csapp2e 家庭作业 5.21

4 void psum3(float a[],float p[],long int n)

5 {

6 long int i;

7 p[0] = a[0];

8 float val1,val2,val3=p[0];

9 for (i=1;i<n-2;i+=3)

10 {

11 val1 = val3 + a[i];

12 val2 = val1 + a[i+1];

13 val3 = val2 + a[i+2];

14 p[i]=val1;

15 p[i+1]=val2;

16 p[i+2] = val3;

17 }

18 for(;i<n;i++)

19 p[i]=p[i-1]+a[i];

20

21 }