Re: [Boost-users] BGL graph library biconnected components

Hi Aaron, Thanks for the response. It turns out that I was being a bit dim; I didn't realise that long paths of vertices, e.g. 1--2--3--4--5 turn into lots of biconnected components : it's not something that the previous (non-boost) implementation of biconnected components I used did. Your comments on the code were interesting - is the second parameter to the property map really necessary? I have used lots of property maps and have never used this - have I just been lucky? :) Thanks, Greg On Mon, 19 Mar 2007, Aaron Windsor wrote:

On 3/19/07, Greg Reynolds wrote:

...

Hi,

I have been using "biconnected_components.hpp" for quite a while now. However, I have come across some graphs for which it finds far too many components...

Here is my usage:

////////////////////////////

Graph g;

// initialise g and give edges an index

std::vector< int > vec_bcc_nums( num_edges(g) );

iterator_property_map< std::vector< int >::iterator, property_map::type > mapEdgeComponent( vec_bcc_nums.begin() );

int num = biconnected_components(g, mapEdgeComponent);

///////////////////////////

I'm afraid I can't post an example of the graphs (they are really big and I signed an NDA).

What I would like to know is:

a) Is the code above sensible, is there something subtly wrong with it? b) Has anyone else used the biconnected components code in anger on largish (> 300 vertices) graphs?

Hi Greg,

a) Almost - the iterator_property_map constructor should take a second argument that would be an edge index map in this case - if you're using an interior edge index map, your code would look like:

iterator_property_map< std::vector< int >::iterator, property_map::type > mapEdgeComponent( vec_bcc_nums.begin() , get(edge_index,g));

...and that's assuming that you've initialized the edge index map with distinct values in the range 0..num_edges(g)-1. I would also use graph_traits<Graph>::edges_size_type instead of int as the value type of the vector, but that's a minor point.

b) Yes, I've been using it recently, running a lot of tests on largish graphs (never in anger, though.) I haven't come across any problems yet, although it could just be that my tests are silently failing somehow.

In case the omission of an edge index map above was just a typo, and you're still seeing failures, is there any more information you can give about how you think it's failing, or a sample graph it fails on?

Regards, Aaron _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users