Thanks for your input!, you definitely know more about such computations than me.
Roland Schulz wrote: > > > On Thu, Jun 11, 2009 at 4:01 PM, Dag Sverre Seljebotn > <da...@student.matnat.uio.no <mailto:da...@student.matnat.uio.no>> wrote: > Right :-) Now linear algebra support in the compiler *would* be taking > things quite overboard (and probably only slow things down, unless N is > really small, like 4x4 3D game matrices...), I'm actually against that. > > > > Well only if you do it directly in a hard-coded datatype. > > Why not having a non numeric base class as Stefan proposed. And then > allowing the operator functions be handled by Eigen/Blitz. This would > enable very fast numerics, including SSE and fast linear algebra. And > without having it as tightly coupled in the main language. Similar in > that expect to weave, but with all the advantages of cython. I'll answer this below. > > Component wise operations without optimization (thus collapsing > d=a*b*c*d into one loop instead of 3 and not using temporary arrays) > does not give you any speed-up over Numpy for vectorized code with large > arrays. > > For vectorized Numpy code the bottleneck is not the call from Python to > C, but the inefficient use of cache because of the temporary arrays. I don't know enough about this, but these two paragraphs seem slightly contradictory to me. Anyway: Any builtin features as such in Cython can't really depend on Eigen/Blitz. (I know this is perhaps not what you are suggesting, but bear with me.) As the CEP 517 says, I see this as a two-step process: 1) Naive C loops produced by Cython, which will be "good enough" for many cases, and which gives a reference spec and implementation which runs out of the box without library requirements. 2) Various plugins (with a seperate release process from Cython so that work in this area doesn't bog down Cython development), using e.g. Eigen/Blitz as backends, or run it on a GPU, in parallell using OpenMP (well, for heavy componentwise functions), etc. etc. Whether a library could be produced in a mixture of C++ and Cython, perhaps adding more Cython features along the way, which implemented this directly using Eigen/Blitz instead... perhaps. It seems more difficult to get the smooth PEP 3118 integration, but it could perhaps be done. > > And I don't think you need a full metalanguage to map the array class to > Eigen/Blitz. Though it would be still be couple somewhat to the main > language otherwise I agree you would need a metalanguage or full > template support. But it seems to me that there should be an optimum > between full template support and doing the numerics directly in a > language specific numeric array type. Sorry for being vage in this > central point. I just don't know the cython details here. Well, the point here is that when you use Eigen/Blitz, what you do is use the metalanguage of C++. Which is much more powerful than anything we're likely to get in Cython. So in some sense you use C++ to do what you cannot do in Cython. -- Dag Sverre _______________________________________________ Cython-dev mailing list Cython-dev@codespeak.net http://codespeak.net/mailman/listinfo/cython-dev
