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  • 程序运行时间测试

    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

    /**
     * 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: %.1f
    ", total); // 总共使用的时钟
        printf("Time: %.1f us
    ", 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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  • 原文地址:https://www.cnblogs.com/xuyaowen/p/c-lib-clock.html
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