1 | // Parallel abstract graph traverser. Contributed by Bjarne Knudsen. |
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2 | |
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3 | #include <iostream> |
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4 | #include <vector> |
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5 | #include <deque> |
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6 | #include <thread> |
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7 | #include <condition_variable> |
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8 | //#include <chrono> |
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9 | #include <iomanip> |
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10 | |
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11 | #include "gfanlib_paralleltraverser.h" |
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12 | |
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13 | /* |
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14 | TODO: |
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15 | |
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16 | - Consider giving JobTransfers an affinity to a specific thread. |
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17 | |
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18 | - Consider if the amount of entries to be copied in the stack for |
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19 | deep searches can be reduced. |
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20 | |
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21 | - Consider making a more compact stack for limited in and out edge |
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22 | counts. |
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23 | */ |
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24 | |
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25 | using namespace std; |
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26 | |
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27 | namespace gfan{ |
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28 | |
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29 | // This struct holds information about one step of a traversal. |
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30 | struct TraverseState { |
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31 | // The number of next edges |
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32 | int next_count; |
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33 | |
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34 | // The index of the next edge that was followed |
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35 | int next_index; |
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36 | |
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37 | // The index of the previous edge to get back |
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38 | int prev_index; |
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39 | |
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40 | TraverseState( int next_count, |
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41 | int next_index, |
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42 | int prev_index ) |
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43 | { |
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44 | this->next_count = next_count; |
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45 | this->next_index = next_index; |
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46 | this->prev_index = prev_index; |
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47 | } |
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48 | }; |
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49 | |
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50 | |
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51 | void traverse_simple_recursive( Traverser* traverser ) |
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52 | { |
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53 | int count = traverser->getEdgeCountNext(); |
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54 | |
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55 | traverser->collectInfo(); |
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56 | |
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57 | for (int i = 0; i < count; i++) { |
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58 | int prev_index = traverser->moveToNext(i, true); |
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59 | |
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60 | if (prev_index == 0) { |
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61 | // Only traverse each state once, so do it for the zero'th |
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62 | // parent. |
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63 | traverse_simple_recursive(traverser); |
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64 | } |
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65 | |
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66 | traverser->moveToPrev(prev_index); |
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67 | } |
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68 | } |
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69 | |
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70 | |
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71 | // This function creates a stack that represents the full job to be |
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72 | // done. Info is also collected for the start state. |
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73 | vector<TraverseState>* create_first_job_stack( Traverser* traverser ) |
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74 | { |
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75 | vector<TraverseState>* stack = new vector<TraverseState>(); |
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76 | |
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77 | stack->push_back(TraverseState(traverser->getEdgeCountNext(), -1, -1)); |
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78 | |
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79 | traverser->collectInfo(); |
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80 | |
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81 | return stack; |
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82 | } |
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83 | |
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84 | |
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85 | void traverse_simple_stack( Traverser* traverser ) |
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86 | { |
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87 | // The stack holds information about what we have done so far |
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88 | vector<TraverseState>* stack = create_first_job_stack(traverser); |
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89 | |
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90 | while (!stack->empty()) { |
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91 | stack->back().next_index++; |
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92 | |
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93 | TraverseState state = stack->back(); |
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94 | |
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95 | if (state.next_index == state.next_count || traverser->aborting /* Added by Anders */) { |
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96 | if (state.prev_index != -1) { |
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97 | traverser->moveToPrev(state.prev_index); |
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98 | } |
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99 | stack->pop_back(); |
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100 | } |
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101 | else { |
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102 | int prev_index = traverser->moveToNext(state.next_index, true); |
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103 | |
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104 | if (prev_index == 0) { |
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105 | traverser->collectInfo(); |
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106 | stack->push_back(TraverseState(traverser->getEdgeCountNext(), -1, prev_index)); |
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107 | } |
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108 | else { |
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109 | traverser->moveToPrev(prev_index); |
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110 | } |
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111 | } |
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112 | } |
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113 | |
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114 | delete stack; |
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115 | } |
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116 | |
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117 | |
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118 | void traverse_simple( Traverser* traverser ) |
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119 | { |
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120 | traverse_simple_stack(traverser); |
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121 | } |
