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)
/** * 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 != '\0') { 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: %.1f\n", total); // 总共使用的时钟 printf("Time: %.1f us\n", 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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