Hi, On Tuesday, 14. September 2010 16:56:42 Adam Spargo wrote:

Hi, Just a simple question - if I have a filtered_graph fg, based on adjacency_list g, do changes to g automagically turn up in fg? Or do I need to make a new fg, once I have finished changing g?

AFAIK, a filtered graph is, broadly speaking, just some sort of "mask" that get's laid over the original graph. By "mask" I mean that if you want to access a vertex, it first checks if this vertex should be visible and if so, you can access that vertex in the filtered graph, otherwise not. In that sense, changes on the original graph will also be in the filtered graph. However, you need to take care, that your filter is also valid for the changed original graph. I ran into such a problem. The filter had an attribute that was used to check if a vertex should be visible, but that attribute was not updated properly on changing the original graph.That caused me quite some trouble in finding the issue because everything looked correct to me. I have for example a program that is searching for all the triangles in a graph (Chiba&Nichizeki [1985]). During the execution of the algorithm, the nodes in the original graph get marked. The filtered graph then is used to display only the nodes that are _not_marked, or marked, I don't remember exactly ATM, sorry. In the first approach, the attribute of the filter was the original graph, more precisely, a copy of it. So the changes were not visible for the filter. I then had to recreate the filtered graph again after each change. But then I came along the idea to use a reference to the original graph and that eliminated the need to recreate the filtered graph each time. This should just give you the general idea and is likely to be way off from being efficient or such.

I know I could write a simple test to find out, which I am doing, but I'd be grateful if someone with more experience of BGL could let me know of any exceptions or potential pitfalls.

Unfortunately, I can't help you on this one and I am also interested in answers to this. I did not experience such things until now, except for what I wrote above.

Thanks in advance,

Adam.

-- Dr Adam Spargo High Performance Assembly Group email: aws@sanger.ac.uk Wellcome Trust Sanger Institute Tel: +44 (0)1223 834244 x7728 Hinxton, Cambridge CB10 1SA Fax: +44 (0)1223 494919

Hope this helps. Best, Cedric