1 | /* |
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2 | * A* Shortest path algorithm for PostgreSQL |
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3 | * |
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4 | * Copyright (c) 2006 Anton A. Patrushev, Orkney, Inc. |
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5 | * |
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6 | * This program is free software; you can redistribute it and/or modify |
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7 | * it under the terms of the GNU General Public License as published by |
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8 | * the Free Software Foundation; either version 2 of the License, or |
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9 | * (at your option) any later version. |
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10 | * |
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11 | * This program is distributed in the hope that it will be useful, |
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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14 | * GNU General Public License for more details. |
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15 | * |
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16 | * You should have received a copy of the GNU General Public License |
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17 | * along with this program; if not, write to the Free Software |
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18 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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19 | * |
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20 | */ |
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21 | |
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22 | #include <boost/config.hpp> |
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23 | |
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24 | #include <boost/graph/graph_traits.hpp> |
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25 | #include <boost/graph/adjacency_list.hpp> |
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26 | #include <boost/graph/astar_search.hpp> |
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27 | |
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28 | #include "astar.h" |
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29 | |
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30 | #include <cmath> // for sqrt |
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31 | |
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32 | using namespace std; |
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33 | using namespace boost; |
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34 | |
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35 | // Maximal number of nodes in the path (to avoid infinite loops) |
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36 | #define MAX_NODES 100000000 |
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37 | |
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38 | struct Edge |
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39 | { |
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40 | int id; |
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41 | float8 cost; |
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42 | //float8 distance; |
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43 | }; |
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44 | |
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45 | struct Vertex |
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46 | { |
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47 | int id; |
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48 | float8 x; |
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49 | float8 y; |
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50 | }; |
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51 | |
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52 | |
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53 | struct found_goal {}; // exception for termination |
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54 | |
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55 | // visitor that terminates when we find the goal |
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56 | template <class Vertex> |
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57 | class astar_goal_visitor : public boost::default_astar_visitor |
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58 | { |
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59 | public: |
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60 | astar_goal_visitor(Vertex goal) : m_goal(goal) {} |
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61 | template <class Graph> |
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62 | void examine_vertex(Vertex u, Graph& g) { |
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63 | if(u == m_goal) |
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64 | throw found_goal(); |
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65 | } |
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66 | private: |
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67 | Vertex m_goal; |
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68 | }; |
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69 | |
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70 | // Heuristic function which tells us how far the current node is |
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71 | // from the target node. |
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72 | // |
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73 | // (|dx|+|dy|)/2 is used currently. |
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74 | template <class Graph, class CostType> |
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75 | class distance_heuristic : public astar_heuristic<Graph, CostType> |
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76 | { |
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77 | public: |
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78 | typedef typename graph_traits<Graph>::vertex_descriptor Vertex; |
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79 | distance_heuristic(Graph& g, Vertex goal):m_g(g), m_goal(goal){} |
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80 | CostType operator()(Vertex u) |
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81 | { |
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82 | CostType dx = m_g[m_goal].x - m_g[u].x; |
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83 | CostType dy = m_g[m_goal].y - m_g[u].y; |
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84 | //You can choose any heuristical function from below |
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85 | //return ::max(dx, dy); |
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86 | //return ::sqrt(dx * dx + dy * dy)/4; |
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87 | //return 0; |
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88 | return (::fabs(dx)+::fabs(dy))/2; |
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89 | } |
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90 | private: |
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91 | Graph& m_g; |
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92 | Vertex m_goal; |
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93 | }; |
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94 | |
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95 | |
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96 | // Adds an edge to the graph. |
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97 | // Edge id, cost, source and target ids and coordinates are copied also |
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98 | template <class G, class E> |
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99 | static void |
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100 | graph_add_edge(G &graph, int id, int source, int target, |
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101 | float8 cost, float8 s_x, float8 s_y, float8 t_x, float8 t_y) |
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102 | { |
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103 | E e; |
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104 | bool inserted; |
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105 | |
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106 | if (cost < 0) // edges are not inserted in the graph if cost is negative |
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107 | return; |
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108 | |
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109 | tie(e, inserted) = add_edge(source, target, graph); |
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110 | |
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111 | graph[e].cost = cost; |
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112 | graph[e].id = id; |
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113 | |
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114 | typedef typename graph_traits<G>::vertex_descriptor Vertex; |
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115 | Vertex s = vertex(source, graph); |
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116 | Vertex t = vertex(target, graph); |
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117 | graph[s].x=s_x; |
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118 | graph[s].y=s_y; |
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119 | graph[t].x=t_x; |
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120 | graph[t].y=t_y; |
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121 | } |
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122 | |
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123 | int |
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124 | boost_astar(edge_astar_t *edges, unsigned int count, |
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125 | int source_vertex_id, int target_vertex_id, |
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126 | bool directed, bool has_reverse_cost, |
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127 | path_element_t **path, int *path_count, char **err_msg) |
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128 | { |
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129 | |
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130 | // FIXME: use a template for the directedS parameters |
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131 | typedef adjacency_list < listS, vecS, directedS, Vertex, Edge> graph_t; |
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132 | |
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133 | typedef graph_traits < graph_t >::vertex_descriptor vertex_descriptor; |
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134 | typedef graph_traits < graph_t >::edge_descriptor edge_descriptor; |
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135 | |
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136 | // FIXME: compute this value |
