csapp2e 家庭作业 5.17

void inner5 (vec_ptr x,vec_ptr y;data_t *dest)
{
 long int i;
 int length = vec_length(x);
 data_t *xdata = get_vec_start(x);
 data_t *ydata = get_vec_start(y);
 data_t sum0 = (data_t)0;
data_t sum1 = (data_t)0;
data_t sum2 = (data_t)0;
 long int limit = length-2;
 for(i=0;i  {
  sum0 = sum0 +xdata[i]*ydata[i];
  sum1 = sum1 +xdata[i+1]*ydata[i+1];
  sum2 = sum2 +xdata[i+2]*ydata[i+2];
 }
 for(;i  {
 sum0 = sum0 + xdata[i]*ydata[i]; 
 }
 *dest = sum0+sum1+sum2;
}

 

A 存储器加载性能

B 因为IA32寄存器数量有限，导致寄存器溢出