[Numpy-discussion] Proposed Roadmap Overview

Charles R Harris charlesr.harris@gmail....
Sat Feb 18 15:55:40 CST 2012


On Sat, Feb 18, 2012 at 2:51 PM, Matthew Brett <matthew.brett@gmail.com>wrote:

> On Sat, Feb 18, 2012 at 1:40 PM, Charles R Harris
> <charlesr.harris@gmail.com> wrote:
> >
> >
> > On Sat, Feb 18, 2012 at 2:17 PM, David Cournapeau <cournape@gmail.com>
> > wrote:
> >>
> >> On Sat, Feb 18, 2012 at 8:45 PM, Charles R Harris
> >> <charlesr.harris@gmail.com> wrote:
> >> >
> >> >
> >> > 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.
> >>
> >> The proposal of moving to a core C + cython has been discussed by
> >> multiple contributors. It is certainly a valid proposal. *I* have
> >> worked on this (npymath, separate compilation), although certainly not
> >> as much as I would have wanted to. I think much can be done in that
> >> vein. Using the "shut up if you don't do it" is a straw man (and
> >> uncalled for).
> >
> >
> > OK, I was annoyed.
>
> By what?
>
>
Exactly.

Chuck
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