title: DescriptorMatcher OpenCV train()
body: <p>The Documentation of OpenCV mentions the function "train()" within a DescriptorMatcher. </p>
  
  <p>"virtual void cv::cuda::DescriptorMatcher::train    (       )<br>
      pure virtual</p>
  
  <p>Trains a descriptor matcher.</p>
  
  <p>Trains a descriptor matcher (for example, the flann index). In all methods to match, the method train() is run every time before matching."(docs)</p>
  
  <p>That's all is said there. Does someone know hot it works? Especially what the DescriptorMatcher needs to train itself. A short example in some OOP language would be amazing.</p>
  
  <p>Here is the Link to the documentation:</p>
  
  <p><a href="http://docs.opencv.org/master/dd/dc5/classcv_1_1cuda_1_1DescriptorMatcher.html#ab220b434f827962455f430a12c65c074" rel="nofollow">http://docs.opencv.org/master/dd/dc5/classcv_1_1cuda_1_1DescriptorMatcher.html#ab220b434f827962455f430a12c65c074</a></p>
  
  <p>Thanks in advance</p>