src/gmxlib/gmx_blas/sdot.c

   1 #include "gmx_blas.h"
   2
   3
   4 float
   5 F77_FUNC(sdot,SDOT)(int *n_arg,
   6                     float *dx,
   7                     int *incx_arg,
   8                     float *dy,
   9                     int *incy_arg)
  10 {
  11     int i,ix,iy,m;
  12     int n=*n_arg;
  13     int incx = *incx_arg;
  14     int incy = *incy_arg;
  15     float t1;
  16
  17     if(n<=0)
  18         return 0.0;
  19
  20     t1 = 0.0;
  21
  22     if(incx!=1 || incy!=1) {
  23         ix = 0;
  24         iy = 0;
  25         if(incx<0)
  26             ix = (1-n)*incx;
  27         if(incy<0)
  28             iy = (1-n)*incy;
  29
  30         for(i=0;i<n;i++,ix+=incx,iy+=incy)
  31             t1 += dx[ix] * dy[iy];
  32
  33         return t1;
  34
  35     } else {
  36
  37         m = n%5;
  38
  39         for(i=0;i<m;i++)
  40             t1 += dx[i] * dy[i];
  41
  42         /* unroll */
  43         for(i=m;i<n;i+=5)
  44             t1  =  t1 + dx[i] * dy[i]
  45                 +    dx[i+1] * dy[i+1]
  46                 +    dx[i+2] * dy[i+2]
  47                 +    dx[i+3] * dy[i+3]
  48                 +    dx[i+4] * dy[i+4];
  49
  50         return t1;
  51     }
  52 }
  53
  54