[Boost-users] BGL:add vertex and edge to subgraph

Subject: [Boost-users] BGL:add vertex and edge to subgraph
From: Alice.gugu (alice.gugu_at_[hidden])
Date: 2009-04-20 01:39:32

Hi, 

I want to generate a local spanning tree of one graph(not MST) so I construct a subgraph of the original graph by add_vertex() and add_edge() function. 
The problem is that after the add_vertex(). the local tree generate edges between the vertexes automaticlly. If I call add_edge() again, it will dumplicat edges since all the edges between existing vertex have been added by add_vertex() function.

I checked the example code of how to add vertex and edge in subgraph.  It seems the add_vertex() function should not add edges automaticlly.

SUBGRAPH m_g;

...
//Create spanning tree
SUBGRAPH& localTree = m_g.create_subgraph();

//Add one vertex as root in spanning tree
boost::add_vertex(m_root, localTree);

//Add descendants to the tree
 typedef graph_traits<SUBGRAPH> GTraits;
 GTraits::out_edge_iterator tmpei, tmpei_end;
 std::pair<GTraits::out_edge_iterator, GTraits::out_edge_iterator> p;
 p = out_edges(m_root, m_g);
 tmpei = p.first;
 tmpei_end = p.second;

 while ( tmpei != tmpei_end ) 
 {
  //Descendant
  PolyGraphVertex tmpv = target(*tmpei , m_g);

  //Add descendant
  boost::add_vertex(tmpv, localTree);

  //Add an edge from ancestor to descendant
  boost::add_edge(m_root,tmpv,localTree);
  tmpei++;
 }