[igraph] Different results from fastgreedy.community on different systems

[Franz]

Hello everybody,

I am doing some research on networks and I find that fastgreedy.community returns different results when run on different PC.

For example, for the SAME network and running the SAME script, I found:

1) 8 communities in an Acer Aspire notebook with an Intel Pentium Processor T4200 running Ubuntu 12.04.
2) 7 communities in an HP Pro Book 6560b with Intel Core i5 running Ubuntu 12.10.  

Modularity is differ

And I have a more significative differences (even 6 communities of difference for the same script depending on the system they are running).

Is it possibile to have such differences depending on the system the script are running on?

Thank you for your help :) 

Best regards

Franz