[SciPy-user] Low-level code integration discussion at scipy'03?

Robert Ferrell scipy-user@scipy.net
Wed, 3 Sep 2003 14:49:06 -0000 (GMT)


I am very interested in such a discussion.  I won't have much to
contribute, but I'd like to learn.

-robert

<quote who="Fernando Perez">
> Hi everyone,
>
> as I mentioned before, I think it would be great to have a bit of an
> open  discussion on methods and techniques for plugging low-level code
> into python  at Scipy'03.  I don't mean to teach people how to write an
> extension module,  but rather what the best/easiest approaches are for
> writing time-critical code  which manipulates Numpy/numarray arrays.
>
> A brief summary of the alternatives:
>
> * Scipy's weave relies on blitz, which is extremely nice and maps
> surprisingly  well to python arrays.  Blitz arrays have slices, ranges,
> overloaded  arithmetic operators and math functions, etc.  In fact,
> writing blitz C++  feels almost like writing python code, with the
> caveats of handling  compile-time type information.
>
> But blitz development seems to be rather slow these days, and the issue
> of  access to Blas/lapack from blitz isn't fully settled (i.e., it's not
>  out-of-the box easy).
>
> * The ublas library
> (http://www.boost.org/libs/numeric/ublas/doc/overview.htm).  It has
> direct  blas support, but it seems to focus strictly on vectors and
> matrices, and as  far as I see it doesn't support higher rank objects (I
> could be wrong, though:
>   I've been using blitz for 'real' and only looked at the ublas
> webpage).
>
> * Writing low-level code in fortran and using Pearu's f2py.  I love
> f2py, but  I'd prefer my low-level code to have the ability to also use
> more information  from the python side of things if needed.  I think
> f2py is a great tool for  wrapping existing fortran codes, but not so
> much for extending a python  program with a few low-level routines.
> And there is always the potential  need for transposition operations
> when going to Fortran because of the  row/column memory ordering
> discrepancy between C and Fortran.
>
> * Complete roll-your-own solutions using the Numarray C api.  This is
> doable,  but after using blitz arrays, it feels really low-level.  Call
> me lazy, but  after using python I've become fully enamored of writing
> code which reads as  cleanly as possible.
>
>
> What I'd like to know is if there is any interest in organizing a bit of
> a  discussion on this.  If an hour can be squeezed in for this in the
> schedule,  great (and I volunteer to moderate if nobody else wants to).
> If not, perhaps  some of people involved with these topics (Eric,
> Travis, Konrad, Todd and  Perry at least, plus whoever else is
> interested) might be willing to commit to  a lunch/dinner to be spent
> talking about this.
>
> It would be nice to know something in advance, because one of blitz's
> current  developers (Julian Cummings) is at Caltech.  Perhaps we could
> ask him to come  in and answer some questions about Blitz's future.
> Blitz feels like the  lowest-impedance fit to python's semantics, but
> I'd like to know more about  its long-term feasibility before committing
> to use it too much.  If we set any  kind of schedule for this
> discussion, I can try to contact Julian.
>
> Regards,
>
> Fernando.
>
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