[Numpy-discussion] inplace dot products
David Cournapeau
david@ar.media.kyoto-u.ac...
Fri Feb 20 05:39:49 CST 2009
Olivier Grisel wrote:
> 2009/2/20 David Warde-Farley <dwf@cs.toronto.edu>:
>
>> Hi Olivier,
>>
>> There was this idea posted on the Scipy-user list a while back:
>>
>> http://projects.scipy.org/pipermail/scipy-user/2008-August/017954.html
>>
>> but it doesn't look like he got anywhere with it, or even got a
>> response.
>>
>> I just tried it and I observe the same behaviour. A quick look at the
>> SciPy sources tells me there is something fishy.
>>
>> subroutine
>> <
>> tchar=s,d,c,z>gemm(m,n,k,alpha,a,b,beta,c,trans_a,trans_b,lda,ka,ldb,kb)
>> ! c = gemm(alpha,a,b,beta=0,c=0,trans_a=0,trans_b=0,overwrite_c=0)
>> ! Calculate C <- alpha * op(A) * op(B) + beta * C
>>
>> I don't read Fortran very well, but it seems to me as though the
>> Fortran prototype doesn't match the python prototype.
>>
>> I'll poke around a little more, but in summary: there's no numpy-
>> sanctioned way to specify an output array for a dot(), AFAIK. This is
>> a bit of an annoyance, I agree, though I seem to remember Robert Kern
>> offering a fairly compelling argument why it's hard. I just don't know
>> what that argument is :)
>>
>>
>
> Alright, thanks for the reply.
>
> Is there a canonical way /sample code to gain low level access to blas / lapack
> atlas routines using ctypes from numpy / scipy code?
>
You can just use ctypes to access ATLAS, as you would do for any
library. Or do you mean something else ?
cheers,
David
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