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
GAP 3.4.4