[SciPy-User] [cython-users] scipy cblas return value

[Radim Řehůřek]

It's actually more serious than I though. This "double instead of float" 
apparently fails on some systems while manifesting itself as a weird slow 
down: https://groups.google.com/d/msg/gensim/6B99kdtHOZo/FSss6GgzE5IJ

We've confirmed with the person who reported it that the problem is only in 
sdot. Changing the sdot return value to `float` fixes it.

SciPy version doesn't seem to affect this (tried both 0.12 and 0.13b on the 
failing machine).

CC to Scipy people: the code is using a protected pointer from 
scipy.linalg.blas.cblas, like so: https://gist.github.com/anonymous/6659007 

Why is the required return value sometimes float and sometimes double? Is 
there a better/safer way to achieve calling numpy/scipy BLAS from cython?

Cheers,
Radim


On Tuesday, September 24, 2013 6:58:20 AM UTC+2, Robert Bradshaw wrote:
>
> _cpointer seems to be woefully undocumented, but it looks like it is a 
> C function actually returning a double not a float. 
>
> On Sun, Sep 22, 2013 at 4:54 AM, Radim Řehůřek <m... at radimrehurek.com<javascript:>> 
> wrote: 
> > Hello all, 
> > 
> > I'm trying to call sdot from scipy.linalg.blas.cblas from Cython, but it 
> > only works if I declare the return type as double (not float): 
> > 
> > https://gist.github.com/anonymous/6659007 
> > 
> > I don't know if this is a Cython issue or a SciPy issue or a BLAS 
> (vecLib) 
> > issue or a chair-keyboard issue. Could someone more knowledgeable 
> elucidate 
> > please? 
> > 
> > Cheers, 
> > Radim, Cython 0.19.1, SciPy 0.12.0, Python 2.7.1, NumPy & SciPy BLAS 
> from OS 
> > X Accelerate 
> > 
> > 
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