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
21 // Initalize distances and call depth first search
22 template < class VertexListGraph, class DijkstraVisitor, class DistanceMap,
23 class WeightMap, class ColorMap, class PredecessorMap, class Compare,
24 class Combine, class DistInf, class DistZero >
dag_shortest_paths(const VertexListGraph & g,typename graph_traits<VertexListGraph>::vertex_descriptor s,DistanceMap distance,WeightMap weight,ColorMap color,PredecessorMap pred,DijkstraVisitor vis,Compare compare,Combine combine,DistInf inf,DistZero zero)25 inline void dag_shortest_paths(const VertexListGraph& g,
26 typename graph_traits< VertexListGraph >::vertex_descriptor s,
27 DistanceMap distance, WeightMap weight, ColorMap color, PredecessorMap pred,
28 DijkstraVisitor vis, Compare compare, Combine combine, DistInf inf,
29 DistZero zero)
30 {
31 typedef typename graph_traits< VertexListGraph >::vertex_descriptor Vertex;
32 std::vector< Vertex > rev_topo_order;
33 rev_topo_order.reserve(num_vertices(g));
34
35 // Call 'depth_first_visit', not 'topological_sort', because we don't
36 // want to traverse the entire graph, only vertices reachable from 's',
37 // and 'topological_sort' will traverse everything. The logic below
38 // is the same as for 'topological_sort', only we call 'depth_first_visit'
39 // and 'topological_sort' calls 'depth_first_search'.
40 topo_sort_visitor< std::back_insert_iterator< std::vector< Vertex > > >
41 topo_visitor(std::back_inserter(rev_topo_order));
42 depth_first_visit(g, s, topo_visitor, color);
43
44 typename graph_traits< VertexListGraph >::vertex_iterator ui, ui_end;
45 for (boost::tie(ui, ui_end) = vertices(g); ui != ui_end; ++ui)
46 {
47 put(distance, *ui, inf);
48 put(pred, *ui, *ui);
49 }
50
51 put(distance, s, zero);
52 vis.discover_vertex(s, g);
53 typename std::vector< Vertex >::reverse_iterator i;
54 for (i = rev_topo_order.rbegin(); i != rev_topo_order.rend(); ++i)
55 {
56 Vertex u = *i;
57 vis.examine_vertex(u, g);
58 typename graph_traits< VertexListGraph >::out_edge_iterator e, e_end;
59 for (boost::tie(e, e_end) = out_edges(u, g); e != e_end; ++e)
60 {
61 vis.discover_vertex(target(*e, g), g);
62 bool decreased
63 = relax(*e, g, weight, pred, distance, combine, compare);
64 if (decreased)
65 vis.edge_relaxed(*e, g);
66 else
67 vis.edge_not_relaxed(*e, g);
68 }
69 vis.finish_vertex(u, g);
70 }
71 }
72
73 namespace detail
74 {
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, class DistanceMap,
80 class WeightMap, class ColorMap, class IndexMap, class Params >
dag_sp_dispatch2(const VertexListGraph & g,typename graph_traits<VertexListGraph>::vertex_descriptor s,DistanceMap distance,WeightMap weight,ColorMap color,IndexMap,DijkstraVisitor vis,const Params & params)81 inline void dag_sp_dispatch2(const VertexListGraph& g,
82 typename graph_traits< VertexListGraph >::vertex_descriptor s,
83 DistanceMap distance, WeightMap weight, ColorMap color, IndexMap /*id*/,
84 DijkstraVisitor vis, const Params& params)
85 {
86 typedef typename property_traits< DistanceMap >::value_type D;
87 dummy_property_map p_map;
88 D inf = choose_param(get_param(params, distance_inf_t()),
89 (std::numeric_limits< D >::max)());
90 dag_shortest_paths(g, s, distance, weight, color,
91 choose_param(get_param(params, vertex_predecessor), p_map), vis,
92 choose_param(
93 get_param(params, distance_compare_t()), std::less< D >()),
94 choose_param(
95 get_param(params, distance_combine_t()), closed_plus< D >(inf)),
96 inf, choose_param(get_param(params, distance_zero_t()), D()));
97 }
98
99 // Handle DistanceMap and ColorMap defaults
100 template < class VertexListGraph, class DijkstraVisitor, class DistanceMap,
101 class WeightMap, class ColorMap, class IndexMap, class Params >
dag_sp_dispatch1(const VertexListGraph & g,typename graph_traits<VertexListGraph>::vertex_descriptor s,DistanceMap distance,WeightMap weight,ColorMap color,IndexMap id,DijkstraVisitor vis,const Params & params)102 inline void dag_sp_dispatch1(const VertexListGraph& g,
103 typename graph_traits< VertexListGraph >::vertex_descriptor s,
104 DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id,
105 DijkstraVisitor vis, const Params& params)
106 {
107 typedef typename property_traits< WeightMap >::value_type T;
108 typename std::vector< T >::size_type n;
109 n = is_default_param(distance) ? num_vertices(g) : 1;
110 std::vector< T > distance_map(n);
111 n = is_default_param(color) ? num_vertices(g) : 1;
112 std::vector< default_color_type > color_map(n);
113
114 dag_sp_dispatch2(g, s,
115 choose_param(distance,
116 make_iterator_property_map(
117 distance_map.begin(), id, distance_map[0])),
118 weight,
119 choose_param(color,
120 make_iterator_property_map(
121 color_map.begin(), id, color_map[0])),
122 id, vis, params);
123 }
124
125 } // namespace detail
126
127 template < class VertexListGraph, class Param, class Tag, class Rest >
dag_shortest_paths(const VertexListGraph & g,typename graph_traits<VertexListGraph>::vertex_descriptor s,const bgl_named_params<Param,Tag,Rest> & params)128 inline void dag_shortest_paths(const VertexListGraph& g,
129 typename graph_traits< VertexListGraph >::vertex_descriptor s,
130 const bgl_named_params< Param, Tag, Rest >& params)
131 {
132 // assert that the graph is directed...
133 null_visitor null_vis;
134 detail::dag_sp_dispatch1(g, s, get_param(params, vertex_distance),
135 choose_const_pmap(get_param(params, edge_weight), g, edge_weight),
136 get_param(params, vertex_color),
137 choose_const_pmap(get_param(params, vertex_index), g, vertex_index),
138 choose_param(
139 get_param(params, graph_visitor), make_dijkstra_visitor(null_vis)),
140 params);
141 }
142
143 } // namespace boost
144
145 #endif // BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP
146