boost/graph/dag_shortest_paths.hpp

   1 //=======================================================================
   2 // Copyright 2002 Indiana University.
   3 // Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
   4 //
   5 // Distributed under the Boost Software License, Version 1.0. (See
   6 // accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt)
   8 //=======================================================================
   9
  10 #ifndef BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
  11 #define BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
  12
  13 #include <boost/graph/topological_sort.hpp>
  14 #include <boost/graph/dijkstra_shortest_paths.hpp>
  15
  16 // single-source shortest paths for a Directed Acyclic Graph (DAG)
  17
  18 namespace boost {
  19
  20   // Initalize distances and call depth first search
  21   template <class VertexListGraph, class DijkstraVisitor,
  22             class DistanceMap, class WeightMap, class ColorMap,
  23             class PredecessorMap,
  24             class Compare, class Combine,
  25             class DistInf, class DistZero>
  26   inline void
  27   dag_shortest_paths
  28     (const VertexListGraph& g,
  29      typename graph_traits<VertexListGraph>::vertex_descriptor s,
  30      DistanceMap distance, WeightMap weight, ColorMap color,
  31      PredecessorMap pred,
  32      DijkstraVisitor vis, Compare compare, Combine combine,
  33      DistInf inf, DistZero zero)
  34   {
  35     typedef typename graph_traits<VertexListGraph>::vertex_descriptor Vertex;
  36     std::vector<Vertex> rev_topo_order;
  37     rev_topo_order.reserve(num_vertices(g));
  38
  39     // Call 'depth_first_visit', not 'topological_sort', because we don't
  40     // want to traverse the entire graph, only vertices reachable from 's',
  41     // and 'topological_sort' will traverse everything. The logic below
  42     // is the same as for 'topological_sort', only we call 'depth_first_visit'
  43     // and 'topological_sort' calls 'depth_first_search'.
  44     topo_sort_visitor<std::back_insert_iterator<std::vector<Vertex> > >
  45         topo_visitor(std::back_inserter(rev_topo_order));
  46     depth_first_visit(g, s, topo_visitor, color);
  47
  48     typename graph_traits<VertexListGraph>::vertex_iterator ui, ui_end;
  49     for (tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui) {
  50       put(distance, *ui, inf);
  51       put(pred, *ui, *ui);
  52     }
  53
  54     put(distance, s, zero);
  55     vis.discover_vertex(s, g);
  56     typename std::vector<Vertex>::reverse_iterator i;
  57     for (i = rev_topo_order.rbegin(); i != rev_topo_order.rend(); ++i) {
  58       Vertex u = *i;
  59       vis.examine_vertex(u, g);
  60       typename graph_traits<VertexListGraph>::out_edge_iterator e, e_end;
  61       for (tie(e, e_end) = out_edges(u, g); e != e_end; ++e) {
  62         vis.discover_vertex(target(*e, g), g);
  63         bool decreased = relax(*e, g, weight, pred, distance,
  64                                combine, compare);
  65         if (decreased)
  66           vis.edge_relaxed(*e, g);
  67         else
  68           vis.edge_not_relaxed(*e, g);
  69       }
  70       vis.finish_vertex(u, g);
  71     }
  72   }
  73
  74   namespace detail {
  75
  76     // Defaults are the same as Dijkstra's algorithm
  77
  78     // Handle Distance Compare, Combine, Inf and Zero defaults
  79     template <class VertexListGraph, class DijkstraVisitor,
  80       class DistanceMap, class WeightMap, class ColorMap,
  81       class IndexMap, class Params>
  82     inline void
  83     dag_sp_dispatch2
  84       (const VertexListGraph& g,
  85        typename graph_traits<VertexListGraph>::vertex_descriptor s,
  86        DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,
  87        DijkstraVisitor vis, const Params& params)
  88     {
  89       typedef typename property_traits<DistanceMap>::value_type D;
  90       dummy_property_map p_map;
  91       dag_shortest_paths
  92         (g, s, distance, weight, color,
  93          choose_param(get_param(params, vertex_predecessor), p_map),
  94          vis,
  95          choose_param(get_param(params, distance_compare_t()), std::less<D>()),
  96          choose_param(get_param(params, distance_combine_t()), closed_plus<D>()),
  97          choose_param(get_param(params, distance_inf_t()),
  98                       (std::numeric_limits<D>::max)()),
  99          choose_param(get_param(params, distance_zero_t()),
 100                       D()));
 101     }
 102
 103     // Handle DistanceMap and ColorMap defaults
 104     template <class VertexListGraph, class DijkstraVisitor,
 105               class DistanceMap, class WeightMap, class ColorMap,
 106               class IndexMap, class Params>
 107     inline void
 108     dag_sp_dispatch1
 109       (const VertexListGraph& g,
 110        typename graph_traits<VertexListGraph>::vertex_descriptor s,
 111        DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,
 112        DijkstraVisitor vis, const Params& params)
 113     {
 114       typedef typename property_traits<WeightMap>::value_type T;
 115       typename std::vector<T>::size_type n;
 116       n = is_default_param(distance) ? num_vertices(g) : 1;
 117       std::vector<T> distance_map(n);
 118       n = is_default_param(color) ? num_vertices(g) : 1;
 119       std::vector<default_color_type> color_map(n);
 120
 121       dag_sp_dispatch2
 122         (g, s,
 123          choose_param(distance,
 124                       make_iterator_property_map(distance_map.begin(), id,
 125                                                  distance_map[0])),
 126          weight,
 127          choose_param(color,
 128                       make_iterator_property_map(color_map.begin(), id,
 129                                                  color_map[0])),
 130          id, vis, params);
 131     }
 132
 133   } // namespace detail
 134
 135   template <class VertexListGraph, class Param, class Tag, class Rest>
 136   inline void
 137   dag_shortest_paths
 138     (const VertexListGraph& g,
 139      typename graph_traits<VertexListGraph>::vertex_descriptor s,
 140      const bgl_named_params<Param,Tag,Rest>& params)
 141   {
 142     // assert that the graph is directed...
 143     null_visitor null_vis;
 144     detail::dag_sp_dispatch1
 145       (g, s,
 146        get_param(params, vertex_distance),
 147        choose_const_pmap(get_param(params, edge_weight), g, edge_weight),
 148        get_param(params, vertex_color),
 149        choose_const_pmap(get_param(params, vertex_index), g, vertex_index),
 150        choose_param(get_param(params, graph_visitor),
 151                     make_dijkstra_visitor(null_vis)),
 152        params);
 153   }
 154
 155 } // namespace boost
 156
 157 #endif // BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP