Дебажил свой код, в итоге обнаружил следующее: Thread.sleep(Timeout) выполняется с низкой точностью (и решил поделиться с общественностью). Для проверки точности измерений Thread.sleep(Timeout) был написан вот этот кусок кода: | Код |
timer = System.currentTimeMillis();// замеряем текущее время.
Thread.sleep(Timeout);// спим %Timeout% ms.
diff = (System.currentTimeMillis() - timer); // считаем сколько
// реально
// проспали.
|
Затем оно прогонялся поочерёдно для Timeout= 1, 2, 3, ... Как показал тест под Windows: Thread.sleep(Timeout); проспит С БОЛЬШОЙ ВЕРОЯТНОСТЬЮ (больше 90%) заданное время (Timeout) если заданное время кратно 15 миллисекундам, либо больше 100 миллисекунд. Весь код: | Код |
package test;
public class Msec {
/**
* @param args
* @throws InterruptedException
*/
static long timer;
static long Timeout;
static long diff;
static int Measurements = 100;
static double average = 0;
static long max = 0;
static long maxdiff = 0;
private static double v;
public static void main(String[] args) throws InterruptedException {
System.out.println("measurements: " + (Measurements) + ""); // количество
// замеров
System.out.println();
for (int j = 1; j < 10000; j = j + 1) {
Timeout = j; // Выбираем таймаут для тестирования
max = 0;
maxdiff = 0;
for (int k = 0; k < Measurements; k++)// выполняем %Measurements%
// замеров
{
System.gc(); // Чистим память.
timer = System.currentTimeMillis();// замеряем текущее время.
Thread.sleep(Timeout);// спим %Timeout% ms.
diff = (System.currentTimeMillis() - timer); // считаем сколько
// реально
// проспали.
if (Math.abs(diff - Timeout) > Math.abs(max)) {
max = (diff - Timeout); // Регистрируем максимальное
// отклонение
maxdiff = diff; // Регистрируем значение дающее максимальное
// отклонение
}
average = average + Math.abs(diff - Timeout); // накапливаем
// отклонения
}
average = average / Measurements; // Итого. Считаем среднее
// отклонение.
//printFullStats(); //Печатаем подробную статистику
printShortStats(); //Печатаем только качество для заданного таймаута
}
}
private static void printFullStats() {
System.out
.println("--------------------------------------------------");
System.out.println("tested timeout = [" + Timeout + "] ms ");
// TODO Auto-generated method stub
System.out.println(" max bad value: " + (maxdiff) + "ms"); // значение
// дающее
// максимальное
// отклонение
System.out.println(" max difference: " + (max) + "ms"); // максимальное
// отклонение
System.out.println(" %: "
+ ((int) (10000 * (max) / Timeout) / 100.0)); // максимальное
// отклонение
// %
System.out.println(" average diff: "
+ (((int) (100 * average)) / 100.0) + "ms"); // среднее
// отклонение
System.out.println(" %: "
+ ((int) (10000 * (average) / Timeout) / 100.0)); // среднее
// отклонение
// %
}
private static void printShortStats() throws InterruptedException {
v = ((int) (10000 * (average) / Timeout) / 100.0);
if (v >= 10) {
System.out
.println("--------------------------------------------------");
System.out.println("tested timeout = [" + Timeout + "] ms ");
System.out.println(" quailty %: " + v);
} else {
System.err
.println("--------------------------------------------------");
System.err.println("tested timeout = [" + Timeout + "] ms ");
System.err.println(" quailty %: " + v);
Thread.sleep(100);
}
}
}
|
Лог: | Код |
measurements: 100
--------------------------------------------------
tested timout = [1] ms
quailty %: 304.0
--------------------------------------------------
tested timout = [2] ms
quailty %: 194.52
--------------------------------------------------
tested timout = [3] ms
quailty %: 188.63
--------------------------------------------------
tested timout = [4] ms
quailty %: 163.91
--------------------------------------------------
tested timout = [5] ms
quailty %: 164.11
--------------------------------------------------
tested timout = [6] ms
quailty %: 129.2
--------------------------------------------------
tested timout = [7] ms
quailty %: 113.25
--------------------------------------------------
tested timout = [8] ms
quailty %: 98.11
--------------------------------------------------
tested timout = [9] ms
quailty %: 82.42
--------------------------------------------------
tested timout = [10] ms
quailty %: 73.54
--------------------------------------------------
tested timout = [11] ms
quailty %: 59.03
--------------------------------------------------
tested timout = [12] ms
quailty %: 41.79
--------------------------------------------------
tested timout = [13] ms
quailty %: 32.0
--------------------------------------------------
tested timout = [14] ms
quailty %: 19.72
--------------------------------------------------
tested timout = [15] ms
quailty %: 4.51
--------------------------------------------------
tested timout = [16] ms
quailty %: 12.6
--------------------------------------------------
tested timout = [17] ms
quailty %: 18.0
--------------------------------------------------
tested timout = [18] ms
quailty %: 26.0
--------------------------------------------------
tested timout = [19] ms
quailty %: 30.77
--------------------------------------------------
tested timout = [20] ms
quailty %: 29.09
--------------------------------------------------
tested timout = [21] ms
quailty %: 34.51
--------------------------------------------------
tested timout = [22] ms
quailty %: 34.96
--------------------------------------------------
tested timout = [23] ms
quailty %: 34.29
--------------------------------------------------
tested timout = [24] ms
quailty %: 32.32
