Is there a software that can enumerate endomorphisms of a given directed graph? The closest thing I found is the graph homomorphism testing in Sage (G.has_homomorphism_to(H)), and I could probably go from there by letting H go over the subgraphs of G and taking into account the number of automorphisms of H. The problem though is that the has_homomorphism_to functionality is available only for undirected graphs. Does there exist any alternative for directed graphs?
Counting endomorphisms of a given directed graph
graphs;graph theory;computer algebra;mathematical software