[SciPy-Dev] GSoC 2018: Cythonizing

[Jaime Fernández del Río]

On Wed, Feb 28, 2018 at 3:40 PM Lars G. <lagru at mailbox.org> wrote:

> Dear SciPy devs,
>
> I'm currently thinking about an application for this year's GSoC as
> well. As there already seems to be a large interest in the rotation
> formalism I'm trying to find another area that matches my interest and
> skill.
>
> I've dug up this proposal in scikit-image from GSoC 2015
>
> https://github.com/scikit-image/scikit-image/wiki/GSoC-2015#rewriting-scipyndimage-in-cython
> and judging by the state of scipy/ndimage/src/ nobody has worked on this
> proposal yet (feel free to correct me).
>

I mentored the not very successful, to put it mildly, GSoC 2015 project
about cythonizing ndimage. From that experience, and further work
afterwards, I no longer think Cython is the answer to ndimage's problems.
The underlying C has a lot of very complicated code making lots of clever
(often too clever for everyone's good) uses of pointer magic, that I
honestly think are better kept in C. Or would at least need someone with a
very deep understanding of both C and Cython, would much exceed the scope
of a GSoC project, and I don't think I can commit to properly mentor such a
project this summer.

What would be nice is to replace the current nd_image.c file that
implements the Python interface to the underlying C by a Cython
implementation. That is not enough for a GSoC project, and it's not the
most exciting thing to work on either. But if you want to put a full
project together out of smaller, Cython related, subprojects, this could
certainly be a part of it, and I wouldn't mind mentoring that subproject.

Jaime


> Alternatively I could imagine something similar for other sub-packages,
> e.g. scipy/signal which features many source files in C as well.
>
> So basically if there is an interest I could try to port C / Python code
> to Cython. What I would like to know:
>
> - Is there an interest? ;)
> - Is the original proposal in scikit-image still unfinished and are the
>   potential mentors still interested in mentoring?
> - If there is a general interest to cythonize C or Python code during a
>   GSoC project, which parts / sub-packages of SciPy would you priorize?
>
> As for my current involvement with SciPy:
>
> - I've already added a small function written in Cython
>   https://github.com/scipy/scipy/pull/8350


P.S. Have submitted a small enhancement to your code, could you take a look?

https://github.com/scipy/scipy/pull/8499


> - as part of a larger PR extending the signal module
>   https://github.com/scipy/scipy/pull/8264
>   which will possibly merged this week.
> - I already cythonized slow parts of the above PR and plan
>   to add these with new PRs after #8264 is merged.
>
> If this receives positive feedback I'd be happy to draft a more complete
> proposal / application based on the discussion around this.
>
> Best regards,
> Lars
>
>
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