1 #include <stdio.h>
 2 #include <math.h>
 3 #include <time.h>
 4 
 5 clock_t start,stop;
 6 #define max 1e7
 7 #define num 100

 8 void putin(double *);
 9 void f(double *,int ,double );
10 void ff(double *a,int n,double x);
11 void timetext(void (*point)(double *,int,double),double *,int ,double);

12 void main()
13 {
14     double a[num];
15     putin(a);
16     timetext(f,a,num,1.1);
17     timetext(ff,a,num,1.1);
18 
19 }
20 
21 
22 void putin(double *a)
23 { int i;
24     for(i=0;i<num;i++)
25         *(a+i)=(double)i;
26 }
27 
28 void f(double *a,int n,double x)
29 {   int i;
30     double sum=0;
31     for(i=0;i<n;i++)
32         sum=sum+a[i]*pow(x,i);
33 
34 }
35 
36 void ff(double *a,int n,double x)
37 {   int i;
38     double sum=a[n-1];
39     for(i=n-2;i>=0;i--)
40         sum=sum*x+a[i];
41 }
42 
43 void timetext(void (*point)(double *,int,double),double *a,int n,double x)
44 {
45     int i;
46     double duration;
47     start=clock();
48     for(i=0;i<max;i++)
49         (*point)(a,n,x);
50     stop=clock();
51     duration=((double)(stop-start))/max/CLK_TCK;
52     printf("%f\n",duration);
53     printf("%f\n",(double)(stop-start));
54     printf("\n");
55 }