Memory error prevention in itertools.permutation

Question

Firstly, I would like to mention that I have a 3 GB drum.

I am working on an algorithm that is exponential in time on nodes, so for it I have in code

perm = list( itertools.permutations(list(graph.Nodes))) # graph.Nodes is a tuple of 1 , 2 , ... n integers

which generates all the combinations of vertices in the list, and then I can work on one of the permutations.

However, when I run the program for 40 vertices, it gives a memory error.

Is there an easier way in the implementation through which I can generate all combinations of vertices and not have this error.

+5

user506710 Jun 28 '11 at 8:01

2 answers

+4

Robin 28 . '11 8:16

Cédric Julien · Accepted Answer · 2011-06-28T08:06:35+0000

Try using an iterator generated by permutations instead of recreating a list with it:

perm_iterator = itertools.permutations(list(graph.Nodes))

for item in perm_iterator:
   do_the_stuff(item)

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