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1 using System;
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2 using System.Collections.Generic;
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3 using System.Linq;
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4 using System.Text;
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5 using System.Threading;
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6 using System.Diagnostics;
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7
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8 namespace Implab.Parallels {
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9 public abstract class DispatchPool<TUnit> : IDisposable {
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10 readonly int m_minThreads;
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11 readonly int m_maxThreads;
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12 int m_runningThreads = 0;
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13 int m_maxRunningThreads = 0;
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14 int m_suspended = 0;
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15 int m_exitRequired = 0;
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16 AutoResetEvent m_hasTasks = new AutoResetEvent(false);
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17
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18 protected DispatchPool(int min, int max) {
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19 if (min < 0)
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20 throw new ArgumentOutOfRangeException("min");
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21 if (max <= 0)
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22 throw new ArgumentOutOfRangeException("max");
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23
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24 if (min > max)
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25 min = max;
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26 m_minThreads = min;
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27 m_maxThreads = max;
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28 }
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29
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30 protected DispatchPool(int threads)
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31 : this(threads, threads) {
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32 }
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33
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34 protected DispatchPool() {
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35 int maxThreads, maxCP;
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36 ThreadPool.GetMaxThreads(out maxThreads, out maxCP);
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37
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38 m_minThreads = 0;
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39 m_maxThreads = maxThreads;
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40 }
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41
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42 protected void InitPool() {
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43 for (int i = 0; i < m_minThreads; i++)
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44 StartWorker();
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45 }
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46
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47 public int ThreadCount {
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48 get {
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49 return m_runningThreads;
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50 }
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51 }
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52
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53 public int MaxRunningThreads {
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54 get {
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55 return m_maxRunningThreads;
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56 }
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57 }
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58
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59 protected bool IsDisposed {
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60 get {
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61 return m_exitRequired != 0;
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62 }
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63 }
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64
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65 bool StartWorker() {
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66 var current = m_runningThreads;
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67 // use spins to allocate slot for the new thread
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68 do {
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69 if (current >= m_maxThreads || m_exitRequired != 0)
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70 // no more slots left or the pool has been disposed
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71 return false;
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72 } while (current != Interlocked.CompareExchange(ref m_runningThreads, current + 1, current));
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73
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74 m_maxRunningThreads = Math.Max(m_maxRunningThreads, current + 1);
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75
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76 // slot successfully allocated
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77
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78 var worker = new Thread(this.Worker);
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79 worker.IsBackground = true;
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80 worker.Start();
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81
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82 return true;
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83 }
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84
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85 protected abstract bool TryDequeue(out TUnit unit);
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86
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87 protected virtual void WakeNewWorker() {
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88 if (m_suspended > 0)
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89 m_hasTasks.Set();
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90 else
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91 StartWorker();
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92 }
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93
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94 bool FetchTask(out TUnit unit) {
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95 do {
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96 // exit if requested
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97 if (m_exitRequired != 0) {
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98 // release the thread slot
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99 int running;
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100 do {
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101 running = m_runningThreads;
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102 } while (running != Interlocked.CompareExchange(ref m_runningThreads, running - 1, running));
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103 running--;
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104
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105 if (running == 0) // it was the last worker
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106 m_hasTasks.Dispose();
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107 else
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108 m_hasTasks.Set(); // release next worker
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109 unit = default(TUnit);
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110 return false;
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111 }
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112
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113 // fetch task
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114 if (TryDequeue(out unit)) {
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115 WakeNewWorker();
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116 return true;
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117 }
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118
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119 //no tasks left, exit if the thread is no longer needed
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120 int runningThreads;
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121 bool exit = true;
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122 do {
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123 runningThreads = m_runningThreads;
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124 if (runningThreads <= m_minThreads) {
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125 exit = false;
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126 break;
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127 }
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128 } while (runningThreads != Interlocked.CompareExchange(ref m_runningThreads, runningThreads - 1, runningThreads));
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129
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130 if (exit) {
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131 Interlocked.Decrement(ref m_runningThreads);
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132 return false;
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133 }
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134
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135 // keep this thread and wait
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136 Interlocked.Increment(ref m_suspended);
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137 m_hasTasks.WaitOne();
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138 Interlocked.Decrement(ref m_suspended);
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139 } while (true);
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140 }
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141
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142 protected abstract void InvokeUnit(TUnit unit);
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143
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144 void Worker() {
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145 TUnit unit;
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146 while (FetchTask(out unit))
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147 InvokeUnit(unit);
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148 }
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149
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150 protected virtual void Dispose(bool disposing) {
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151 if (disposing) {
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152 if (m_exitRequired == 0) {
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153 if (Interlocked.CompareExchange(ref m_exitRequired, 1, 0) != 0)
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154 return;
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155
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156 // wake sleeping threads
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157 m_hasTasks.Set();
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158 GC.SuppressFinalize(this);
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159 }
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160 }
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161 }
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162
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163 public void Dispose() {
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164 Dispose(true);
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165 }
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166
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167 ~DispatchPool() {
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168 Dispose(false);
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169 }
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170 }
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171 }
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