Mercurial > projects > dynamin
annotate dynamin/core/environment.d @ 103:73060bc3f004
Change license to Boost 1.0 and MPL 2.0.
| author | Jordan Miner <jminer7@gmail.com> |
|---|---|
| date | Tue, 15 May 2012 22:06:02 -0500 |
| parents | aa4efef0f0b1 |
| children | acdbb30fee7e |
| rev | line source |
|---|---|
| 0 | 1 |
| 2 /* | |
|
103
73060bc3f004
Change license to Boost 1.0 and MPL 2.0.
Jordan Miner <jminer7@gmail.com>
parents:
0
diff
changeset
|
3 * Copyright Jordan Miner |
| 0 | 4 * |
|
103
73060bc3f004
Change license to Boost 1.0 and MPL 2.0.
Jordan Miner <jminer7@gmail.com>
parents:
0
diff
changeset
|
5 * Distributed under the Boost Software License, Version 1.0. |
|
73060bc3f004
Change license to Boost 1.0 and MPL 2.0.
Jordan Miner <jminer7@gmail.com>
parents:
0
diff
changeset
|
6 * (See accompanying file BOOST_LICENSE.txt or copy at |
|
73060bc3f004
Change license to Boost 1.0 and MPL 2.0.
Jordan Miner <jminer7@gmail.com>
parents:
0
diff
changeset
|
7 * http://www.boost.org/LICENSE_1_0.txt) |
| 0 | 8 * |
| 9 */ | |
| 10 | |
| 11 module dynamin.core.environment; | |
| 12 | |
| 13 import dynamin.all_core; | |
| 14 import dynamin.core_backend; | |
| 15 | |
| 16 /** | |
| 17 * Contains static methods to access information about the computer the | |
| 18 * application is running on. | |
| 19 */ | |
| 20 static class Environment { | |
| 21 static: | |
| 22 private: | |
| 23 mixin EnvironmentBackend; | |
| 24 public: | |
| 25 /** | |
| 26 * Returns the time in milliseconds since the program was started. | |
| 27 * On Windows XP, this time is updated every millisecond. | |
| 28 * On Linux, this time is usually updated every millisecond, but | |
| 29 * occasionally may take 5 to 10 milliseconds. | |
| 30 * This is the author's dream time function because | |
| 31 * | |
| 32 * $(OL | |
| 33 * $(LI It is accurate to 1 millisecond.) | |
| 34 * $(LI It works correctly on multiple core computers.) | |
| 35 * $(LI It is unaffected by changes to the system time.) | |
| 36 * $(LI It never wraps to zero.) | |
| 37 * ) | |
| 38 * | |
| 39 * On my 1.3 GHz celeron, this function can be called about 480 times | |
| 40 * in one millisecond under Windows and about 380 times in one millisecond | |
| 41 * under Linux. | |
| 42 * | |
| 43 * TODO: make sure it works with multiple cores, although I'm sure it does | |
| 44 */ | |
| 45 long runningTime() { | |
| 46 return backend_runningTime; | |
| 47 } | |
| 48 /** | |
| 49 * Returns the system time in milliseconds since January 1, 1970 UTC. | |
| 50 * On Windows XP, this time is only updated every 15.625 milliseconds. | |
| 51 * | |
| 52 * On my 1.3 GHz celeron, this function can be called about 12,000 times | |
| 53 * in one millisecond under Windows and about 460 times in one millisecond | |
| 54 * under Linux. | |
| 55 */ | |
| 56 long systemTime() { | |
| 57 return backend_systemTime; | |
| 58 } | |
| 59 /** | |
| 60 * Gets the number of logical processors on this computer. A logical | |
| 61 * processor can either be a different physical processor or simply | |
| 62 * another core in the same processor. Even a single core hyper-threaded | |
| 63 * processor is considered to have two logical processors. | |
| 64 * Returns: the number of logical processors | |
| 65 */ | |
| 66 int processorCount() { | |
| 67 return backend_processorCount; | |
| 68 } | |
| 69 /** | |
| 70 * The number returned by this method can be used to measure the | |
| 71 * time between two calls. This method uses the highest resolution | |
| 72 * timer available. | |
| 73 * | |
| 74 * On my 1.3 GHz celeron, this function can be called about 500 times | |
| 75 * in one millisecond under Windows. | |
| 76 * | |
| 77 * Returns: the current time in milliseconds | |
| 78 * | |
| 79 * Note: Under Windows, this is implemented using QueryPerformanceCounter(). | |
| 80 * QueryPerformanceCounter() gets the time counter from the processor. | |
| 81 * On processors with multiple cores (such as an Althon X2 or a Core 2 Duo), | |
| 82 * the time counter for each core may be a few milliseconds different. | |
| 83 * (Microsoft's documentation says this is due to bugs in the BIOS or HAL.) | |
| 84 * Since QueryPerformanceCounter() can get the time from either core, | |
| 85 * the time between two calls made within the same millisecond can be off. | |
| 86 * For example, on my Althon X2 computer, the difference between cores | |
| 87 * is usually 60 ms. If two calls to QueryPerformanceCounter() are made | |
| 88 * in the same millisecond, there is a possiblity that the second one | |
| 89 * will return a time 60 ms smaller than the first. | |
| 90 * Under Linux, this is implemented using gettimeofday(), which has no | |
| 91 * problems with multiple cores and is accurate. | |
| 92 * One way to fix this inaccuracy is by only allowing the thread to | |
| 93 * use one processor. Another problem is that this time will run slightly | |
| 94 * faster or slower than the system time. | |
| 95 */ | |
| 96 private long processorTime() { | |
| 97 return backend_processorTime; | |
| 98 } | |
| 99 } | |
| 100 | |
| 101 unittest { | |
| 102 auto startTime = Environment.runningTime; | |
| 103 assert(startTime > 0); | |
| 104 auto time = startTime; | |
| 105 const SAMPLE = 50; | |
| 106 // makes sure that RunningTime does not go backwards | |
| 107 for(int i = 0; i < SAMPLE;) { | |
| 108 auto time2 = Environment.runningTime; | |
| 109 assert(time2 >= time); | |
| 110 if(time2 > time) { | |
| 111 time = time2; | |
| 112 ++i; | |
| 113 } | |
| 114 } | |
| 115 //printf("avg accuracy: %.1f ms\n", (time-startTime)/cast(float)SAMPLE); | |
| 116 } | |
| 117 |