The accuracy test of Win32 function sleep

In three ways, the first uses high-precision performance counters, the second is the use of multimedia timers, and the other is the CPU cycles provided in Windows graphics programming. The first method of measurement is recommended:

Let's look at the first type:

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2. #include <windows.h>
4. #include <stdio.h>
8. void Main ()
10. {
12. Large_integer litmp;
14. Longlong Qt1,qt2;
16. double DFT,DFF,DFM;
20. //Get clock frequency
22. QueryPerformanceFrequency (&LITMP); //Get clock frequency
24. dff= (double) litmp.  QuadPart;
28. //Get initial value
30. QueryPerformanceCounter (&LITMP);
32. Qt1=litmp. QuadPart;
36. //below some time-consuming operations
38. Sleep (1);
42. //Get termination value
44. QueryPerformanceCounter (&LITMP);
46. Qt2=litmp. QuadPart;
50. //Get the corresponding time value, go to the millisecond unit
52. Dfm= (Double) (QT2-QT1);
54. DFT=DFM/DFF;
60. printf ("spents:%.3f milliseconds \ n", dft*1000.0);
62. }

On my machine for Sleep (1) = 0.454ms;sleep (Ten) = 9.719ms;sleep (+) = 99.541ms

Here are two other options for reference:

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2. #include <stdio.h>
4. #include <Windows.h>
6. #include <Mmsystem.h>
8. #include "Timer.h"
12. #pragma comment (lib, "Winmm.lib")
18. int i = 0;
20. DWORD start;
22. DWORD end;
26. #define TIMES (1000)
30. void Main ()
32. {
34. ////////////////////////////////////////////////////////////////////////////////  
36. //  
38. //1. Initialize with a high-precision timer
40. //  
42. //high-precision timer initialization
44. //NOTE: If you do not execute the following statement initialized to 1ms, the precision of sleep () will be affected
46. :: Timebeginperiod (1);
48. Sleep (100);
52. //Start timing
54. Start =:: timeGetTime ();
56. For (i=0; i<times; i++)//cumulative test
58. {
60. Sleep (1);
62. }
66. //End Timing
68. End =:: timeGetTime ();
70. printf ("Use a high-precision timer to test sleep (1) Time:%.3f ms\n", (End-start)/((Double) times));
80. ////////////////////////////////////////////////////////////////////////////////  
82. //  
84. //2. Using the number of CPU cycles to get
86. //  
88. Ktimer timer;
92. ///below to get CPU speed (MHZ)
94. Timer. Start ();
96. Sleep (1000);
98. unsigned __int64 cpuspeed = (unsigned) (timer.  Stop ()/1000000);
100. printf ("CPU speed:%i64d mhz\n", cpuspeed);
106. //Start testing
108. Timer. Start ();
112. Sleep (1);
116. //End
118. unsigned __int64 time = (unsigned) timer.  Stop ();
120. printf ("sleep (1) time measured with CPU cycles:%i64dμs\n", time/cpuspeed);
126. //  
128. //After the test is completed, the timing accuracy is recalled
130. //  
132. :: Timeendperiod (1);
138. }

The accuracy test of Win32 function sleep