[Numpy-discussion] Extracting all the possible combinations of a grid

[Charles R Harris]

On 9/21/07, Gael Varoquaux <gael.varoquaux at normalesup.org> wrote:
>
> On Fri, Sep 21, 2007 at 02:33:42PM -0600, Charles R Harris wrote:
> >    I wrote up some of the combinatorial algorithms in python a few years
> ago
> >    for my own use in writing a paper, ( Harris, C. R. Solution of the
> >    aliasing and least squares problems of spaced antenna interferometric
> >    measurements using lattice methods, Radio Sci. 38, 2003). I even
> thought I
> >    had found an error and have a letter from Knuth pointing out that I
> was
> >    mistaken ;) Anyway, there are a lot of neat things in volume 4 and it
> is
> >    well worth the read.
>
> It is. I did my homework, and now I understand why you point this out.
> Basically array programming is really not suited for these kind of
> things. The problem with my solution is that is blows up the memory
> really quickly. It is actually a pretty poor solution. It is obvious when
> you think about this a bit that the problem diverges really quickly if
> you try the brute force approach. It is actually really quick, until it
> blows the memory.


I found generators a good approach to this  sort of thing:

for (i,j,k) in triplets(n) :

Chuck
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