Re: [igraph] Possible bug in isomorphic()

[Gabor Csardi]

John, thanks, this is a bug, probably in the C layer because 
I get the same from R.

Gabor

On Sun, Apr 27, 2008 at 05:06:22PM -0400, John Yeung wrote:
> 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
> 
> 
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-- 
Csardi Gabor <address@hidden>    UNIL DGM