[SciPy-user] matrix inversion time (Python vs MATLAB)

[David Cournapeau]

josef.pktd at gmail.com wrote:
> On Sat, Jan 10, 2009 at 7:57 AM, David Cournapeau
> <david at ar.media.kyoto-u.ac.jp> wrote:
>   
>> Akshay Srinivasan wrote:
>>     
>>> 2009/1/10 Sturla Molden <sturla at molden.no>:
>>>
>>>       
>>>>> On Sat, Jan 10, 2009 at 4:57 AM, Sturla Molden <sturla at molden.no> wrote:
>>>>>
>>>>> Numpy does not come with ATLAS: it uses whatever blas/lapack you have
>>>>> available. If you don't have any, numpy has an internal copy of a
>>>>> light lapack, which is not the fastest.
>>>>>
>>>>>           
>>>> Ok. If I want to use ATLAS or MKL, must NumPy or SciPy be rebuilt? Or can
>>>> I just replace the DLL?
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>> SciPy-user at scipy.org
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>>>>
>>>>
>>>>         
>>> I don't think you need to rebuild Numpy or Scipy, if the dynamic
>>> libraries behave the same way - which I'm guessing is true.
>>>
>>>       
>> You guess wrong, there are many issues :) Names is only one problem, but
>> there is also mixed ABI conventions (passing float by value or by
>> reference, for example, which fortran runtime, etc...), which means it
>> is very difficult to reliably support dynamic linking of those libraries.
>>
>> David
>> _______________________________________________
>> SciPy-user mailing list
>> SciPy-user at scipy.org
>> http://projects.scipy.org/mailman/listinfo/scipy-user
>>
>>     
>
> How do I find out whether and which ATLAS and blas and lapack my
> installed versions of numpy/scipy are using? I misplaced the
> information and cannot find it anymore.
>
>   

python -c "import numpy; print numpy.show_config()"

Same for scipy. A reliable way to know which dll are actually linked to
a python extension is depends.exe, on windows:

http://www.dependencywalker.com/

It does not always work - in particular with the whole SxS mess on XP
and Vista, it does not always know where to find dll which are there.
Guess it is one of this amazing ability of MS platform to consistently
surprise me for its lack of reliable tools for the most basic things,

fed up with wasting my time with windows-l'y,

David