Re: [Boost-users] removing parallel edges in the Boost Graph Library?

31 Mar 2004

      I modified the edge_property.cpp example to demonstrate the problem. I 
added an edge of flow 42 to the graph defined in the file so that there 
are now two edges (3,6) with different capacities. I then loop through 
the graph, and remove any edges that have flow of 42 by calling 
remove_edge(e, G). Since there is only one edge in the graph that has 
flow 42, this calls remove_edge only once. As is evident by the output 
of the program, both edges (3,6) get removed from the graph.

I hope this will help you find the problem.

Thanks,
Nicholas Burlett
nrb23@cornell.edu

On Mar 31, 2004, at 11:26 AM, Jeremy Siek wrote:
...
Hi Nicholas,
That sounds like a bug. Could you post a complete C++ program so I can
immediately reproduce the problem.
Thanks,
Jeremy
On Mar 30, 2004, at 5:26 PM, Nicholas Burlett wrote:
...
I am trying to use BGL to model a directed multigraph, but every time 
I try to remove just one of the edges (u,v), it removes all of the 
edges from u to v.
My graph definition is:
    typedef adjacency_list<listS, listS, bidirectionalS, 
VertexProperty, EdgeProperty> graphdata;
where VertexProperty and EdgeProperty are properties I've defined. 
Everything else seems to work: I have can add parallel edges,  find 
the edge I want to remove based on the EdgeProperty, filter the graph 
for topological sorting, check for existing edges, etc.
In the following, e is of type 
graph_traits<graphdata>::edge_descriptor, and g is the graph of type 
graphdata (defined above):
std::cout << "about to remove edge\n";
        DumpInfo();
        remove_edge(e, g);
        std::cout << "removed edge\n";
        DumpInfo();
Here is some sample output:
about to remove edge
vertex: 0
  out-edges:
  in-edges: (1,0) (1,0)
  adjacent vertices:
vertex: 1
  out-edges: (1,0) (1,0)
  in-edges:
  adjacent vertices: 0 0
removed edge
vertex: 0
  out-edges:
  in-edges:
  adjacent vertices:
vertex: 1
  out-edges:
  in-edges:
  adjacent vertices:
Note that there were two edges present before the call to 
remove_edge, but only one after.
What am I doing wrong?
I'm using version 1.31, if that helps.
Thanks,
Nicholas Burlett
nrb23@cornell.edu
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_______________________________________________
Jeremy Siek <jsiek@osl.iu.edu>
http://www.osl.iu.edu/~jsiek
Ph.D. Student, Indiana University Bloomington
Graduating in August 2004 and looking for work
C++ Booster (http://www.boost.org)
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