title: OpenCV SURF comparing descriptors
body: <p>Folowing snippet is from <strong>OpenCV</strong> find_obj.cpp which is demo for using <strong>SURF</strong>,</p>
  
  <pre>
  <code>
  double
  compareSURFDescriptors( const float* d1, const float* d2, double best, int length )
  {
      double total_cost = 0;
      assert( length % 4 == 0 );
      int i;
      for( i = 0; i  best )
              break;
      }
      return total_cost;
  }
  
  </code>
  </pre>
  
  <p>As far as I can tell it checking the euclidian distance, what I do not understand is why is it doing it in groups of 4? Why not calculate the whole thing at once?</p>