source: NonGTP/Boost/boost/graph/dag_shortest_paths.hpp @ 857

Revision 857, 6.2 KB checked in by igarcia, 19 years ago (diff)
Line 
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
18namespace 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
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