Problem in vf2_subgraph_iso handling self-loops when using undirectedS

[Flavio De Lorenzi <fdlorenzi@…>]

The attached example (with 1 vertex and 1 self-loop) illustrates that vf2_subgraph_iso fails to detect the isomorphism when using underictedS and e.g. vecS as edge list. This is because adding a single self-loop to a vertex (when using vecS as edge list) results in 2 out-edges having the same edge descriptor. Is this intended? (In contrast, using setS as edge list to describe the same graph (1 vertex and 1 self-loop) results in only one out-edge. In this case vf2_subgraph_iso finds the isomorphism because each out-edge has a unique edge descriptor).

This affects also previous versions.

Best wishes, Flavio

[Flavio De Lorenzi <fdlorenzi@…>]

example to illustrate the issue