c - 如何测试不同算法的效率

Question

如何测试不同算法的效率，比如排序算法？我尝试使用 clock_gettime。它准确吗？有什么办法可以解决这个问题吗？

#include <stdio.h>
#include <sys/time.h>
#include <time.h>

/* compute interval: end - start */
struct timespec diff(struct timespec start, struct timespec end);

/* tested algorithm, just an example. Print 10000 lines "hello" */ 
void testFunc(void);

int main(void)
{
    struct timespec start;
    struct timespec end;

    struct timespec interval ;

    clock_gettime(CLOCK_REALTIME, &start);

    /* call the tested algorithm */
    testFunc();

    clock_gettime(CLOCK_REALTIME, &end);

    interval = diff(start, end);
    printf("%lld.%.9ld(seconds)\n", (long long)interval.tv_sec, interval.tv_nsec);

    return 0;
}

/* compute interval: end - start */
struct timespec diff(struct timespec start, struct timespec end)
{
    struct timespec temp;

    if ((end.tv_nsec - start.tv_nsec) < 0) {
        temp.tv_sec = end.tv_sec - start.tv_sec - 1;
        temp.tv_nsec = 1000000000 + end.tv_nsec - start.tv_nsec;
    } 
    else {
        temp.tv_sec = end.tv_sec - start.tv_sec;
        temp.tv_nsec = end.tv_nsec - start.tv_nsec;
    }

    return temp;
}

/* tested algorithm, just an example. Print 10000 lines "hello" */
void testFunc(void)
{
    int i;

    for (i = 0; i < 10000; i++) {
        printf("hello\n");
    }
}

Answer 1

您可以使用time 命令。可以找到很好的解释here .首先将源代码编译成可执行的二进制文件。然后运行 ​​time ./executable_code 并且不要根据一两个测试做出决定。祝你好运!