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122 | |
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123 | |
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124 | // A Job holds a traverser and a stack representing the job. The stack |
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125 | // is changed along with the traverser, so it represents the state of |
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126 | // the traverser. |
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127 | class Job { |
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128 | Traverser* traverser; |
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129 | |
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130 | vector<TraverseState>* stack; |
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131 | |
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132 | // The lowest index in the stack where there is some unfinished |
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133 | // work. -1 if there is no unfinished work. |
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134 | int first_split; |
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135 | |
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136 | // For a given starting point, find the first index of the stack |
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137 | // with unfinished work. -1 if there is no unfinished work. |
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138 | static int find_first_split( vector<TraverseState>* stack, |
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139 | int start ) |
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140 | { |
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141 | auto it = stack->begin(); |
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142 | |
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143 | it += start; |
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144 | while (it != stack->end() && it->next_index == it->next_count - 1) { |
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145 | start++; |
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146 | it++; |
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147 | } |
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148 | |
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149 | if (it == stack->end()) { |
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150 | return -1; |
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151 | } |
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152 | else if (it->next_index == -1 && it->next_count == 1) { |
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153 | return -1; |
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154 | } |
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155 | |
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156 | return start; |
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157 | } |
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158 | |
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159 | |
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160 | public: |
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161 | bool aborting; // Added by Anders |
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162 | // Create a new Job. if first_split is not set (or it is -2), the |
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163 | // first split will be found. |
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164 | Job( vector<TraverseState>* stack = new vector<TraverseState>(), |
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165 | int first_split = -2 ) |
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166 | :aborting(false) // Added by Anders |
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167 | { |
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168 | if (first_split == -2) { |
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169 | first_split = find_first_split(stack, 0); |
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170 | } |
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171 | |
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172 | this->stack = stack; |
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173 | this->first_split = first_split; |
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174 | } |
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175 | |
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176 | |
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177 | ~Job( void ) |
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178 | { |
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179 | delete stack; |
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180 | } |
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181 | |
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182 | |
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183 | // Set the traverser and move it to the start of this job based on |
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184 | // its last job. |
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185 | void setTraverser( Traverser* traverser, |
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186 | Job* last_job ) |
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187 | { |
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188 | vector<TraverseState>* last_stack = last_job->stack; |
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189 | unsigned int i; |
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190 | |
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191 | this->traverser = traverser; |
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192 | |
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193 | // Find the first state where the stacks differ: |
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194 | for (i = 0; i < last_stack->size() && i < stack->size(); i++) { |
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195 | if ((*stack)[i].next_index != (*last_stack)[i].next_index) { |
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196 | break; |
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197 | } |
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198 | } |
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199 | |
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200 | if (i > 0) { |
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201 | // TODO: why is this needed? |
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202 | i--; |
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203 | } |
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204 | |
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205 | // roll back to the division point |
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206 | while (last_stack->size() > i + 1) { |
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207 | traverser->moveToPrev(last_stack->back().prev_index); |
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208 | last_stack->pop_back(); |
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209 | } |
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210 | if (!last_stack->empty()) { |
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211 | last_stack->pop_back(); |
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212 | } |
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213 | |
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214 | // go forward so the traverser represents the new job |
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215 | for (; i < stack->size() - 1; i++) { |
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216 | traverser->moveToNext((*stack)[i].next_index, false); |
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217 | } |
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218 | } |
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219 | |
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220 | |
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221 | // This function does some work and returns false when there is no |
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222 | // more work. Otherwise does at least step_count steps and returns |
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223 | // true when there is a subjob available. |
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224 | bool step( int step_count ) |
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225 | { |
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226 | int steps = 0; |
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227 | |
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228 | // keep going if there is no subjob available |
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229 | while (steps < step_count || first_split == -1) { |
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230 | if (stack->empty()) { |
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231 | return false; |
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232 | } |
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233 | |
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234 | stack->back().next_index++; |
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235 | |
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236 | TraverseState state = stack->back(); |
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237 | |
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238 | if (state.next_index == state.next_count || aborting /* Added by Anders */) { |
