AutGroupGraph( gamma )
AutGroupGraph( gamma, colouring )
The first version of this function returns the automorphism group of the (directed) graph gamma, using nauty.
In the second version, colouring is a vertex-colouring of gamma, and the subgroup of Aut(<gamma>) preserving this colouring is returned. Here, a colouring should be given as a list of sets, forming a partion of the vertices. The set for the last colour may be omitted. Note that we do not require that adjacent vertices have different colours.
gap> gamma := JohnsonGraph(4,2);; gap> Size(AutGroupGraph(gamma)); 48 gap> Size(AutGroupGraph(gamma,[[1,6]])); 16
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