Re: [Boost-users] [BGL] Remove all vertices from graph with zero degree

On 12/15/05, Dmitry Bufistov wrote:

Hi all again!

I would really appreciate any ideas how to implement (subject) efficiently with bearing in mind "Iterator" stability. Graph representation is the following:

typedef adjacency_list< listS, ///

...

Graph;

filtered_graph seems isn't what I need. I would like to right as follow

Graph g; remove_empty_vertices(g); //Now g doesn't contain zero degree vertices

Do you need a vector to store your vertex ? With a vector, you can't remove (or add) vertices without invalidated all your vertex iterators. I suggest you to use a listS or setS for your vertex set. Thus, you can write your remove_empty_vertices function like this: template < class Graph > void remove_empty_vertices(Graph& g) { BGL_FORALL_VERTICES(v, g, Graph) { if (degree (v, g) == 0) remove_vertex (v, g); } } else, I don't see an efficient way to do it. (I think you have to restart the loop when you remove a vertex)

Many thanks in advance,

regards,

There may be a better solution... but choose your vertex set container carefully: http://www.boost.org/libs/graph/doc/adjacency_list.html> In general, if you want your vertex and edge descriptors to be stable (never invalidated) then use listS or setS for the VertexList and OutEdgeList template parameters of adjacency_list. If you are not as concerned about descriptor and iterator stability, and are more concerned about memory consumption and graph traversal speed, use vecS for the VertexList and/or OutEdgeList template parameters. </quote> -- Johan