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我制作了一个程序来展开循环并测量它对数组进行排序所花费的时间，但我遇到的问题是，有时展开的循环程序在纳秒内给我一个 0 的答案，而这是不可能的。我也用 MONOTONIC 试过，但没有帮助。这是我的代码：

    #include <stdio.h>
    #include <time.h>
    #include <stdlib.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <math.h>
    #include <unistd.h>
    #define BILLION  1000000000L
    int main()
    {
        char buf[500];
        int numberOfElements = 10;
        int currentTest = 1;
        int randomArray[numberOfElements];
        int minIndex;
        int minValue;
        struct timespec requestStart;
        struct timespec requestEnd;
        long int recordStartTime;
        long int recordEndTime;
        long int elapsedTime;
        FILE *arrangedArray;
        FILE *stopwatch;
        sprintf(buf,"place to store file/Stopwatch.txt", currentTest);
        stopwatch = fopen(buf, "a+");
        struct stat st = {0};
        sprintf(buf, "the place where you stored the stopwatch file", currentTest);
        if (stat(buf, &st) == -1)
        {
            sprintf(buf, "the place where you stored the stopwatch file", currentTest);
            mkdir(buf);
        }
        sprintf(buf, "the place where you store this program/ArrangedArray.txt", currentTest);
        arrangedArray = fopen(buf, "w+");
        randomArray[0] = 7045;

        randomArray[1] = 4949;

        randomArray[2] = 24507;

        randomArray[3] = 6071;

        randomArray[4] = 11820;

        randomArray[5] = 11710;

        randomArray[6] = 11168;

        randomArray[7] = 11234;

        randomArray[8] = 11863;

        randomArray[9] = 2683;

        clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &requestStart);
        recordStartTime = requestStart.tv_nsec + requestStart.tv_sec * BILLION;
        minIndex = 0;

        minIndex = 1;

        minIndex = 9;

        minValue = randomArray[9];

        randomArray[9] = randomArray[0];

        randomArray[0] = 2683;

        minIndex = 1;

        minIndex = 2;

        minIndex = 3;

        minValue = randomArray[3];

        randomArray[3] = randomArray[2];

        randomArray[2] = 6071;

        minIndex = 3;

        minIndex = 4;

        minIndex = 5;

        minIndex = 6;

        minIndex = 9;

        minValue = randomArray[9];

        randomArray[9] = randomArray[3];

        randomArray[3] = 7045;

        minIndex = 4;

        minIndex = 5;

        minIndex = 6;

        minValue = randomArray[6];

        randomArray[6] = randomArray[4];

        randomArray[4] = 11168;

        minIndex = 5;

        minIndex = 7;

        minValue = randomArray[7];

        randomArray[7] = randomArray[5];

        randomArray[5] = 11234;

        minIndex = 6;

        minIndex = 7;

        minValue = randomArray[7];

        randomArray[7] = randomArray[6];

        randomArray[6] = 11710;

        minIndex = 7;

        minIndex = 8;

        minIndex = 9;

        clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &requestEnd);
        recordEndTime = (requestEnd.tv_nsec + requestEnd.tv_sec * BILLION);
        elapsedTime = recordEndTime - recordStartTime;
        sprintf(buf, "%li\n", elapsedTime);
        fputs(buf, stopwatch);
        sprintf(buf, "%i\n", randomArray[0]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[1]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[2]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[3]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[4]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[5]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[6]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[7]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[8]);
        fputs(buf, arrangedArray);
        sprintf(buf, "%i\n", randomArray[9]);
        fputs(buf, arrangedArray);

        fclose(arrangedArray);
        fclose(stopwatch);
        return 0;
    }
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