[igraph] Possible bug in isomorphic()

[John Yeung]

Hi.  I am using igraph for Python 2.4 on Windows.

I've only started using the package, and so far it seems wonderful.
But I have encountered the following anomaly:

>>> import igraph
>>> g=igraph.Graph.Full(5)
>>> h=igraph.Graph.Full(5)
>>> g.isomorphic(h)
True
>>> g=igraph.Graph.Full(4)
>>> h=igraph.Graph.Full(4)
>>> g.isomorphic(h)
False
>>> g=igraph.Graph.Full(3)
>>> h=igraph.Graph.Full(3)
>>> g.isomorphic(h)
False
>>> g=igraph.Graph.Full(2)
>>> h=igraph.Graph.Full(2)
>>> g.isomorphic(h)
True
>>>

The description of the isomorphic() method mentions that it simply
looks up the result for graphs of 3 or 4 nodes.  It would seem that
the lookup isn't working or it hasn't been given the right data.  The
isomorphic_bliss() method returns True for all the cases above (and I
can certainly use that as a workaround for my purposes).

I apologize if this has already been reported.  I tried searching for
"isomorphic" in the mailing list archives and did not find this issue.

John