[Boost-users] Re: BGL + Subgraph + Propertymap issue...

From: Gordon Smith (schmoo2k_at_[hidden])
Date: 2005-02-09 09:17:17

Agreed - Thx for the heads up.

Gordon.

"Douglas Gregor" <dgregor_at_[hidden]> wrote in message
news:AEEDC074-7AA3-11D9-A33F-000D932B7224_at_cs.indiana.edu...
> On Feb 8, 2005, at 5:08 PM, Gordon Smith wrote:
>
> > The following example produces the following (unexpected results):
> > name: graph
> > name: subgraph 1
> > name sg2: subgraph 2
> > name sg: subgraph 2
> >
> > Do subgraphs share the same property_map?
>
> Sometimes.
>
> Vertex and edge properties are *not* shared: each subgraph has a
> separate copy of these internal properties.
> Graph properties *are* shared, as your example proves. The get_property
> code in the subgraph header explicitly references the root of the
> subgraph when accessing graph properties.
>
> Personally, I think this is completely backward. The vertices and edges
> of a (conceptual) subgraph are the same vertices and edges of the graph
> itself, so they should be the same and have the same properties; this
> is the problem that Jeffrey Holle is referring to. But, each subgraph
> is in essence a different graph, so it should have its own graph
> properties; this is the unexpected behavior you've run into.
>
> Doug