File: neighbor_bfs.hpp

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//
//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================
//
#ifndef BOOST_GRAPH_NEIGHBOR_BREADTH_FIRST_SEARCH_HPP
#define BOOST_GRAPH_NEIGHBOR_BREADTH_FIRST_SEARCH_HPP

/*
  Neighbor Breadth First Search
  Like BFS, but traverses in-edges as well as out-edges.
  (for directed graphs only. use normal BFS for undirected graphs)
*/
#include <boost/config.hpp>
#include <boost/ref.hpp>
#include <vector>
#include <boost/pending/queue.hpp>
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/graph_concepts.hpp>
#include <boost/graph/visitors.hpp>
#include <boost/graph/named_function_params.hpp>
#include <boost/concept/assert.hpp>

namespace boost {

  template <class Visitor, class Graph>
  struct NeighborBFSVisitorConcept {
    void constraints() {
      BOOST_CONCEPT_ASSERT(( CopyConstructibleConcept<Visitor> ));
      vis.initialize_vertex(u, g);
      vis.discover_vertex(u, g);
      vis.examine_vertex(u, g);
      vis.examine_out_edge(e, g);
      vis.examine_in_edge(e, g);
      vis.tree_out_edge(e, g);
      vis.tree_in_edge(e, g);
      vis.non_tree_out_edge(e, g);
      vis.non_tree_in_edge(e, g);
      vis.gray_target(e, g);
      vis.black_target(e, g);
      vis.gray_source(e, g);
      vis.black_source(e, g);
      vis.finish_vertex(u, g);
    }
    Visitor vis;
    Graph g;
    typename graph_traits<Graph>::vertex_descriptor u;
    typename graph_traits<Graph>::edge_descriptor e;
  };

  template <class Visitors = null_visitor>
  class neighbor_bfs_visitor {
  public:
    neighbor_bfs_visitor(Visitors vis = Visitors()) : m_vis(vis) { }

    template <class Vertex, class Graph>
    void initialize_vertex(Vertex u, Graph& g) {
      invoke_visitors(m_vis, u, g, on_initialize_vertex());      
    }
    template <class Vertex, class Graph>
    void discover_vertex(Vertex u, Graph& g) {
      invoke_visitors(m_vis, u, g, on_discover_vertex());      
    }
    template <class Vertex, class Graph>
    void examine_vertex(Vertex u, Graph& g) {
      invoke_visitors(m_vis, u, g, on_examine_vertex());
    }
    template <class Edge, class Graph>
    void examine_out_edge(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_examine_edge());
    }
    template <class Edge, class Graph>
    void tree_out_edge(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_tree_edge());      
    }
    template <class Edge, class Graph>
    void non_tree_out_edge(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_non_tree_edge());
    }
    template <class Edge, class Graph>
    void gray_target(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_gray_target());
    }
    template <class Edge, class Graph>
    void black_target(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_black_target());
    }
    template <class Edge, class Graph>
    void examine_in_edge(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_examine_edge());
    }
    template <class Edge, class Graph>
    void tree_in_edge(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_tree_edge());      
    }
    template <class Edge, class Graph>
    void non_tree_in_edge(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_non_tree_edge());
    }
    template <class Edge, class Graph>
    void gray_source(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_gray_target());
    }
    template <class Edge, class Graph>
    void black_source(Edge e, Graph& g) {
      invoke_visitors(m_vis, e, g, on_black_target());
    }
    template <class Vertex, class Graph>
    void finish_vertex(Vertex u, Graph& g) {
      invoke_visitors(m_vis, u, g, on_finish_vertex());      
    }
  protected:
    Visitors m_vis;
  };

  template <class Visitors>
  neighbor_bfs_visitor<Visitors>
  make_neighbor_bfs_visitor(Visitors vis) {
    return neighbor_bfs_visitor<Visitors>(vis);
  }

  namespace detail {

    template <class BidirectionalGraph, class Buffer, class BFSVisitor, 
              class ColorMap>
    void neighbor_bfs_impl
      (const BidirectionalGraph& g, 
       typename graph_traits<BidirectionalGraph>::vertex_descriptor s, 
       Buffer& Q, BFSVisitor vis, ColorMap color)

    {
      BOOST_CONCEPT_ASSERT(( BidirectionalGraphConcept<BidirectionalGraph> ));
      typedef graph_traits<BidirectionalGraph> GTraits;
      typedef typename GTraits::vertex_descriptor Vertex;
      typedef typename GTraits::edge_descriptor Edge;
      BOOST_CONCEPT_ASSERT(( 
        NeighborBFSVisitorConcept<BFSVisitor, BidirectionalGraph> ));
      BOOST_CONCEPT_ASSERT(( ReadWritePropertyMapConcept<ColorMap, Vertex> ));
      typedef typename property_traits<ColorMap>::value_type ColorValue;
      typedef color_traits<ColorValue> Color;
      
      put(color, s, Color::gray());
      vis.discover_vertex(s, g);
      Q.push(s);
      while (! Q.empty()) {
        Vertex u = Q.top();
        Q.pop(); // pop before push to avoid problem if Q is priority_queue.
        vis.examine_vertex(u, g);

        typename GTraits::out_edge_iterator ei, ei_end;
        for (boost::tie(ei, ei_end) = out_edges(u, g); ei != ei_end; ++ei) {
          Edge e = *ei;
          vis.examine_out_edge(e, g);
          Vertex v = target(e, g);
          ColorValue v_color = get(color, v);
          if (v_color == Color::white()) {
            vis.tree_out_edge(e, g);
            put(color, v, Color::gray());
            vis.discover_vertex(v, g);
            Q.push(v);
          } else {
            vis.non_tree_out_edge(e, g);
            if (v_color == Color::gray())
              vis.gray_target(e, g);
            else
              vis.black_target(e, g);
          }
        } // for out-edges

