Suppose I want to test an algorithm for graph isomorphism check.

Starting from a given graph, I would do a random permutation of vertices to build the second graph.

Is there a way of making another isomorphic graph that is "more difficult" to check?

  • 4
    $\begingroup$ No, because given any labelling of a graph you can make a random labelling of that. So every labelling is equally difficult. That doesn't mean a particular algorithm will take the same time for each labelling. $\endgroup$ Sep 11, 2021 at 14:51
  • 1
    $\begingroup$ Maybe it's more interesting to ask for a non-isomorphic graph that is difficult to check? $\endgroup$ Sep 12, 2021 at 1:38
  • 1
    $\begingroup$ @Gerry Myerson yes, right. $\endgroup$
    – BillyJoe
    Sep 12, 2021 at 6:47


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