63.65 IsIsomorphicGraph

IsIsomorphicGraph( gamma1, gamma2 )

This boolean function uses the nauty program to test the isomorphism of gamma1 with gamma2. The value true is returned if and only if the graphs are isomorphic (as directed, uncoloured graphs).

This function creates or uses the record component canonicalLabelling of a graph. As noted in Nau90, a canonical labelling given by nauty can depend on the version of nauty (Version~1.7 in GRAPE~2.31), certain parameters of nauty (always set the same by GRAPE~2.31), and the compiler and computer used. If you use the canonicalLabelling component (say by using IsIsomorphicGraph) of a graph stored on a file, then you must be sure that this field was created in the same environment in which you are presently computing. If in doubt, unbind the canonicalLabelling component of the graph before testing isomorphism.

    gap> gamma := JohnsonGraph(7,4);;
    gap> delta := JohnsonGraph(7,3);;
    gap> IsIsomorphicGraph( gamma, delta );
    true 

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GAP 3.4.4
April 1997