On Thu, 15 Jul 2010, Adam Spargo wrote:
There is a subgraph class in BGL, and also filtered_graph. Are the subgraphs you're working with induced subgraphs (i.e., you do not selectively remove edges other than by filtering out their endpoints)? The subgraph class seems to make the subgraphs look more like normal graphs, while filtered_graph is probably much simpler (it doesn't update num_vertices() to match the subgraph size, for example). If you're passing in something like the connected components of a graph individually, that is an induced subgraph and so either of those classes will work directly.
Thanks, I think that it is filtered_graph that I want as the vertex indices are meaningful to me. I've adapted the filtered_graph example to do what I want on a small graph, code attached. Just a couple questions - is finding the components, then copying into a property map the most efficient method, could I have the component algorithm populate the property map directly.
I don't see why you can't just pass get(vertex_component, g) as the component map in connected_components(), rather than using an iterator_property_map. That would accomplish your goal. In terms of the vertex filter, I think you are doing it the right way. I would have thought that there would be a component filter in BGL, but I could not find one. There is a property_map_filter in filtered_graph.hpp, but that does not check an integer value, only a bool.
Second, I could only get this working by adding an edge filter AND a vertex filter, but really I only need a vertex filter, how to pass an 'empty' function object to the constructor?
Look at boost::keep_all (in filtered_graph.hpp); that can be used to keep all of a certain kind of entity. -- Jeremiah Willcock