title: What does model.eval() do in pytorch?
body: <p>When should I use <code>.eval()</code>? I understand it is supposed to allow me to &quot;evaluate my model&quot;. How do I turn it back off for training?</p>
  <p>Example training <a href="https://github.com/natanielruiz/deep-head-pose/blob/master/code/train_hopenet.py" rel="noreferrer">code</a> using <code>.eval()</code>.</p>