[pypy-dev] Questions on the pypy+numpy project

David Cournapeau cournape at gmail.com
Tue Oct 18 21:33:00 CEST 2011

On Tue, Oct 18, 2011 at 8:02 PM, Armin Rigo <arigo at tunes.org> wrote:
> Hi David,
> On Tue, Oct 18, 2011 at 18:29, David Cournapeau <cournape at gmail.com> wrote:
>>>> (...) with the possibility to replace it in a PyPy specific way.
>>> I think you are disregarding what 8 years of the PyPy project should
>>> have made obvious. (...)
>> Ok. In that case, it is fair to say that you are talking about a full
>> reimplementation of the whole scipy ecosystem, at least as much as
>> pypy itself is a reimplementation of python  ?
> I think the original topic of this discussion is numpy, not scipy.
> The answer is that I don't know.  I am sure that people will
> reimplement whatever module is needed, or design a generic but slower
> way to interface with C a la cpyext, or write a different C API, or
> rely on Cython versions of their libraries and have Cython support in
> PyPy... or more likely all of these approaches and more.
> The point is that right now we are focusing on numpy only, and we want
> to make existing pure Python numpy programs run fast --- not just run
> horribly slowly ---  both in the case of "standard" numpy programs,
> and in the case of programs that do not strictly follow the mold of
> "take your algorithm, then shuffle it and rewrite it and possibly
> obfuscate it until it is expressed as matrix operations with no
> computation left in pure Python".
> This is the first step for us right now.  It will take some time
> before we have to even consider running scipy programs.  By then I
> imagine that either the approach works and delivers good performance
> --- and then people (us and others) will have to consider the next
> steps to build on top of that --- or it just doesn't (which looks
> unlikely given the good preliminary results, which is why we can ask
> for support via donations).
> We did not draw precise plans for what comes next.  I think the above
> would already be a very useful result for some users.  But to me, it
> looks like a strong enough pull to motivate some more people to do the
> next steps --- Cython, C API, rewrite of some modules, and so on,
> including the perfectly fine opinion "in my case pypy is not giving
> enough benefits for me to care".  Note that this is roughly the same
> issues and same solution spaces as the ones that exist in any domain
> with PyPy, not just numpy/scipy.

Thank you for the clear explanation, Armin, that makes things much
clearer, at least to me.



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