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

[CJ Carey]

I tried reproducing the results from your gist using scipy 0.19.0, and I
found that Xmat is aligned after loadmat:

In [3]: Xmat = sio.loadmat('data.mat')['X']

In [4]: Xmat.flags
Out[4]:
  C_CONTIGUOUS : False
  F_CONTIGUOUS : True
  OWNDATA : False
  WRITEABLE : True
  ALIGNED : True
  UPDATEIFCOPY : False

On Mon, Aug 28, 2017 at 1:26 PM, Robert Kern <robert.kern at gmail.com> wrote:

> On Mon, Aug 28, 2017 at 10:13 AM, Jonathan Taylor <
> jonathan.taylor at stanford.edu> wrote:
> >
> > 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`
>
> Ah yeah, if the data is aligned, then that might end up faster. Your
> optimized BLAS will be able to use certain CPU instructions that require
> aligned data. Setting the ALIGNED flag to false won't actually make the
> data unaligned; your BLAS checks the data itself, not the numpy flag.
>
> > 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?
>
> It might be worth checking if scipy.io.loadmat() can be made to ensure
> that it always creates aligned arrays. There isn't anything to be done
> about .dot(), though.
>
> --
> Robert Kern
>
> _______________________________________________
> SciPy-Dev mailing list
> SciPy-Dev at python.org
> https://mail.python.org/mailman/listinfo/scipy-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/scipy-dev/attachments/20170828/e5734a50/attachment-0001.html>