Linux 下使用clock_gettime给程序计时详解

Linux 下使用clock_gettime给程序计时详解，函数的原型如下：

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

clockid_t

clk_id用于指定计时时钟的类型，对于我们Programmr以下三种比较常用：

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.

CLOCK_REALTIME:系统实时时间,随系统实时时间改变而改变,即从UTC1970-1-1 0:0:0开始计时,中间时刻如果系统时间被用户该成其他,则对应的时间相应改变
CLOCK_MONOTONIC:从系统启动这一刻起开始计时,不受系统时间被用户改变的影响
CLOCK_PROCESS_CPUTIME_ID:本进程到当前代码系统CPU花费的时间
CLOCK_THREAD_CPUTIME_ID:本线程到当前代码系统CPU花费的时间



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用来存储当前的时间，其结

构如下：

1 struct timespec {

2 time_t tv_sec;
/* seconds
*/

3 long tv_nsec;
/* nanoseconds
*/

4 };

下面我们就上代码把；


代码

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 }