[Boost-users] A boost.graph edge problem

From: Jeffrey Holle (jeff.holle_at_[hidden])
Date: 2004-09-21 21:14:21

I'm using boost 1.31.0 and gcc 3.4.2.

While this problem is more of an application code problem, since I got 
no help on other lists, I trying this one with hopes of a response.

I need to identify parallel edges from my graph, which is defined as:
  typedef subgraph<adjacency_list<vecS,
                                  vecS,
                                  bidirectionalS,
    property<vertex_index_t,int,VertexProperty>,
                                 EdgeProperty> > DataGraphT;
typedef boost::graph_traits <DataGraphT>::edge_descriptor DataEdge;

In the test case that I'm working on, I know I have parallel edges, 
actually 4 sets of 3.

I'd like to use this code:
DataGraph::handleParallelEdges(void)
{
   typedef multiset<DataEdge,ltSubgraph> Edges;
   Edges edges;
   graph_traits<DataGraphT>::edge_iterator ei,ei_end;
   for (tie(ei,ei_end)=boost::edges(dataGraph_);ei!=ei_end;++ei)
           edges.insert(*ei);
   for (Edges::const_iterator iter = edges.begin(); iter != edges.end();
     advance(iter,edges.count(*iter)))
     if (edges.count(*iter)>1)
       cout << "See duplicate" << endl;
}

However, when count never returns.
The likely cause of this (I suspect) is the ltSubgraph functor.
Its definition is:

struct ltSubgraph : public std::binary_function<DataEdge,DataEdge,bool>
{
   bool operator() (const DataEdge& s1, const DataEdge& s2) const
   {
     return s1.m_source < s2.m_source ||
      (!(s1.m_source < s2.m_source) && s1.m_target < s2.m_target);
   }
};

I say this because I can see that this functor is being continuously 
called in this infinite loop.

Note that I use this functor in multiple other cases, but not with an 
associate container that allows duplicate keys.

Is there a problem with this code?