On Tue, Feb 14, 2012 at 9:11 AM, Pierre <pierre.guil...@gmail.com> wrote: > Hey, thanks for all the responses. I use Cython occasionally, but i > tend to restrict myself to basic C types and simple functions which do > not import anything -- it seems I can learn an awful lot by studying > your examples! > > Can i ask the following questions about Jason's code? > > ** why so you 'import' CDF while you 'cimport' ComplexDoubleElement? > what is the difference?
cimport gives access to the underlying C-level data structure. > ** and why do these imports anyway, are they necessary for "cdef > complex..." to work? Nope! If you just want to use Python's complex data type you could rewrite the code to not use any imports. > ** I didn't know PY_NEW. What is the difference between res= > PY_NEW(Matrix2) and simply res= Matrix2(0,0,0,0) (say) ? and what > about using PY_NEW with a class that *requires* parameters to its > __init__? PY_NEW is a macro that creates the class without calling __init__. This is an optimization. > ** more generally, is there a Cython tutorial that would be (just) > sufficiently advanced to cover such an example? You may find chapter 3 of this book I'm writing helpful: http://wstein.org/books/sagebook/sagebook.pdf > > thanks! > Pierre > > On 13 fév, 20:13, William Stein <wst...@gmail.com> wrote: >> On Mon, Feb 13, 2012 at 11:07 AM, Jason Grout >> >> >> >> >> >> >> >> >> >> <jason-s...@creativetrax.com> wrote: >> > On 2/13/12 12:41 PM, William Stein wrote: >> >> >> On Mon, Feb 13, 2012 at 10:29 AM, Robert Bradshaw >> >> <rober...@math.washington.edu> wrote: >> >> >>> On Mon, Feb 13, 2012 at 10:06 AM, William Stein<wst...@gmail.com> wrote: >> >> >>>> On Mon, Feb 13, 2012 at 9:59 AM, Pierre<pierre.guil...@gmail.com> >> >>>> wrote: >> >> >>>>> I see. Well I *do* have hundreds of 2x2 matrices to multiply out so >> >>>>> i'm better off storing them as numpy matrices throughout... thanks for >> >>>>> your explanations though. >> >> >>>>> Pierre >> >> >>>> You might consider using Cython and writing a custom 2x2 matrix class. >> >>>> It wouldn't be difficult... so I'll write one right now and respond >> >>>> with the benchmarks. >> >> >> Here it is: http://480.sagenb.org/home/pub/97/ >> >> >> I ended up using GSL's complex matrix data type and the BLAS level 3 >> >> routine to do the multiplication. I did not add any other >> >> convenience functions to the class, so some more will probably be >> >> needed for your application. >> >> > I'm curious why you didn't just store the 4 complex numbers in C. >> >> I was concerned about "numerical stability" and figured BLAS would >> deal with that. But maybe that doesn't matter. >> >> Most importantly, I forgot about Cython's complex type, which I now >> remember Robert Bradshaw wrote for his thesis work. I wasn't looking >> forward to writing your line: >> >> res.m00=self.m00*right.m00+self.m01*right.m10 >> >> but against the gsl library. But using the cython type in complex, >> you get the above at C speed with easy notation, which is pretty >> awesome. >> >> > I tried >> > it and got a much bigger speedup: 17x faster than numpy and 150x faster >> > than >> > Sage. Seehttp://sagenb.org/home/pub/4303/ >> >> Nice. >> >> >> >> > Thanks, >> >> > Jason >> >> > -- >> > To post to this group, send email to sage-support@googlegroups.com >> > To unsubscribe from this group, send email to >> > sage-support+unsubscr...@googlegroups.com >> > For more options, visit this group at >> >http://groups.google.com/group/sage-support >> > URL:http://www.sagemath.org >> >> -- >> William Stein >> Professor of Mathematics >> University of Washingtonhttp://wstein.org > > -- > To post to this group, send email to sage-support@googlegroups.com > To unsubscribe from this group, send email to > sage-support+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/sage-support > URL: http://www.sagemath.org -- William Stein Professor of Mathematics University of Washington http://wstein.org -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
