[Numpy-discussion] Proposed Roadmap Overview

Charles R Harris charlesr.harris@gmail....
Sat Feb 18 14:45:24 CST 2012


On Sat, Feb 18, 2012 at 1:39 PM, Matthew Brett <matthew.brett@gmail.com>wrote:

> Hi,
>
> On Sat, Feb 18, 2012 at 12:35 PM, Charles R Harris
> <charlesr.harris@gmail.com> wrote:
> >
> >
> > On Sat, Feb 18, 2012 at 12:21 PM, Matthew Brett <matthew.brett@gmail.com
> >
> > wrote:
> >>
> >> Hi.
> >>
> >> On Sat, Feb 18, 2012 at 12:18 AM, Christopher Jordan-Squire
> >> <cjordan1@uw.edu> wrote:
> >> > On Fri, Feb 17, 2012 at 11:31 PM, Matthew Brett
> >> > <matthew.brett@gmail.com> wrote:
> >> >> Hi,
> >> >>
> >> >> On Fri, Feb 17, 2012 at 10:18 PM, Christopher Jordan-Squire
> >> >> <cjordan1@uw.edu> wrote:
> >> >>> On Fri, Feb 17, 2012 at 8:30 PM, Sturla Molden <sturla@molden.no>
> >> >>> wrote:
> >> >>>>
> >> >>>>
> >> >>>> Den 18. feb. 2012 kl. 05:01 skrev Jason Grout
> >> >>>> <jason-sage@creativetrax.com>:
> >> >>>>
> >> >>>>> On 2/17/12 9:54 PM, Sturla Molden wrote:
> >> >>>>>> We would have to write a C++ programming tutorial that is based
> on
> >> >>>>>> Pyton knowledge instead of C knowledge.
> >> >>>>>
> >> >>>>> I personally would love such a thing.  It's been a while since I
> did
> >> >>>>> anything nontrivial on my own in C++.
> >> >>>>>
> >> >>>>
> >> >>>> One example: How do we code multiple return values?
> >> >>>>
> >> >>>> In Python:
> >> >>>> - Return a tuple.
> >> >>>>
> >> >>>> In C:
> >> >>>> - Use pointers (evilness)
> >> >>>>
> >> >>>> In C++:
> >> >>>> - Return a std::tuple, as you would in Python.
> >> >>>> - Use references, as you would in Fortran or Pascal.
> >> >>>> - Use pointers, as you would in C.
> >> >>>>
> >> >>>> C++ textbooks always pick the last...
> >> >>>>
> >> >>>> I would show the first and the second method, and perhaps
> >> >>>> intentionally forget the last.
> >> >>>>
> >> >>>> Sturla
> >> >>>>
> >> >>
> >> >>> On the flip side, cython looked pretty...but I didn't get the
> >> >>> performance gains I wanted, and had to spend a lot of time figuring
> >> >>> out if it was cython, needing to add types, buggy support for numpy,
> >> >>> or actually the algorithm.
> >> >>
> >> >> At the time, was the numpy support buggy?  I personally haven't had
> >> >> many problems with Cython and numpy.
> >> >>
> >> >
> >> > It's not that the support WAS buggy, it's that it wasn't clear to me
> >> > what was going on and where my performance bottleneck was. Even after
> >> > microbenchmarking with ipython, using timeit and prun, and using the
> >> > cython code visualization tool. Ultimately I don't think it was
> >> > cython, so perhaps my comment was a bit unfair. But it was
> >> > unfortunately difficult to verify that. Of course, as you say,
> >> > diagnosing and solving such issues would become easier to resolve with
> >> > more cython experience.
> >> >
> >> >>> The C files generated by cython were
> >> >>> enormous and difficult to read. They really weren't meant for human
> >> >>> consumption.
> >> >>
> >> >> Yes, it takes some practice to get used to what Cython will do, and
> >> >> how to optimize the output.
> >> >>
> >> >>> As Sturla has said, regardless of the quality of the
> >> >>> current product, it isn't stable.
> >> >>
> >> >> I've personally found it more or less rock solid.  Could you say what
> >> >> you mean by "it isn't stable"?
> >> >>
> >> >
> >> > I just meant what Sturla said, nothing more:
> >> >
> >> > "Cython is still 0.16, it is still unfinished. We cannot base NumPy on
> >> > an unfinished compiler."
> >>
> >> Y'all mean, it has a zero at the beginning of the version number and
> >> it is still adding new features?  Yes, that is correct, but it seems
> >> more reasonable to me to phrase that as 'active development' rather
> >> than 'unstable', because they take considerable care to be backwards
> >> compatible, have a large automated Cython test suite, and a major
> >> stress-tester in the Sage test suite.
> >>
> >
> > Matthew,
> >
> > No one in their right mind would build a large performance library using
> > Cython, it just isn't the right tool. For what it was designed for -
> > wrapping existing c code or writing small and simple things close to
> Python
> > - it does very well, but it was never designed for making core C/C++
> > libraries and in that role it just gets in the way.
>
> I believe the proposal is to refactor the lowest levels in pure C and
> move the some or most of the library superstructure to Cython.
>

Go for it.

Chuck
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