--------------------------------------------------
tested timout = [25] ms
quailty %: 37.27
--------------------------------------------------
tested timout = [26] ms
quailty %: 26.12
--------------------------------------------------
tested timout = [27] ms
quailty %: 22.06
--------------------------------------------------
tested timout = [28] ms
quailty %: 15.74
--------------------------------------------------
tested timout = [29] ms
quailty %: 12.6
--------------------------------------------------
tested timout = [30] ms
quailty %: 6.78
--------------------------------------------------
tested timout = [31] ms
quailty %: 1.87
--------------------------------------------------
tested timout = [32] ms
quailty %: 5.08
--------------------------------------------------
tested timout = [33] ms
quailty %: 9.71
--------------------------------------------------
tested timout = [34] ms
quailty %: 13.27
--------------------------------------------------
tested timout = [35] ms
quailty %: 17.3
--------------------------------------------------
tested timout = [36] ms
quailty %: 17.86
--------------------------------------------------
tested timout = [37] ms
quailty %: 20.2
--------------------------------------------------
tested timout = [38] ms
quailty %: 20.35
--------------------------------------------------
tested timout = [39] ms
quailty %: 19.96
--------------------------------------------------
tested timout = [40] ms
quailty %: 19.54
--------------------------------------------------
tested timout = [41] ms
quailty %: 17.82
--------------------------------------------------
tested timout = [42] ms
quailty %: 15.07
--------------------------------------------------
tested timout = [43] ms
quailty %: 14.47
--------------------------------------------------
tested timout = [44] ms
quailty %: 9.59
--------------------------------------------------
tested timout = [45] ms
quailty %: 6.49
--------------------------------------------------
tested timout = [46] ms
quailty %: 1.97
--------------------------------------------------
tested timout = [47] ms
quailty %: 5.21
--------------------------------------------------
tested timout = [48] ms
quailty %: 5.96
--------------------------------------------------
tested timout = [49] ms
quailty %: 9.54
--------------------------------------------------
tested timout = [50] ms
quailty %: 11.39
--------------------------------------------------
tested timout = [51] ms
quailty %: 11.38
--------------------------------------------------
tested timout = [52] ms
quailty %: 13.93
--------------------------------------------------
tested timout = [53] ms
quailty %: 14.53
--------------------------------------------------
tested timout = [54] ms
quailty %: 14.53
--------------------------------------------------
tested timout = [55] ms
quailty %: 14.34
--------------------------------------------------
tested timout = [56] ms
quailty %: 13.71
--------------------------------------------------
tested timout = [57] ms
quailty %: 11.85
--------------------------------------------------
tested timout = [58] ms
quailty %: 9.96
--------------------------------------------------
tested timout = [59] ms
quailty %: 8.92
--------------------------------------------------
tested timout = [60] ms
quailty %: 6.12
--------------------------------------------------
tested timout = [61] ms
quailty %: 3.71
--------------------------------------------------
tested timout = [62] ms
quailty %: 0.9
--------------------------------------------------
tested timout = [63] ms
quailty %: 2.12
--------------------------------------------------
tested timout = [64] ms
quailty %: 4.0
--------------------------------------------------
tested timout = [65] ms
quailty %: 7.77
--------------------------------------------------
tested timout = [66] ms
quailty %: 9.06
--------------------------------------------------
tested timout = [67] ms
quailty %: 9.7
--------------------------------------------------
tested timout = [68] ms
quailty %: 10.86
--------------------------------------------------
tested timout = [69] ms
quailty %: 11.17
--------------------------------------------------
tested timout = [70] ms
quailty %: 11.16
--------------------------------------------------
tested timout = [71] ms
quailty %: 10.87
--------------------------------------------------
tested timout = [72] ms
quailty %: 10.75
--------------------------------------------------
tested timout = [73] ms
quailty %: 10.51
--------------------------------------------------
tested timout = [74] ms
quailty %: 8.68
--------------------------------------------------
tested timout = [75] ms
quailty %: 7.2
--------------------------------------------------
tested timout = [76] ms
quailty %: 4.66
--------------------------------------------------
tested timout = [77] ms
quailty %: 2.69
--------------------------------------------------
tested timout = [78] ms
quailty %: 0.19
--------------------------------------------------
tested timout = [79] ms
quailty %: 2.21
--------------------------------------------------
tested timout = [80] ms
quailty %: 4.42
--------------------------------------------------
tested timout = [81] ms
quailty %: 5.67
--------------------------------------------------
tested timout = [82] ms
quailty %: 8.28
--------------------------------------------------
tested timout = [83] ms
quailty %: 8.75
--------------------------------------------------
tested timout = [84] ms
quailty %: 8.97
--------------------------------------------------
