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

From: Douglas Gregor (dgregor_at_[hidden])
Date: 2005-02-09 09:05:41

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