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