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239 | if (state.prev_index != -1) { |
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240 | traverser->moveToPrev(state.prev_index); |
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241 | } |
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242 | stack->pop_back(); |
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243 | |
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244 | if (first_split == -1) { |
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245 | // There is no more work to do in the previous states |
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246 | return false; |
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247 | } |
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248 | } |
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249 | else { |
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250 | if ((int) stack->size() - 1 == first_split) { |
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251 | if (state.next_index == state.next_count - 1) { |
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252 | first_split = -1; |
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253 | } |
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254 | } |
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255 | |
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256 | int prev_index = traverser->moveToNext(state.next_index, true); |
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257 | aborting=traverser->aborting; /* Added by Anders */ |
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258 | steps++; |
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259 | |
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260 | if (prev_index == 0) { |
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261 | int count = traverser->getEdgeCountNext(); |
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262 | |
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263 | traverser->collectInfo(); |
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264 | |
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265 | if (first_split == -1 && count > 1) { |
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266 | first_split = stack->size(); |
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267 | } |
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268 | |
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269 | stack->push_back(TraverseState(count, -1, prev_index)); |
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270 | } |
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271 | else { |
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272 | traverser->moveToPrev(prev_index); |
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273 | } |
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274 | } |
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275 | } |
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276 | |
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277 | return true; |
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278 | } |
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279 | |
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280 | |
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281 | // Get a new subjob of the current job and adjust the current job so |
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282 | // it does not overlap with the new subjob. first_split may not be |
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283 | // -1 when calling this function. |
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284 | Job* getSubjob( void ) |
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285 | { |
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286 | // We can assume that first_split >= 0. |
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287 | auto it = stack->begin(); |
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288 | |
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289 | it += first_split + 1; |
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290 | // this new job will do the rest |
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291 | vector<TraverseState>* new_stack = new vector<TraverseState>(stack->begin(), it); |
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292 | it--; |
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293 | |
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294 | // limit the existing job |
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295 | it->next_count = it->next_index + 1; |
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296 | |
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297 | Job* new_job = new Job(new_stack, find_first_split(new_stack, first_split)); |
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298 | |
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299 | first_split = find_first_split(stack, first_split); |
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300 | |
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301 | return new_job; |
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302 | } |
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303 | |
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304 | |
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305 | void print( void ) |
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306 | { |
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307 | cout << "--cc-nn-pp----------" << endl; |
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308 | for(vector<TraverseState>::const_iterator state=stack->begin();state!=stack->end();state++){ |
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309 | // for (TraverseState state : *stack) { |
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310 | cout << " " << setw(2) << state->next_count << " " << setw(2) << state->next_index |
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311 | << " " << setw(2) << state->prev_index << endl; |
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312 | } |
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313 | cout << "--------------------" << endl; |
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314 | } |
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315 | }; |
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316 | |
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317 | |
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318 | // This class is used to safely transfer a job from one thread to another |
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319 | class JobTransfer { |
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320 | bool is_set; |
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321 | |
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322 | Job* job; |
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323 | |
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324 | mutex mtx; |
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325 | |
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326 | condition_variable cond; |
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327 | |
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328 | public: |
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329 | JobTransfer( void ) |
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330 | { |
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331 | is_set = false; |
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332 | } |
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333 | |
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334 | |
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335 | void setJob( Job* job ) |
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336 | { |
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337 | mtx.lock(); |
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338 | |
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339 | this->job = job; |
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340 | is_set = true; |
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341 | |
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342 | // notify should be done after unlock according to |
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343 | // http://en.cppreference.com/w/cpp/thread/condition_variable/notify_one |
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344 | // but doing so seems to cause a deadlock with 8 threads using |
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345 | // SubsetTraversers of size 16 on my laptop |
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346 | cond.notify_one(); |
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347 | mtx.unlock(); |
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348 | } |
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349 | |
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350 | |
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351 | Job* getJob( void ) |
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352 | { |
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353 | unique_lock<mutex> lock(mtx); |
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354 | |
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355 | while (!is_set) { |
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356 | cond.wait(lock); |
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357 | } |
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358 | |
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359 | lock.unlock(); |
