map_vertex iterates same node multiple times

[anwarmamat]

I am using Persistent.Digraph.ConcreteLabeled for one my applications. map_vertex is visiting the nodes more than one time.

[backtracking]

You're right. If we consider this a bug, this could be fixed by inserting a memo pattern such as

    let module H = Hashtbl.Make(V) in
    let vtable = H.create 1024 in
    let f v = try H.find vtable v
              with Not_found -> let v' = f v in H.add vtable v v'; v' in

in the code of map_vertex (in file blocks.ml).

[backtracking]

In the meantime, you can use such a workaround on your side, by applying the same memo pattern to the function you are passing to map_vertex.
I agree that it would be nicer to have map_vertex doing it, but at least that's an immediate fix if this is blocking for you.

[anwarmamat]

thanks