[SciPy-Dev] scipy.io.loadmat and matvec multiply

[Jonathan Taylor]

Thanks for all the help.

That said, I'm not sure it is an issue of the strides. I can easily
recreate the slowdown as in the above gist ( https://gist.github.com/
da7b2ef6ef109511af06a9cebbfc8ed1 ). Also, modifying the flags of a
user-created ndarray so they agree with the loaded one is still noticably
faster than using the array from `scipy.io.loadmat`

For my purposes, a copy is just fine, but I think this might be an issue
that could be looked into. Perhaps I should file an issue on github?

On Sat, Aug 26, 2017 at 11:06 AM, Robert Kern <robert.kern at gmail.com> wrote:

> On Sat, Aug 26, 2017 at 12:09 AM, Jonathan Taylor <
> jonathan.taylor at stanford.edu> wrote:
> >
> > Yes, it's a dense 2500x2000 matrix.
> >
> > Loaded strides: (8, 16000)
> >
> > Copied strides: (20000, 8)
> >
> > So, matvec is just slower because of strides and where numpy retrieves
> data? Is there a simple way to do this besides a copy? I can easily afford
> the copy, just wondering.
>
> It's not simpler, but the most efficient and idiomatic way to ensure
> C-contiguity is to use np.ascontiguousarray(). This will make a copy only
> if necessary.
>
> --
> Robert Kern
>
> _______________________________________________
> SciPy-Dev mailing list
> SciPy-Dev at python.org
> https://mail.python.org/mailman/listinfo/scipy-dev
>
>


-- 
Jonathan Taylor
Dept. of Statistics
Sequoia Hall, 137
390 Serra Mall
Stanford, CA 94305
Tel:   650.723.9230
Fax:   650.725.8977
Web: http://www-stat.stanford.edu/~jtaylo
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/scipy-dev/attachments/20170828/a8e58591/attachment.html>