title: Why is the convolutional filter flipped in convolutional neural networks?
body: <p>I don't understand why there is the need to flip filters when using convolutional neural networks.</p>
  
  <p>According to the lasagne documentation,</p>
  
  <blockquote>
    <p>flip_filters : bool (default: True)</p>
    
    <p>Whether to flip the filters before sliding them over the input,
    performing a convolution (this is the default), or not to flip them
    and perform a correlation. Note that for some other convolutional
    layers in Lasagne, flipping incurs an overhead and is disabled by
    default – check the documentation when using learned weights from
    another layer.</p>
  </blockquote>
  
  <p>What does that mean? I never read about flipping filters when convolving in any neural network book. Would someone clarify, please?</p>