tested timout = [85] ms
quailty %: 9.25
--------------------------------------------------
tested timout = [86] ms
quailty %: 9.18
--------------------------------------------------
tested timout = [87] ms
quailty %: 8.65
--------------------------------------------------
tested timout = [88] ms
quailty %: 7.98
--------------------------------------------------
tested timout = [89] ms
quailty %: 6.5
--------------------------------------------------
tested timout = [90] ms
quailty %: 5.86
--------------------------------------------------
tested timout = [91] ms
quailty %: 4.65
--------------------------------------------------
tested timout = [92] ms
quailty %: 2.98
--------------------------------------------------
tested timout = [93] ms
quailty %: 1.18
--------------------------------------------------
tested timout = [94] ms
quailty %: 1.71
--------------------------------------------------
tested timout = [95] ms
quailty %: 2.97
--------------------------------------------------
tested timout = [96] ms
quailty %: 5.25
--------------------------------------------------
tested timout = [97] ms
quailty %: 6.52
--------------------------------------------------
tested timout = [98] ms
quailty %: 6.81
--------------------------------------------------
tested timout = [99] ms
quailty %: 7.43
--------------------------------------------------
tested timout = [100] ms
quailty %: 7.73
--------------------------------------------------
tested timout = [101] ms
quailty %: 7.72
--------------------------------------------------
tested timout = [102] ms
quailty %: 7.68
--------------------------------------------------
tested timout = [103] ms
quailty %: 7.25
--------------------------------------------------
tested timout = [104] ms
quailty %: 6.41
--------------------------------------------------
tested timout = [105] ms
quailty %: 5.65
--------------------------------------------------
tested timout = [106] ms
quailty %: 4.75
--------------------------------------------------
tested timout = [107] ms
quailty %: 3.49
--------------------------------------------------
tested timout = [108] ms
quailty %: 2.03
--------------------------------------------------
tested timout = [109] ms
quailty %: 0.36
--------------------------------------------------
tested timout = [110] ms
quailty %: 1.49
--------------------------------------------------
tested timout = [111] ms
quailty %: 2.67
--------------------------------------------------
tested timout = [112] ms
quailty %: 4.22
--------------------------------------------------
tested timout = [113] ms
quailty %: 5.05
--------------------------------------------------
tested timout = [114] ms
quailty %: 5.41
--------------------------------------------------
tested timout = [115] ms
quailty %: 6.26
--------------------------------------------------
tested timout = [116] ms
quailty %: 6.66
--------------------------------------------------
tested timout = [117] ms
quailty %: 6.76
--------------------------------------------------
tested timout = [118] ms
quailty %: 6.53
--------------------------------------------------
tested timout = [119] ms
quailty %: 6.39
--------------------------------------------------
tested timout = [120] ms
quailty %: 5.48
--------------------------------------------------
tested timout = [121] ms
quailty %: 4.78
--------------------------------------------------
tested timout = [122] ms
quailty %: 3.76
--------------------------------------------------
tested timout = [123] ms
quailty %: 3.0
--------------------------------------------------
tested timout = [124] ms
quailty %: 1.82
--------------------------------------------------
tested timout = [125] ms
quailty %: 0.14
--------------------------------------------------
tested timout = [126] ms
quailty %: 2.2
--------------------------------------------------
tested timout = [127] ms
quailty %: 3.24
--------------------------------------------------
tested timout = [128] ms
quailty %: 5.28
--------------------------------------------------
tested timout = [129] ms
quailty %: 5.7
--------------------------------------------------
tested timout = [130] ms
quailty %: 5.52
--------------------------------------------------
tested timout = [131] ms
quailty %: 5.86
--------------------------------------------------
tested timout = [132] ms
quailty %: 6.02
--------------------------------------------------
tested timout = [133] ms
quailty %: 5.91
--------------------------------------------------
tested timout = [134] ms
quailty %: 5.56
--------------------------------------------------
tested timout = [135] ms
quailty %: 5.29
--------------------------------------------------
tested timout = [136] ms
quailty %: 4.69
--------------------------------------------------
tested timout = [137] ms
quailty %: 3.42
--------------------------------------------------
tested timout = [138] ms
quailty %: 2.89
--------------------------------------------------
tested timout = [139] ms
quailty %: 1.66
--------------------------------------------------
tested timout = [140] ms
quailty %: 0.43
--------------------------------------------------
tested timout = [141] ms
quailty %: 1.23
--------------------------------------------------
tested timout = [142] ms
quailty %: 2.51
--------------------------------------------------
tested timout = [143] ms
quailty %: 2.62
|
--------------------
Если собака свернулась калачиком, значит будет дождь, а если сидит выпучив глаза, значит у неё запор. |
Thread.sleep(long t); точность замера 
Загрузка ...
