SIFT opencv2.3.1/2.4.3 both Giving very strange descriptors..like 7., 29., 39., 11., 2.3.1 Giving very strange descriptors

Question

This is very simple code for SIFT,I am getting is very strange descriptors.Are they correct?

descriptor: [ 0., 7., 29., 39., 11., 0., 0., 0., 32., 30., 39., 52., 16., 0., 1., 12., 38., 14., 10., 20., 28., 93., 45., 37., 93., 3., 6., 11., 23., 107., 24., 80., 0., 2., 47., 53., 0., 1., 9., 8., 104., 85., 35., 41., 1., 10., 32., 19., 130., 73., 0., 0., 8., 76., 31., 42., 61., 40., 10., 5., 83., 130., 28., 31., 3., 0., 0., 0., 0., 2., 12., 17., 60., 4., 0., 0., 0., 31., 76., 83., 130., 38., 10., 6., 15., 10., 16., 89., 19., 21., 16., 23., 130., 94., 7., 3., 1. ]

#include "stdafx.h"
#include <iostream>
#include <cv.h>
#include <highgui.h>
#include <C:\opencv243\include\opencv2\nonfree\features2d.hpp>
using namespace cv;
using namespace std; 
int main(int argc, const char* argv[])
{
string path="matrices.xml";
   FileStorage fs(path, FileStorage::WRITE);
   cv::siftFeatureDetector detector;
   cv::SiftDescriptorExtractor extractor; 
   cv::Mat descriptors_1;
   std::vector<cv::KeyPoint> keypoints;
   const cv::Mat input=cv::imread("image path",0);
   detector.detect(input, keypoints);
   extractor.compute( input, keypoints, descriptors_1 );
   fs <<"descriptor"<<descriptors_1;
   fs.release();
   return 0;
}

Answer 1

For some reason unknown to me, the SIFT descriptor implemented in OpenCV converts the final values to uchar (0 - 255) and has always done so since I remember. It is a waste of space, since the resulting values are stored in a float descriptor, and it also hinders matching.

What I do is compile my own version of SIFT where I just leave out the conversion to bytes (in the link), and I get nice floating point values.