I was recently experimenting with iterators over permutations, and using them to find if a graph was Hamiltonian. This was done by brute force - no clever tricks - simply by trying every possible permutation of vertices and seeing if each was a cycle.
Now there seem to be (at least) two ways of iteration over permutations: v=Permutations(range(n)) vp=v.first() ...more code here... for i in range(factorial(n)): vp=v.next(vp) and v=(p for p in Permutations(range(n))) ...more code here... for i in range(factorial(n)): vp=v.next() Now the second is much much faster than the first. On my rather elderly laptop, with n=7, the second code takes less then 3 seconds, and the first code takes nearly 82 seconds! But here's the thing: when I tried to compile my function (as a spyx file), there was an error converting Pyrex to C when using the second iteration; I was stuck with the slower first method (and importing Permutations from sage.combinat.permutation). So how can I obtain a fast iteration over permutations in compiled code? Thanks, Alasdair --~--~---------~--~----~------------~-------~--~----~ 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 URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
