williamr@2: //=======================================================================
williamr@2: // Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
williamr@2: // Copyright 2004, 2005 Trustees of Indiana University
williamr@2: // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek,
williamr@2: //          Doug Gregor, D. Kevin McGrath
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: //=======================================================================
williamr@2: #ifndef BOOST_GRAPH_CUTHILL_MCKEE_HPP
williamr@2: #define BOOST_GRAPH_CUTHILL_MCKEE_HPP
williamr@2: 
williamr@2: #include <boost/config.hpp>
williamr@2: #include <boost/graph/detail/sparse_ordering.hpp>
williamr@2: #include <algorithm>
williamr@2: 
williamr@2: 
williamr@2: /*
williamr@2:   (Reverse) Cuthill-McKee Algorithm for matrix reordering
williamr@2: */
williamr@2: 
williamr@2: namespace boost {
williamr@2: 
williamr@2:   namespace detail {
williamr@2: 
williamr@2: 
williamr@2: 
williamr@2:     template < typename OutputIterator, typename Buffer, typename DegreeMap > 
williamr@2:     class bfs_rcm_visitor:public default_bfs_visitor
williamr@2:     {
williamr@2:     public:
williamr@2:       bfs_rcm_visitor(OutputIterator *iter, Buffer *b, DegreeMap deg): 
williamr@2:         permutation(iter), Qptr(b), degree(deg) { }
williamr@2:       template <class Vertex, class Graph>
williamr@2:       void examine_vertex(Vertex u, Graph&) {
williamr@2:         *(*permutation)++ = u;
williamr@2:         index_begin = Qptr->size();
williamr@2:       }
williamr@2:       template <class Vertex, class Graph>
williamr@2:       void finish_vertex(Vertex, Graph&) {
williamr@2:         using std::sort;
williamr@2: 
williamr@2:         typedef typename property_traits<DegreeMap>::value_type ds_type;
williamr@2: 
williamr@2:         typedef indirect_cmp<DegreeMap, std::less<ds_type> > Compare;
williamr@2:         Compare comp(degree);
williamr@2:                 
williamr@2:         sort(Qptr->begin()+index_begin, Qptr->end(), comp);
williamr@2:       }
williamr@2:     protected:
williamr@2:       OutputIterator *permutation;
williamr@2:       int index_begin;
williamr@2:       Buffer *Qptr;
williamr@2:       DegreeMap degree;
williamr@2:     };
williamr@2: 
williamr@2:   } // namespace detail  
williamr@2: 
williamr@2: 
williamr@2:   // Reverse Cuthill-McKee algorithm with a given starting Vertex.
williamr@2:   //
williamr@2:   // If user provides a reverse iterator, this will be a reverse-cuthill-mckee
williamr@2:   // algorithm, otherwise it will be a standard CM algorithm
williamr@2: 
williamr@2:   template <class Graph, class OutputIterator,
williamr@2:             class ColorMap, class DegreeMap>
williamr@2:   OutputIterator
williamr@2:   cuthill_mckee_ordering(const Graph& g,
williamr@2:                          std::deque< typename
williamr@2:                          graph_traits<Graph>::vertex_descriptor > vertex_queue,
williamr@2:                          OutputIterator permutation, 
williamr@2:                          ColorMap color, DegreeMap degree)
williamr@2:   {
williamr@2: 
williamr@2:     //create queue, visitor...don't forget namespaces!
williamr@2:     typedef typename property_traits<DegreeMap>::value_type ds_type;
williamr@2:     typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
williamr@2:     typedef typename boost::sparse::sparse_ordering_queue<Vertex> queue;
williamr@2:     typedef typename detail::bfs_rcm_visitor<OutputIterator, queue, DegreeMap> Visitor;
williamr@2:     typedef typename property_traits<ColorMap>::value_type ColorValue;
williamr@2:     typedef color_traits<ColorValue> Color;
williamr@2: 
williamr@2: 
williamr@2:     queue Q;
williamr@2: 
williamr@2:     //create a bfs_rcm_visitor as defined above
williamr@2:     Visitor     vis(&permutation, &Q, degree);
williamr@2: 
williamr@2:     typename graph_traits<Graph>::vertex_iterator ui, ui_end;    
williamr@2: 
williamr@2:     // Copy degree to pseudo_degree
williamr@2:     // initialize the color map
williamr@2:     for (tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui){
williamr@2:       put(color, *ui, Color::white());
williamr@2:     }
williamr@2: 
williamr@2: 
williamr@2:     while( !vertex_queue.empty() ) {
williamr@2:       Vertex s = vertex_queue.front();
williamr@2:       vertex_queue.pop_front();
williamr@2:       
williamr@2:       //call BFS with visitor
williamr@2:       breadth_first_visit(g, s, Q, vis, color);
williamr@2:     }
williamr@2:     return permutation;
williamr@2:   }
williamr@2:     
williamr@2: 
williamr@2:   // This is the case where only a single starting vertex is supplied.
