for ( j=0; j<array_len; j+ =8 )
   {
   total += array[j+0];
   total += array[j+1];
   total += array[j+2]; /* Main body of
   total += array[j+3]; * loop is unrolled
   total += array[j+4]; * for greater speed.
   total += array[j+5]; */
   total += array[j+6];
   total += array[j+7];
   }