I am running VF2 in igraph (with python interface) and it seems that the algorithm in igraph does not properly support isomorphism with multiple edges between the same two vertices.
Q = igraph.Graph(directed=True)
G = igraph.Graph(directed=True)
print G.get_subisomorphisms_vf2(Q, edge_color1=[1,2], edge_color2=) # empty
print G.get_subisomorphisms_vf2(Q, edge_color1=[2,1], edge_color2=) # one mapping
Is this a known issue? I have seen a few comments around suggesting to use the multiplicity of edges as labels to include in the match, but based on the above example, this still seems problematic unless I am misinterpreting something. Are there any ongoing plans for vf2 to support multiple edges between the same two nodes?