Re: [Boost-users] [BGL] In what order does out_edge_iterator iterate?

From: Aaron Windsor (aaron.windsor_at_[hidden])
Date: 2007-03-05 20:03:05

On 3/5/07, Shufei Fan <fansf_at_[hidden]> wrote:
> Hi,
> In my application, the order in which edges are retreaved is also important to
> me. So my question is, when I iterate through an vertex's out_edges, do they
> show up in the order in which the edges are inserted, or any other principals
> are used in order of iteration? Example:
>     ......
>     typename graph_traits<Graph>::out_edge_iterator out_i, out_end;
>     typename graph_traits<Graph>::edge_descriptor e;
>     for (tie(out_i, out_end) = out_edges(v, g);
>          out_i != out_end; ++out_i)
>     {
>       e = *out_i;
>       Vertex src = source(e, g), targ = target(e, g);
>       std::cout << "(" << get(vertex_id, src)
>                 << "," << get(vertex_id, targ) << ") ";
>     }
>     ......
> How are these edges ordered in the output? And is it right all those iterators
> iterates in the same principals/order?

Hi Shufei,

The order in which edges/vertices appear when you iterate over them
is undefined - in both the BGL graph concepts
(http://www.boost.org/libs/graph/doc/graph_concepts.html)
and in the graph implementations provided with the BGL (adjacency_list,
adjacency_matrix, etc.)

Regards,
Aaron