p7-1.c

UNIX程序设计教程

#include <stdio.h>
#include <time.h>
#include <math.h>
int main (void)
{
    clock_t start, stop1, stop2;
    double x = 0.12;
    int i,j;
    /* 开始统计CPU时间 */ 
    start = clock();  
    for(i = 0; i < 1000000; i++)
        x = log(x);    
    stop1 = clock();
    for(j = 0; j < 1000000; j++)
        x = log(x);
    stop2 = clock();
    printf ("start=%ld, stop1=%ld，stop2=%ld\n", start, stop1,stop2);
    printf ("total elapsed time: %ld , elapsed second: %lf\n",
            stop2 / CLOCKS_PER_SEC, (double)stop2 / CLOCKS_PER_SEC );
    printf ("j loop elapsed time: %ld , elapsed second: %lf\n",
            (stop2 - stop1)/CLOCKS_PER_SEC, 
            (double)(stop2 - stop1)/CLOCKS_PER_SEC );
    printf ("CLOCKS_PER_SEC = %d \n", CLOCKS_PER_SEC);
   
    return 0;
}