Re: [Boost-users] Graph Isomorphism

On Thu, 23 Jun 2011, Evan Driscoll wrote:

OK, I have a somewhat unrelated question. (I think I can modify the Boost algorithm to do what I want.)

In libs/graph/example/isomorphism.hpp, if I change undirectedS to bidirectionalS, then the answer changes from the two graphs being isomorphic to not. (It then proceeds to segfault when looking at the isomorphism map.)

typedef adjacency_list > graph_t; to typedef adjacency_list > graph_t;

Why is this?

Near as I can tell, the graphs should be isomorphic. Graph 1 has three cycles, 0->1->2->0, 3->4->5->6->3, and 7->8->9->10->11->7. Graph 2 has three cycles of the same sizes, 9->10->11->9, 0->1->3->2->0, and 4->5->7->8->6->4. (These are all the transitions.)

They are not isomorphic as directed graphs: the first component in g1 is 0->1, 1->2, 0->2 (acyclic), while the first component in g2 is 9->10, 10->11, 11->9 (a cycle). The other components are isomorphic in the way that you show. -- Jeremiah Willcock