Linux下使用clock_gettime给程序计时

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 */
};代码；#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 }