And once I had performed the multi-source BFS, would these
>> levels correspond to dependency levels given by the topo sort?
>
>
> I don't think so, although you can probably use them for similar purposes.

Thanks for the help so far.  This is quite close, bit not quite the right answer.  I need the distance at each vertex to be the max of the distance of its predecessors.  This requires all source vertices from in-edges to be visited before the target vertex.

Is there another construction in bgl that will automatically give that visitation order?

Thanks. 
  Brian