// In header: <boost/mpi/graph_communicator.hpp>

struct graph_traits<mpi::graph_communicator> {
  // types
  typedef int                        vertex_descriptor;     
  typedef std::pair< int, int >      edge_descriptor;       
  typedef directed_tag               directed_category;     
  typedef disallow_parallel_edge_tag edge_parallel_category;
  typedef unspecified                out_edge_iterator;     
  typedef int                        degree_size_type;      
  typedef unspecified                adjacency_iterator;    
  typedef counting_iterator< int >   vertex_iterator;       
  typedef int                        vertices_size_type;    
  typedef unspecified                edge_iterator;         
  typedef int                        edges_size_type;       
  // public static functions
  static vertex_descriptor null_vertex();
};