我们运行程序的时候，可以简单使用clock函数测试程序的运行时间：（本示例中以微秒为单位输出）
https://github.com/yaowenxu/Workplace/blob/master/timer/clocktimer.c
代码语言：javascript复制/**
* Author: Yaowen Xu
* Github: https://github.com/yaowenxu
* Organization: 北航系统结构研究所
* Date: 2019-08-18 11:59:54
* LastEditTime: 2019-08-18 12:45:45
* Description: 使用 C 语言标准库函数clock来进行测试程序运行时间
*/
#include <time.h>
#include <stdio.h>
#include <math.h>
int str2int(char* str){
char *p = str;
int sum = 0;
while (*p != ' ')
{
sum = sum*10 (*p-'0');
p ;
}
return sum;
}
int main(int argc, char* argv[]){
clock_t start, stop;
int def = 1000;
if (argc == 2)
{
def = str2int(argv[argc-1]);
}
start = clock();
for (int i = 0; i < def ; i )
{
float tmp = sqrt(i);
}
stop = clock();
double total = stop - start; // 使用运行的时间
printf("Clocks: %.1fn", total); // 总共使用的时钟
printf("Time: %.1f usn", total*1e6/(CLOCKS_PER_SEC)); // 转换运行时间为微秒
return 0;
}
/*
* Approximates the processor time used by the program,
* since the beginning of an implementation-defined time
* period that is related to the program invocation.
* To measure the time spent in a program, call the clock()
* function at the start of the program, and subtract its
* returned value from the value returned by subsequent calls
* to clock(). Then, to obtain the time in seconds, divide
* the value returned by clock() by CLOCKS_PER_SEC.
*
* If you use the system() function in your program, do not
* rely on clock() for program timing, because calls to system()
* may reset the clock.
*
* In a multithread POSIX C application, if you are creating threads
* with a function that is based on a POSIX.4a draft standard,
* the clock() function is thread-scoped.
*
* Refer：https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.bpxbd00/clock.htm
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