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360 | |
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361 | return job; |
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362 | } |
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363 | }; |
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364 | |
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365 | |
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366 | class JobCentral; |
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367 | |
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368 | // A struct for holding all the information needed by a thread. |
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369 | struct ThreadContext { |
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370 | JobCentral* central; |
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371 | |
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372 | Traverser* traverser; |
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373 | |
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374 | int step_count; |
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375 | |
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376 | ThreadContext( JobCentral* central, |
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377 | Traverser* traverser, |
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378 | int step_count ) |
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379 | { |
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380 | this->central = central; |
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381 | this->traverser = traverser; |
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382 | this->step_count = step_count; |
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383 | } |
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384 | }; |
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385 | |
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386 | |
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387 | void work( ThreadContext* context ); |
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388 | |
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389 | |
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390 | // This class is used running the whole threaded traversal and for |
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391 | // exchanging jobs between threads |
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392 | class JobCentral { |
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393 | ThreadContext** contexts; |
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394 | |
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395 | int context_count; |
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396 | |
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397 | int step_count; |
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398 | |
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399 | Job* first_job; |
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400 | |
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401 | mutex mtx; |
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402 | |
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403 | // This queue is used for transferring jobs between threads. When a |
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404 | // thread requests a job, an empty transfer is put in this queue. It |
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405 | // will then be picked up by a thread that has a subjob |
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406 | // available. The subjob is given to the JobTransfer and is then |
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407 | // received by the thread needing it. |
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408 | deque<JobTransfer*>* transfers; |
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409 | |
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410 | public: |
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411 | bool aborting; // Added by Anders |
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412 | // step_count is the number of algorithm steps taken between |
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413 | // possible job transfers. This value should be high (e.g. 100) if |
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414 | // the traverser is very fast. If the traverser is slow, step_count |
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415 | // should be one. |
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416 | JobCentral( Traverser** traversers, |
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417 | int count, |
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418 | int step_count ) |
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419 | :aborting(false) // Added by Anders |
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420 | { |
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421 | context_count = count; |
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422 | contexts = new ThreadContext*[count]; |
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423 | |
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424 | for (int i = 0; i < count; i++) { |
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425 | contexts[i] = new ThreadContext(this, traversers[i], step_count); |
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426 | } |
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427 | |
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428 | transfers = new deque<JobTransfer*>(); |
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429 | } |
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430 | |
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431 | |
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432 | ~JobCentral( void ) |
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433 | { |
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434 | delete transfers; |
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435 | for (int i = 0; i < context_count; i++) { |
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436 | delete contexts[i]; |
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437 | } |
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438 | delete[] contexts; |
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439 | } |
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440 | |
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441 | |
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442 | // Run a job in multiple threads. This function is usually just |
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443 | // called once with a job representing everything to be done. |
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444 | void runJob( Job* job ) |
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445 | { |
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446 | thread** thr = new thread*[context_count]; |
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447 | |
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448 | this->first_job = job; |
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449 | |
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450 | for (int i = 0; i < context_count; i++) { |
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451 | thr[i] = new thread(work, contexts[i]); |
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452 | } |
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453 | |
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454 | for (int i = 0; i < context_count; i++) { |
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455 | thr[i]->join(); |
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456 | delete thr[i]; |
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457 | } |
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458 | |
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459 | delete[] thr; |
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460 | } |
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461 | |
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462 | |
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463 | bool hasTransfer( void ) |
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464 | { |
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465 | return !transfers->empty(); |
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466 | } |
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467 | |
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468 | |
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469 | // If no threads are requesting jobs, the return value will be |
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470 | // NULL. Otherwise a JobTransfer will be returned ready for |
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471 | // receiving a new job. |
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472 | JobTransfer* getTransfer( void ) |
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473 | { |
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474 | JobTransfer* transfer = NULL; |
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475 | |
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476 | mtx.lock(); |
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477 | |
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478 | if (!transfers->empty()) { |
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479 | transfer = transfers->back(); |
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480 | transfers->pop_back(); |
