with regards to replacing weave, would it be possible to just use a
function decorator?
i.e something like:
@cythonize
def trivial_func(int i):
cdef int j
j = i + 1
return j
I particularly like the thought of this over weave so that I don't
have to "switch gears" in brain from reading python to reading C.
Cheers,
Chris
On Tue, Aug 25, 2009 at 5:21 PM, Fernando Perez<[email protected]> wrote:
> Hi folks,
>
> On Tue, Aug 25, 2009 at 12:08 PM, Kurt Smith<[email protected]> wrote:
>> Weave-like support in Cython -- Fernando Perez (not at the BoF)
>> suggested that Cython could assume the same functionality of
>> scipy.weave (see: http://www.scipy.org/Weave), since scipy.weave is
>> poorly documented and could use more maintenance than it is currently
>> getting. I'm personally very interested in this -- it seems that
>> there is much overlap between scipy.weave and the combination of
>> pyximport & the pure-python mode of Cython. It seems that with a bit
>> of work from an interested user and some guidance from yours truly, we
>> could improve pyximport & Cython's pure-python mode to incorporate the
>> good stuff from scipy.weave, but better ;-) I intend to write-up a
>> CEP with my thoughts sometime in the near future.
>>
>
> Kurt, thanks for resurrecting this comment. Indeed, weave is an
> extremely useful piece of functionality but one that has been somewhat
> neglected for years. There's a lot of good in there though, and the
> need for it is significant. It's *really* cool to do things like:
>
> def prod(m, v):
> """Matrix-vector multiply via weave/blitz++"""
> nrows, ncolumns = m.shape
> assert v.ndim==1 and ncolumns==v.shape[0],"Shape mismatch in prod"
>
> res = np.zeros(nrows, float)
> code = r"""
> for (int i=0; i<nrows; i++)
> {
> for (int j=0; j<ncolumns; j++)
> {
> res(i) += m(i,j)*v(j);
> }
> }
> """
> err = inline(code,['nrows', 'ncolumns', 'res', 'm', 'v'], verbose=2,
> type_converters=converters.blitz)
> return res
>
> This makes interactive experimentation and the writing of
> loop/indexing-intensive code really easy. But by itself, weave is in
> serious danger of bitrot, and right now Cython has the momentum and
> concentrated effort for this problem domain.
>
> Everyone is extremely impressed with the amazing work you've all done,
> and rooting for cython to continue to improve, as you are solving a
> number of key problems to make python a really complete platform for
> scientific computing. It's been lots of fun to see cython steadily
> attack a number of problems that have been a real issue for years.
>
> So if Cython absorbs/extends/integrates/develops/whatever the good
> ideas and code from weave, so that this type of workflow is also
> supported, it would be great. I am really happy to see f2py grow
> into fwrap, and the weave machinery (or at least parts of it) seems
> like a logical addition to the cython-based toolkit.
>
> One particular use case for which weave.inline was invaluable to me in
> the past was the generation of fast looping code for various
> dimensions. I had to write function evaluation codes where the user
> could supply a C expression (as a string, that would #define NDIM to
> indicate the dimensionality of the problem). I could then easily
> generate a few methods for D=1..6 (the range I needed to cover) that
> would do certain key operations very fast. The bulk of the code used
> numpy arrays to be dimension agnostic, but a few methods really needed
> explicit loops and with weave, it was made completely transparent to
> the user, all of it being done at runtime (for us, needing gcc at
> runtime was OK). I mention this to give you some feedback on the use
> cases for weave (there are others), but I hope that in the end, all of
> this class of functionality will be available through a unified entry
> point, and if that's cython, all the better.
>
> Thanks again to the team for your great work!
>
> Cheers,
>
> f
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>
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