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1.计时实例.c
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1.计时实例.c
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#include<stdio.h>
#include<time.h>
#include<math.h>
clock_t start,end;
/* clock_t 是 clock()函数返回的变量类型*/
double duration;
/* 被测函数运行时间,以秒为单位*/
#define MAXN 101 /* 多项式最大项数,即多项式次数+1*/
#define MAXK 1e5 /* 被测函数最大重复调用次数*/
double f1(int n,double a[],double x);
double f2(int n,double a[],double x);
void run(double(*f)(int n,double *,double ),double a[],int func_n);
int main(){
int i;
double a[MAXN]; /* 存储多项式的系数 */
a[0]=1;
for(i=1;i<MAXN;i++)
a[i]=(double)(1.0/i);
run(f1,a,1);
run(f2,a,2);
return 0;
}
double f1(int n,double a[],double x){
int i;
double p=a[0];
for(i=1;i<n;i++)
p+=(a[i]*pow(x,i));
return p;
}
double f2(int n,double a[],double x){
int i;
double p=a[0];
for(i=n;i>0;i--)
p=a[i-1]+x*p;
return p;
}
void run(double(*f)(int n,double *,double ),double a[],int func_n){
int i;
start = clock();
for(i=0;i<MAXK;i++)
f(MAXN-1,a,1.1);
end = clock();
duration = ((double)(end-start))/CLK_TCK;
printf("ticks%d=%f\n",func_n,(double)(end-start));
printf("duration%d=%6.2e\n",func_n,duration);
}