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：

struct timespec {
time_t tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
};

呵呵，好啦！该讲的都刚清楚了，下面我们就上代码把；

代码

#include <iostream>
#include <time.h>
usingnamespace 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;
return0;
}

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;
}