        typename GTraits::in_edge_iterator in_ei, in_ei_end;
        for (boost::tie(in_ei, in_ei_end) = in_edges(u, g); 
             in_ei != in_ei_end; ++in_ei) {
          Edge e = *in_ei;
          vis.examine_in_edge(e, g);
          Vertex v = source(e, g);
          ColorValue v_color = get(color, v);
          if (v_color == Color::white()) {
            vis.tree_in_edge(e, g);
            put(color, v, Color::gray());
            vis.discover_vertex(v, g);
            Q.push(v);
          } else {
            vis.non_tree_in_edge(e, g);
            if (v_color == Color::gray())
              vis.gray_source(e, g);
            else
              vis.black_source(e, g);
          }
        } // for in-edges

        put(color, u, Color::black());
        vis.finish_vertex(u, g);
      } // while
    }

    
    template <class VertexListGraph, class ColorMap, class BFSVisitor,
      class P, class T, class R>
    void neighbor_bfs_helper
      (VertexListGraph& g,
       typename graph_traits<VertexListGraph>::vertex_descriptor s,
       ColorMap color, 
       BFSVisitor vis,
       const bgl_named_params<P, T, R>& params)
    {
      typedef graph_traits<VertexListGraph> Traits;
      // Buffer default
      typedef typename Traits::vertex_descriptor Vertex;
      typedef boost::queue<Vertex> queue_t;
      queue_t Q;
      // Initialization
      typedef typename property_traits<ColorMap>::value_type ColorValue;
      typedef color_traits<ColorValue> Color;
      typename boost::graph_traits<VertexListGraph>::vertex_iterator i, i_end;
      for (boost::tie(i, i_end) = vertices(g); i != i_end; ++i) {
        put(color, *i, Color::white());
        vis.initialize_vertex(*i, g);
      }
      neighbor_bfs_impl
        (g, s, 
         choose_param(get_param(params, buffer_param_t()), boost::ref(Q)).get(),
         vis, color);
    }

    //-------------------------------------------------------------------------
    // Choose between default color and color parameters. Using
    // function dispatching so that we don't require vertex index if
    // the color default is not being used.

    template <class ColorMap>
    struct neighbor_bfs_dispatch {
      template <class VertexListGraph, class P, class T, class R>
      static void apply
      (VertexListGraph& g,
       typename graph_traits<VertexListGraph>::vertex_descriptor s,
       const bgl_named_params<P, T, R>& params,
       ColorMap color)
      {
        neighbor_bfs_helper
          (g, s, color,
           choose_param(get_param(params, graph_visitor),
                        make_neighbor_bfs_visitor(null_visitor())),
           params);
      }
    };

    template <>
    struct neighbor_bfs_dispatch<param_not_found> {
      template <class VertexListGraph, class P, class T, class R>
      static void apply
      (VertexListGraph& g,
       typename graph_traits<VertexListGraph>::vertex_descriptor s,
       const bgl_named_params<P, T, R>& params,
       param_not_found)
      {
        std::vector<default_color_type> color_vec(num_vertices(g));
        null_visitor null_vis;
        
        neighbor_bfs_helper
          (g, s, 
           make_iterator_property_map
           (color_vec.begin(), 
            choose_const_pmap(get_param(params, vertex_index), 
                              g, vertex_index), color_vec[0]),
           choose_param(get_param(params, graph_visitor),
                        make_neighbor_bfs_visitor(null_vis)),
           params);
      }
    };

  } // namespace detail


  // Named Parameter Variant
  template <class VertexListGraph, class P, class T, class R>
  void neighbor_breadth_first_search
    (const VertexListGraph& g,
     typename graph_traits<VertexListGraph>::vertex_descriptor s,
     const bgl_named_params<P, T, R>& params)
  {
    // The graph is passed by *const* reference so that graph adaptors
    // (temporaries) can be passed into this function. However, the
    // graph is not really const since we may write to property maps
    // of the graph.
    VertexListGraph& ng = const_cast<VertexListGraph&>(g);
    typedef typename get_param_type< vertex_color_t, bgl_named_params<P,T,R> >::type C;
    detail::neighbor_bfs_dispatch<C>::apply(ng, s, params, 
                                            get_param(params, vertex_color));
  }


  // This version does not initialize colors, user has to.

  template <class IncidenceGraph, class P, class T, class R>
  void neighbor_breadth_first_visit
    (IncidenceGraph& g,
     typename graph_traits<IncidenceGraph>::vertex_descriptor s,
     const bgl_named_params<P, T, R>& params)
  {
    typedef graph_traits<IncidenceGraph> Traits;
    // Buffer default
    typedef boost::queue<typename Traits::vertex_descriptor> queue_t;
    queue_t Q;

    detail::neighbor_bfs_impl
      (g, s,
       choose_param(get_param(params, buffer_param_t()), boost::ref(Q)).get(),
       choose_param(get_param(params, graph_visitor),
                    make_neighbor_bfs_visitor(null_visitor())),
       choose_pmap(get_param(params, vertex_color), g, vertex_color)
       );
  }

} // namespace boost

#endif // BOOST_GRAPH_NEIGHBOR_BREADTH_FIRST_SEARCH_HPP