Linux下使用clock_gettime给程序计时 转载

http://www.cnblogs.com/daqiwancheng/archive/2010/07/01/1769522.html

Linux下使用clock_gettime给程序计时

   哦，clock_gettime( ) 提供了纳秒的精确度，给程序计时可是不错哦；
 
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, 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 };

呵呵，好啦！该讲的都刚清楚了，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 }