[Numpy-discussion] Proposed Roadmap Overview

Matthew Brett matthew.brett@gmail....
Sat Feb 18 14:39:31 CST 2012


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.

Best,

Matthew


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