title: What's the triplet loss back propagation gradient formula?
body: <p>I am trying to use caffe to implement triplet loss described in <a href="http://arxiv.org/abs/1503.03832" rel="noreferrer">Schroff, Kalenichenko and Philbin "FaceNet: A Unified Embedding for Face Recognition and Clustering", 2015</a>.</p>
  
  <p>I am new to this so how to calculate the gradient in back propagation?</p>