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Initial commit of code.
author Jordan Miner <jminer7@gmail.com>
date Mon, 15 Jun 2009 22:10:48 -0500
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1 // Written in the D programming language
2 // www.digitalmars.com/d/
3
4 /*
5 * The contents of this file are subject to the Mozilla Public License Version
6 * 1.1 (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 * http://www.mozilla.org/MPL/
9 *
10 * Software distributed under the License is distributed on an "AS IS" basis,
11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 * for the specific language governing rights and limitations under the
13 * License.
14 *
15 * The Original Code is the Dynamin library.
16 *
17 * The Initial Developer of the Original Code is Jordan Miner.
18 * Portions created by the Initial Developer are Copyright (C) 2006-2009
19 * the Initial Developer. All Rights Reserved.
20 *
21 * Contributor(s):
22 * Jordan Miner <jminer7@gmail.com>
23 *
24 */
25
26 module dynamin.core.environment;
27
28 import dynamin.all_core;
29 import dynamin.core_backend;
30
31 /**
32 * Contains static methods to access information about the computer the
33 * application is running on.
34 */
35 static class Environment {
36 static:
37 private:
38 mixin EnvironmentBackend;
39 public:
40 /**
41 * Returns the time in milliseconds since the program was started.
42 * On Windows XP, this time is updated every millisecond.
43 * On Linux, this time is usually updated every millisecond, but
44 * occasionally may take 5 to 10 milliseconds.
45 * This is the author's dream time function because
46 *
47 * $(OL
48 * $(LI It is accurate to 1 millisecond.)
49 * $(LI It works correctly on multiple core computers.)
50 * $(LI It is unaffected by changes to the system time.)
51 * $(LI It never wraps to zero.)
52 * )
53 *
54 * On my 1.3 GHz celeron, this function can be called about 480 times
55 * in one millisecond under Windows and about 380 times in one millisecond
56 * under Linux.
57 *
58 * TODO: make sure it works with multiple cores, although I'm sure it does
59 */
60 long runningTime() {
61 return backend_runningTime;
62 }
63 /**
64 * Returns the system time in milliseconds since January 1, 1970 UTC.
65 * On Windows XP, this time is only updated every 15.625 milliseconds.
66 *
67 * On my 1.3 GHz celeron, this function can be called about 12,000 times
68 * in one millisecond under Windows and about 460 times in one millisecond
69 * under Linux.
70 */
71 long systemTime() {
72 return backend_systemTime;
73 }
74 /**
75 * Gets the number of logical processors on this computer. A logical
76 * processor can either be a different physical processor or simply
77 * another core in the same processor. Even a single core hyper-threaded
78 * processor is considered to have two logical processors.
79 * Returns: the number of logical processors
80 */
81 int processorCount() {
82 return backend_processorCount;
83 }
84 /**
85 * The number returned by this method can be used to measure the
86 * time between two calls. This method uses the highest resolution
87 * timer available.
88 *
89 * On my 1.3 GHz celeron, this function can be called about 500 times
90 * in one millisecond under Windows.
91 *
92 * Returns: the current time in milliseconds
93 *
94 * Note: Under Windows, this is implemented using QueryPerformanceCounter().
95 * QueryPerformanceCounter() gets the time counter from the processor.
96 * On processors with multiple cores (such as an Althon X2 or a Core 2 Duo),
97 * the time counter for each core may be a few milliseconds different.
98 * (Microsoft's documentation says this is due to bugs in the BIOS or HAL.)
99 * Since QueryPerformanceCounter() can get the time from either core,
100 * the time between two calls made within the same millisecond can be off.
101 * For example, on my Althon X2 computer, the difference between cores
102 * is usually 60 ms. If two calls to QueryPerformanceCounter() are made
103 * in the same millisecond, there is a possiblity that the second one
104 * will return a time 60 ms smaller than the first.
105 * Under Linux, this is implemented using gettimeofday(), which has no
106 * problems with multiple cores and is accurate.
107 * One way to fix this inaccuracy is by only allowing the thread to
108 * use one processor. Another problem is that this time will run slightly
109 * faster or slower than the system time.
110 */
111 private long processorTime() {
112 return backend_processorTime;
113 }
114 }
115
116 unittest {
117 auto startTime = Environment.runningTime;
118 assert(startTime > 0);
119 auto time = startTime;
120 const SAMPLE = 50;
121 // makes sure that RunningTime does not go backwards
122 for(int i = 0; i < SAMPLE;) {
123 auto time2 = Environment.runningTime;
124 assert(time2 >= time);
125 if(time2 > time) {
126 time = time2;
127 ++i;
128 }
129 }
130 //printf("avg accuracy: %.1f ms\n", (time-startTime)/cast(float)SAMPLE);
131 }
132