williamr@2:   template <class Graph, class OutputIterator,
williamr@2:             class ColorMap, class DegreeMap>
williamr@2:   OutputIterator
williamr@2:   cuthill_mckee_ordering(const Graph& g,
williamr@2:                          typename graph_traits<Graph>::vertex_descriptor s,
williamr@2:                          OutputIterator permutation, 
williamr@2:                          ColorMap color, DegreeMap degree)
williamr@2:   {
williamr@2: 
williamr@2:     std::deque< typename graph_traits<Graph>::vertex_descriptor > vertex_queue;
williamr@2:     vertex_queue.push_front( s );
williamr@2: 
williamr@2:     return cuthill_mckee_ordering(g, vertex_queue, permutation, color, degree);
williamr@2:   
williamr@2:   }
williamr@2:   
williamr@2: 
williamr@2:   // This is the version of CM which selects its own starting vertex
williamr@2:   template < class Graph, class OutputIterator, 
williamr@2:              class ColorMap, class DegreeMap>
williamr@2:   OutputIterator 
williamr@2:   cuthill_mckee_ordering(const Graph& G, OutputIterator permutation, 
williamr@2:                          ColorMap color, DegreeMap degree)
williamr@2:   {
williamr@2:     if (vertices(G).first == vertices(G).second)
williamr@2:       return permutation;
williamr@2: 
williamr@2:     typedef typename boost::graph_traits<Graph>::vertex_descriptor Vertex;
williamr@2:     typedef typename boost::graph_traits<Graph>::vertex_iterator   VerIter;
williamr@2:     typedef typename property_traits<ColorMap>::value_type ColorValue;
williamr@2:     typedef color_traits<ColorValue> Color;
williamr@2: 
williamr@2:     std::deque<Vertex>      vertex_queue;
williamr@2: 
williamr@2:     // Mark everything white
williamr@2:     BGL_FORALL_VERTICES_T(v, G, Graph) put(color, v, Color::white());
williamr@2: 
williamr@2:     // Find one vertex from each connected component 
williamr@2:     BGL_FORALL_VERTICES_T(v, G, Graph) {
williamr@2:       if (get(color, v) == Color::white()) {
williamr@2:         depth_first_visit(G, v, dfs_visitor<>(), color);
williamr@2:         vertex_queue.push_back(v);
williamr@2:       }
williamr@2:     }
williamr@2: 
williamr@2:     // Find starting nodes for all vertices
williamr@2:     // TBD: How to do this with a directed graph?
williamr@2:     for (typename std::deque<Vertex>::iterator i = vertex_queue.begin();
williamr@2:          i != vertex_queue.end(); ++i)
williamr@2:       *i = find_starting_node(G, *i, color, degree);
williamr@2:     
williamr@2:     return cuthill_mckee_ordering(G, vertex_queue, permutation,
williamr@2:                                   color, degree);
williamr@2:   }
williamr@2: 
williamr@2:   template<typename Graph, typename OutputIterator, typename VertexIndexMap>
williamr@2:   OutputIterator 
williamr@2:   cuthill_mckee_ordering(const Graph& G, OutputIterator permutation, 
williamr@2:                          VertexIndexMap index_map)
williamr@2:   {
williamr@2:     if (vertices(G).first == vertices(G).second)
williamr@2:       return permutation;
williamr@2:     
williamr@2:     typedef out_degree_property_map<Graph> DegreeMap;
williamr@2:     std::vector<default_color_type> colors(num_vertices(G));
williamr@2:     return cuthill_mckee_ordering(G, permutation, 
williamr@2:                                   make_iterator_property_map(&colors[0], 
williamr@2:                                                              index_map,
williamr@2:                                                              colors[0]),
williamr@2:                                   make_out_degree_map(G));
williamr@2:   }
williamr@2: 
williamr@2:   template<typename Graph, typename OutputIterator>
williamr@2:   inline OutputIterator 
williamr@2:   cuthill_mckee_ordering(const Graph& G, OutputIterator permutation)
williamr@2:   { return cuthill_mckee_ordering(G, permutation, get(vertex_index, G)); }
williamr@2: } // namespace boost
williamr@2: 
williamr@2: 
williamr@2: #endif // BOOST_GRAPH_CUTHILL_MCKEE_HPP