Revision history [back]

If I understand well your construction in terms of graphs, each time you have arcs (u, v), (v, w) and (u, w), so a transitive tournament on 3 vertices, you remove arc (u, w). This can be done as follows:

def toto(M): 
    D = DiGraph(M - identity_matrix(M.ncols())) 
    A = [] 
    for u, v in D.edges(labels=False): 
        for w in D.neighbor_out_iterator(u): 
            if D.has_edge(v, w): 
                A.append((u, w)) 
    D.delete_edges(A) 
    return D