Linux 下使用clock_gettime給程式計時詳解

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Linux 下使用clock_gettime給程式計時詳解,函數的原型如下:

int clock_gettime(clockid_t clk_id,
struct timespect
*tp);

clockid_t
clk_id用於指定計時時鐘的類型,對於我們Programmr以下三種比較常用:

CLOCK_REALTIME, a system-wide realtime clock.CLOCK_PROCESS_CPUTIME_ID, high-resolution timer provided by the CPU for each process.CLOCK_THREAD_CPUTIME_ID, high-resolution timer provided by the CPU for each of the threads.
  1. CLOCK_REALTIME:系統即時時間,隨系統即時時間改變而改變,即從UTC1970-1-1 0:0:0開始計時,中間時刻如果系統時間被使用者該成其他,則對應的時間相應改變  
  2.         CLOCK_MONOTONIC:從系統啟動這一刻起開始計時,不受系統時間被使用者改變的影響  
  3.         CLOCK_PROCESS_CPUTIME_ID:本進程到當前代碼系統CPU花費的時間  
  4.         CLOCK_THREAD_CPUTIME_ID:本線程到當前代碼系統CPU花費的時間 


CLOCK_REALTIME
, a system-wide realtime clock.CLOCK_PROCESS_CPUTIME_ID, high-resolution timer provided by the CPU for each process.CLOCK_THREAD_CPUTIME_ID, high-resolution timer provided by the CPU for each of the threads.struct timespect
*tp用來儲存當前的時間,其結
構如下:

1 struct timespec {
2 time_t tv_sec;
/* seconds
*/
3 long tv_nsec;
/* nanoseconds
*/
4 };

下面我們就上代碼把;


代碼1 #include
<iostream>
2 #include
<time.h>
3  using
namespace std;
4
5 timespec diff(timespec start, timespec end);
6
7  int main()
8 {
9 timespec time1, time2;
10 int temp;
11 clock_gettime(CLOCK_PROCESS_CPUTIME_ID,
&time1);
12 for (int i
= 0; i<
242000000; i++)
13 temp+=temp;
14 clock_gettime(CLOCK_PROCESS_CPUTIME_ID,
&time2);
15 cout<<diff(time1,time2).tv_sec<<":"<<diff(time1,time2).tv_nsec<<endl;
16 return
0;
17 }
18
19 timespec diff(timespec start, timespec end)
20 {
21 timespec temp;
22 if ((end.tv_nsec-start.tv_nsec)<0)
{
23 temp.tv_sec
= end.tv_sec-start.tv_sec-1;
24 temp.tv_nsec
= 1000000000+end.tv_nsec-start.tv_nsec;
25 }
else {
26 temp.tv_sec
= end.tv_sec-start.tv_sec;
27 temp.tv_nsec
= end.tv_nsec-start.tv_nsec;
28 }
29 return temp;
30 }
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