time.h库不工作

Question

我在K&R书和练习3-1上。我想我的"time.h“库坏了。起初，我认为我的代码是错误的，但当我在网上检查练习的解决方案时，它们也不起作用。

问题是：

程序输出总是显示零秒，有时‘时钟’是交换的：

Output 1:
    Element -1 not found.
    binsearch() took 10000 clocks (0 seconds)
    Element -1 not found.
    binsearch2() took 20000 clocks (0 seconds)

Output 2:
    Element -1 not found.
    binsearch() took 20000 clocks (0 seconds)
    Element -1 not found.
    binsearch2() took 10000 clocks (0 seconds)

该程序的目的是在速度方面比较这两个函数。我该如何比较呢？

下面是测试代码：

 for ( i = 0, time_taken = clock(); i < 100000; ++i ) {
    index = binsearch(n, testdata, MAX_ELEMENT);   /* all this code is duplicated with a
}                                                     call to binsearch2 instead */
time_taken = clock() - time_taken;

if ( index < 0 )
    printf("Element %d not found.\n", n);
else
    printf("Element %d found at index %d.\n", n, index);

printf("binsearch() took %lu clocks (%lu seconds)\n",
       (unsigned long) time_taken,
       (unsigned long) time_taken / CLOCKS_PER_SEC);

我在Linux和Windows上都尝试过这个程序。

Answer 1

也许是你系统里的CLOCKS_PER_SEC=1000000。

所以time_taken/CLOCKS_PER_SEC不出所料地给出了0。

将您的代码更改为double(time_taken)/CLOCKS_PER_SEC以获得浮点。