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481 | } |
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482 | |
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483 | mtx.unlock(); |
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484 | |
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485 | return transfer; |
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486 | } |
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487 | |
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488 | |
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489 | // Requst a job from another thread. The return value is NULL if all |
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490 | // jobs are done. |
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491 | Job* getJob( void ) |
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492 | { |
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493 | Job* job = NULL; |
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494 | |
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495 | mtx.lock(); |
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496 | |
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497 | if (first_job != NULL) { |
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498 | job = first_job; |
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499 | first_job = NULL; |
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500 | } |
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501 | else if ((int) transfers->size() < context_count - 1) { |
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502 | JobTransfer* transfer = new JobTransfer(); |
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503 | |
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504 | transfers->push_front(transfer); |
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505 | |
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506 | mtx.unlock(); |
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507 | |
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508 | job = transfer->getJob(); |
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509 | |
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510 | delete transfer; |
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511 | |
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512 | // return now because the mutex is already unlocked |
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513 | return job; |
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514 | } |
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515 | else { |
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516 | // We are fully done |
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517 | |
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518 | for(deque<JobTransfer*>::const_iterator tr=transfers->begin();tr!=transfers->end();tr++){ |
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519 | // for (JobTransfer* tr : *transfers) { |
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520 | (*tr)->setJob(NULL); |
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521 | } |
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522 | } |
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523 | |
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524 | mtx.unlock(); |
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525 | |
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526 | return job; |
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527 | } |
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528 | }; |
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529 | |
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530 | |
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531 | // Do the actual work |
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532 | void work( ThreadContext* context ) |
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533 | { |
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534 | Traverser* traverser = context->traverser; |
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535 | JobCentral* central = context->central; |
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536 | Job* job; |
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537 | Job* last_job = new Job(); |
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538 | |
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539 | while ((job = central->getJob()) != NULL) { |
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540 | job->setTraverser(traverser, last_job); |
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541 | |
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542 | int step_count = central->hasTransfer() ? 1 : context->step_count; |
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543 | |
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544 | if(central->aborting)job->aborting=true; // Added by Anders |
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545 | |
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546 | while (job->step(step_count)) { |
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547 | if(job->aborting)central->aborting=true; // Added by Anders |
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548 | JobTransfer* transfer = central->getTransfer(); |
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549 | |
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550 | if (transfer != NULL) { |
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551 | transfer->setJob(job->getSubjob()); |
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552 | } |
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553 | |
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554 | step_count = central->hasTransfer() ? 1 : context->step_count; |
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555 | } |
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556 | |
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557 | delete last_job; |
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558 | last_job = job; |
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559 | } |
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560 | |
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561 | delete last_job; |
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562 | } |
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563 | |
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564 | |
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565 | // Do the actual work |
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566 | void work2( ThreadContext* context ) |
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567 | { |
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568 | Traverser* traverser = context->traverser; |
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569 | JobCentral* central = context->central; |
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570 | int step_count = context->step_count; |
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571 | Job* job; |
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572 | Job* last_job = new Job(); |
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573 | |
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574 | while ((job = central->getJob()) != NULL) { |
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575 | job->setTraverser(traverser, last_job); |
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576 | |
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577 | while (job->step(step_count)) { |
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578 | JobTransfer* transfer = central->getTransfer(); |
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579 | |
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580 | if (transfer != NULL) { |
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581 | transfer->setJob(job->getSubjob()); |
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582 | } |
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583 | } |
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584 | |
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585 | delete last_job; |
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586 | last_job = job; |
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587 | } |
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588 | |
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589 | delete last_job; |
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590 | } |
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591 | |
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592 | |
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593 | void traverse_threaded( Traverser** traversers, |
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594 | int count, |
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595 | int step_count ) |
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596 | { |
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597 | JobCentral* central = new JobCentral(traversers, count, step_count); |
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598 | |
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599 | central->runJob(new Job(create_first_job_stack(traversers[0]))); |
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600 | |
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601 | delete central; |
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602 | } |
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603 | } |
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