原创 Linux下使用clock_gettime给程序计时

 2011-1-8 20:23  2553 6 6 分类: 工程师职场

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>
#include <time.h>
 using namespace std;

timespec diff(timespec start, timespec end);

 int main()
{
   timespec time1, time2;
   int temp;
   clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);
   for (int i = 0; i< 242000000; i++)
       temp+=temp;
   clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time2);
   cout<<diff(time1,time2).tv_sec<<":"<<diff(time1,time2).tv_nsec<<endl;
   return 0;
}

timespec diff(timespec start, timespec end)
{
   timespec temp;
   if ((end.tv_nsec-start.tv_nsec)<0) {
       temp.tv_sec = end.tv_sec-start.tv_sec-1;
       temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
   } else {
       temp.tv_sec = end.tv_sec-start.tv_sec;
       temp.tv_nsec = end.tv_nsec-start.tv_nsec;
   }
   return temp;
}