title: Why does prediction needs batch size in Keras?
body: <p>In Keras, to predict class of a datatest, the <code>predict_classes()</code> is used.</p>
  
  <p>For example:</p>
  
  <pre><code>classes = model.predict_classes(X_test, batch_size=32)
  </code></pre>
  
  <p>My question is, I know the usage of <code>batch_size</code> in training, but why does it need a <code>batch_size</code> for prediction? how does it work?</p>