 
it (e.g. using numpy as a convenient means to get array functions). Gimp relies 
ultimately on numpy for matrix convolutions in image processing, which can take 
quite a lot of time when the size of the image is large.

FWIW
Viele Grüße auch aus Paris unter Wolken,
Vincent
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