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 (boost::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 (boost::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 | D inf = |
92 | choose_param(get_param(params, distance_inf_t()), |
93 | (std::numeric_limits<D>::max)()); |
94 | dag_shortest_paths |
95 | (g, s, distance, weight, color, |
96 | choose_param(get_param(params, vertex_predecessor), p_map), |
97 | vis, |
98 | choose_param(get_param(params, distance_compare_t()), std::less<D>()), |
99 | choose_param(get_param(params, distance_combine_t()), closed_plus<D>(inf)), |
100 | inf, |
101 | choose_param(get_param(params, distance_zero_t()), |
102 | D())); |
103 | } |
104 | |
105 | // Handle DistanceMap and ColorMap defaults |
106 | template <class VertexListGraph, class DijkstraVisitor, |
107 | class DistanceMap, class WeightMap, class ColorMap, |
108 | class IndexMap, class Params> |
109 | inline void |
110 | dag_sp_dispatch1 |
111 | (const VertexListGraph& g, |
112 | typename graph_traits<VertexListGraph>::vertex_descriptor s, |
113 | DistanceMap distance, WeightMap weight, ColorMap color, IndexMap id, |
114 | DijkstraVisitor vis, const Params& params) |
115 | { |
116 | typedef typename property_traits<WeightMap>::value_type T; |
117 | typename std::vector<T>::size_type n; |
118 | n = is_default_param(distance) ? num_vertices(g) : 1; |
119 | std::vector<T> distance_map(n); |
120 | n = is_default_param(color) ? num_vertices(g) : 1; |
121 | std::vector<default_color_type> color_map(n); |
122 | |
123 | dag_sp_dispatch2 |
124 | (g, s, |
125 | choose_param(distance, |
126 | make_iterator_property_map(distance_map.begin(), id, |
127 | distance_map[0])), |
128 | weight, |
129 | choose_param(color, |
130 | make_iterator_property_map(color_map.begin(), id, |
131 | color_map[0])), |
132 | id, vis, params); |
133 | } |
134 | |
135 | } // namespace detail |
136 | |
137 | template <class VertexListGraph, class Param, class Tag, class Rest> |
138 | inline void |
139 | dag_shortest_paths |
140 | (const VertexListGraph& g, |
141 | typename graph_traits<VertexListGraph>::vertex_descriptor s, |
142 | const bgl_named_params<Param,Tag,Rest>& params) |
143 | { |
144 | // assert that the graph is directed... |
145 | null_visitor null_vis; |
146 | detail::dag_sp_dispatch1 |
147 | (g, s, |
148 | get_param(params, vertex_distance), |
149 | choose_const_pmap(get_param(params, edge_weight), g, edge_weight), |
150 | get_param(params, vertex_color), |
151 | choose_const_pmap(get_param(params, vertex_index), g, vertex_index), |
152 | choose_param(get_param(params, graph_visitor), |
153 | make_dijkstra_visitor(vis: null_vis)), |
154 | params); |
155 | } |
156 | |
157 | } // namespace boost |
158 | |
159 | #endif // BOOST_GRAPH_DAG_SHORTEST_PATHS_HPP |
160 | |