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1 // Written in the D programming language
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2 // www.digitalmars.com/d/
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3
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4 /*
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5 * The contents of this file are subject to the Mozilla Public License Version
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6 * 1.1 (the "License"); you may not use this file except in compliance with
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7 * the License. You may obtain a copy of the License at
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8 * http://www.mozilla.org/MPL/
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9 *
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10 * Software distributed under the License is distributed on an "AS IS" basis,
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11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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12 * for the specific language governing rights and limitations under the
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13 * License.
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14 *
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15 * The Original Code is the Dynamin library.
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16 *
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17 * The Initial Developer of the Original Code is Jordan Miner.
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18 * Portions created by the Initial Developer are Copyright (C) 2006-2009
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19 * the Initial Developer. All Rights Reserved.
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20 *
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21 * Contributor(s):
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22 * Jordan Miner <jminer7@gmail.com>
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23 *
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24 */
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25
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26 module dynamin.core.environment;
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27
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28 import dynamin.all_core;
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29 import dynamin.core_backend;
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30
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31 /**
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32 * Contains static methods to access information about the computer the
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33 * application is running on.
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34 */
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35 static class Environment {
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36 static:
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37 private:
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38 mixin EnvironmentBackend;
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39 public:
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40 /**
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41 * Returns the time in milliseconds since the program was started.
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42 * On Windows XP, this time is updated every millisecond.
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43 * On Linux, this time is usually updated every millisecond, but
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44 * occasionally may take 5 to 10 milliseconds.
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45 * This is the author's dream time function because
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46 *
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47 * $(OL
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48 * $(LI It is accurate to 1 millisecond.)
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49 * $(LI It works correctly on multiple core computers.)
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50 * $(LI It is unaffected by changes to the system time.)
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51 * $(LI It never wraps to zero.)
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52 * )
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53 *
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54 * On my 1.3 GHz celeron, this function can be called about 480 times
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55 * in one millisecond under Windows and about 380 times in one millisecond
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56 * under Linux.
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57 *
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58 * TODO: make sure it works with multiple cores, although I'm sure it does
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59 */
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60 long runningTime() {
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61 return backend_runningTime;
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62 }
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63 /**
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64 * Returns the system time in milliseconds since January 1, 1970 UTC.
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65 * On Windows XP, this time is only updated every 15.625 milliseconds.
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66 *
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67 * On my 1.3 GHz celeron, this function can be called about 12,000 times
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68 * in one millisecond under Windows and about 460 times in one millisecond
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69 * under Linux.
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70 */
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71 long systemTime() {
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72 return backend_systemTime;
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73 }
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74 /**
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75 * Gets the number of logical processors on this computer. A logical
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76 * processor can either be a different physical processor or simply
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77 * another core in the same processor. Even a single core hyper-threaded
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78 * processor is considered to have two logical processors.
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79 * Returns: the number of logical processors
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80 */
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81 int processorCount() {
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82 return backend_processorCount;
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83 }
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84 /**
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85 * The number returned by this method can be used to measure the
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86 * time between two calls. This method uses the highest resolution
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87 * timer available.
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88 *
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89 * On my 1.3 GHz celeron, this function can be called about 500 times
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90 * in one millisecond under Windows.
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91 *
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92 * Returns: the current time in milliseconds
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93 *
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94 * Note: Under Windows, this is implemented using QueryPerformanceCounter().
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95 * QueryPerformanceCounter() gets the time counter from the processor.
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96 * On processors with multiple cores (such as an Althon X2 or a Core 2 Duo),
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97 * the time counter for each core may be a few milliseconds different.
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98 * (Microsoft's documentation says this is due to bugs in the BIOS or HAL.)
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99 * Since QueryPerformanceCounter() can get the time from either core,
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100 * the time between two calls made within the same millisecond can be off.
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101 * For example, on my Althon X2 computer, the difference between cores
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102 * is usually 60 ms. If two calls to QueryPerformanceCounter() are made
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103 * in the same millisecond, there is a possiblity that the second one
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104 * will return a time 60 ms smaller than the first.
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105 * Under Linux, this is implemented using gettimeofday(), which has no
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106 * problems with multiple cores and is accurate.
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107 * One way to fix this inaccuracy is by only allowing the thread to
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108 * use one processor. Another problem is that this time will run slightly
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109 * faster or slower than the system time.
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110 */
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111 private long processorTime() {
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112 return backend_processorTime;
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113 }
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114 }
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115
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116 unittest {
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117 auto startTime = Environment.runningTime;
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118 assert(startTime > 0);
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119 auto time = startTime;
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120 const SAMPLE = 50;
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121 // makes sure that RunningTime does not go backwards
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122 for(int i = 0; i < SAMPLE;) {
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123 auto time2 = Environment.runningTime;
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124 assert(time2 >= time);
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125 if(time2 > time) {
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126 time = time2;
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127 ++i;
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128 }
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129 }
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130 //printf("avg accuracy: %.1f ms\n", (time-startTime)/cast(float)SAMPLE);
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131 }
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132
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