Re: [Boost-users] BGL: subgraph adaptor

From: Doug Gregor (dgregor_at_[hidden])
Date: 2005-04-22 17:08:45

On Apr 6, 2005, at 12:31 AM, Elvanör wrote:

> Hello.
>
> I have just been looking recently at the subgraph feature of the BGL. 
> If I understand correctly, in order to use it you *must* first create 
> a root subgraph; you can't use an existing Graph as the root and call 
> create_subgraph on that adjacency_list, for example.
>
> It also seems like when you create a subgraph, it is somehow stored on 
> the root subgraph, since create_subgraph() has a return type of 
> subgraph<Graph>&.
>
> As it returns a reference, I assume that the actual object is somehow 
> stored on the root. But I need to create and delete lots of subgraphs 
> on a given root graph. Creating the subgraph is no problem; however 
> how can I deleted them ??? I could just leave them, of course, but 
> that's an obvious waste of resources...

The subgraph is stored on the root, so that when edges are 
added/removed anywhere in the graph the changes can ripple throughout 
the graph structure. However, there's no support for deleting 
subgraphs.

> Is there an answer to my question? If possible, I'd also like to learn 
> a little bit more about the subgraph implementation (all I can suppose 
> from the documentation is that it is stored in some kind of tree 
> data-strucutre).

The only good answers are in the implementation itself :)

        Doug