On 9/21/07, Gary Ruben <[EMAIL PROTECTED]> wrote: > > Gael Varoquaux wrote: > > On Fri, Sep 21, 2007 at 02:58:43PM -0600, Charles R Harris wrote: > >> I found generators a good approach to this sort of thing: > > > >> for (i,j,k) in triplets(n) : > > > > That's what we where doing so far, but in the code itself. The result > was > > unbearably slow. > > I think for our purposes we should build a precalculated table of these > > nuplets, and then do array calculations on them. > > I'm not sure whether this helps, but I have found this generator-based > recipe <http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/190465> > very useful in the past. The comment "If you require the complete list > of permutations, just use the built-in list() operator" may apply to > your situation,
Not bad for the triplets, I would have thought the cost of recursion would be greater. The use of lists slows it down a bit for bigger combinations. In [50]: time for i in xuniqueCombinations(range(100),3) : pass CPU times: user 0.56 s, sys: 0.02 s, total: 0.58 s Wall time: 0.57 In [51]: time for i in xuniqueCombinations(range(20),10) : pass CPU times: user 2.17 s, sys: 0.07 s, total: 2.23 s Wall time: 2.23 In [52]: time for i in combination(20,10) : pass CPU times: user 0.96 s, sys: 0.01 s, total: 0.97 s Wall time: 0.97 Chuck
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