On Sat, Feb 18, 2012 at 1:39 PM, Matthew Brett <matthew.br...@gmail.com>wrote:
> Hi, > > On Sat, Feb 18, 2012 at 12:35 PM, Charles R Harris > <charlesr.har...@gmail.com> wrote: > > > > > > On Sat, Feb 18, 2012 at 12:21 PM, Matthew Brett <matthew.br...@gmail.com > > > > wrote: > >> > >> Hi. > >> > >> On Sat, Feb 18, 2012 at 12:18 AM, Christopher Jordan-Squire > >> <cjord...@uw.edu> wrote: > >> > On Fri, Feb 17, 2012 at 11:31 PM, Matthew Brett > >> > <matthew.br...@gmail.com> wrote: > >> >> Hi, > >> >> > >> >> On Fri, Feb 17, 2012 at 10:18 PM, Christopher Jordan-Squire > >> >> <cjord...@uw.edu> wrote: > >> >>> On Fri, Feb 17, 2012 at 8:30 PM, Sturla Molden <stu...@molden.no> > >> >>> wrote: > >> >>>> > >> >>>> > >> >>>> Den 18. feb. 2012 kl. 05:01 skrev Jason Grout > >> >>>> <jason-s...@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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