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137 | const unsigned int num_nodes = ((directed && has_reverse_cost ? 2 : 1) * |
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138 | count) + 100; |
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139 | |
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140 | graph_t graph(num_nodes); |
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141 | |
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142 | property_map<graph_t, edge_weight_t>::type weightmap = get(edge_weight, |
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143 | graph); |
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144 | |
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145 | for (std::size_t j = 0; j < count; ++j) |
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146 | { |
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147 | |
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148 | graph_add_edge<graph_t, edge_descriptor>(graph, |
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149 | edges[j].id, edges[j].source, |
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150 | edges[j].target, edges[j].cost, |
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151 | edges[j].s_x, edges[j].s_y, |
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152 | edges[j].t_x, edges[j].t_y); |
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153 | |
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154 | if (!directed || (directed && has_reverse_cost)) |
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155 | { |
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156 | float8 cost; |
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157 | |
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158 | if (has_reverse_cost) |
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159 | { |
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160 | cost = edges[j].reverse_cost; |
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161 | } |
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162 | else |
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163 | { |
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164 | cost = edges[j].cost; |
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165 | } |
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166 | |
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167 | graph_add_edge<graph_t, edge_descriptor>(graph, |
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168 | edges[j].id, |
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169 | edges[j].target, |
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170 | edges[j].source, |
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171 | cost, |
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172 | edges[j].s_x, |
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173 | edges[j].s_y, |
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174 | edges[j].t_x, |
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175 | edges[j].t_y); |
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176 | } |
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177 | } |
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178 | |
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179 | std::vector<vertex_descriptor> predecessors(num_vertices(graph)); |
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180 | |
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181 | vertex_descriptor source_vertex = vertex(source_vertex_id, graph); |
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182 | |
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183 | if (source_vertex < 0) |
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184 | { |
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185 | *err_msg = (char *) "Source vertex not found"; |
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186 | return -1; |
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187 | } |
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188 | |
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189 | vertex_descriptor target_vertex = vertex(target_vertex_id, graph); |
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190 | if (target_vertex < 0) |
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191 | { |
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192 | *err_msg = (char *) "Target vertex not found"; |
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193 | return -1; |
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194 | } |
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195 | |
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196 | std::vector<float8> distances(num_vertices(graph)); |
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197 | |
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198 | try { |
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199 | // Call A* named parameter interface |
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200 | astar_search |
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201 | (graph, source_vertex, |
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202 | distance_heuristic<graph_t, float>(graph, target_vertex), |
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203 | predecessor_map(&predecessors[0]). |
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204 | weight_map(get(&Edge::cost, graph)). |
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205 | distance_map(&distances[0]). |
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206 | visitor(astar_goal_visitor<vertex_descriptor>(target_vertex))); |
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207 | |
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208 | } |
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209 | catch(found_goal fg) { |
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210 | // Target vertex found |
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211 | vector<int> path_vect; |
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212 | int max = MAX_NODES; |
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213 | path_vect.push_back(target_vertex); |
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214 | |
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215 | while (target_vertex != source_vertex) |
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216 | { |
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217 | if (target_vertex == predecessors[target_vertex]) |
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218 | { |
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219 | *err_msg = (char *) "No path found"; |
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220 | return 0; |
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221 | |
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222 | } |
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223 | target_vertex = predecessors[target_vertex]; |
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224 | |
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225 | path_vect.push_back(target_vertex); |
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226 | if (!max--) |
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227 | { |
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228 | *err_msg = (char *) "Overflow"; |
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229 | return -1; |
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230 | } |
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231 | } |
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232 | |
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233 | *path = (path_element_t *) malloc(sizeof(path_element_t) * |
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234 | (path_vect.size() + 1)); |
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235 | *path_count = path_vect.size(); |
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236 | |
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237 | for(int i = path_vect.size() - 1, j = 0; i >= 0; i--, j++) |
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238 | { |
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239 | graph_traits < graph_t >::vertex_descriptor v_src; |
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240 | graph_traits < graph_t >::vertex_descriptor v_targ; |
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241 | graph_traits < graph_t >::edge_descriptor e; |
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242 | graph_traits < graph_t >::out_edge_iterator out_i, out_end; |
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243 | |
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244 | (*path)[j].vertex_id = path_vect.at(i); |
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245 | |
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246 | (*path)[j].edge_id = -1; |
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247 | (*path)[j].cost = distances[target_vertex]; |
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248 | |
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249 | if (i == 0) |
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250 | { |
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251 | continue; |
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252 | } |
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253 | |
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254 | v_src = path_vect.at(i); |
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255 | v_targ = path_vect.at(i - 1); |
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256 | |
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257 | for (tie(out_i, out_end) = out_edges(v_src, graph); |
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258 | out_i != out_end; ++out_i) |
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259 | { |
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260 | graph_traits < graph_t >::vertex_descriptor v, targ; |
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261 | e = *out_i; |
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262 | v = source(e, graph); |
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263 | targ = target(e, graph); |
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264 | |
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265 | if (targ == v_targ) |
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266 | { |
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267 | (*path)[j].edge_id = graph[*out_i].id; |
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268 | (*path)[j].cost = graph[*out_i].cost; |
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269 | break; |
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270 | } |
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271 | } |
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272 | } |
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273 | |
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274 | return EXIT_SUCCESS; |
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275 | } |
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276 | } |
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277 | |
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