title: TensorFlow, why there are 3 files after saving the model?
body: <p>Having read the <a href="https://www.tensorflow.org/how_tos/variables/#saving_and_restoring" rel="noreferrer">docs</a>, I saved a model in <code>TensorFlow</code>, here is my demo code:</p>
  
  <pre class="lang-py prettyprint-override"><code># Create some variables.
  v1 = tf.Variable(..., name="v1")
  v2 = tf.Variable(..., name="v2")
  ...
  # Add an op to initialize the variables.
  init_op = tf.global_variables_initializer()
  
  # Add ops to save and restore all the variables.
  saver = tf.train.Saver()
  
  # Later, launch the model, initialize the variables, do some work, save the
  # variables to disk.
  with tf.Session() as sess:
    sess.run(init_op)
    # Do some work with the model.
    ..
    # Save the variables to disk.
    save_path = saver.save(sess, "/tmp/model.ckpt")
    print("Model saved in file: %s" % save_path)
  </code></pre>
  
  <p>but after that, I found there are 3 files</p>
  
  <pre><code>model.ckpt.data-00000-of-00001
  model.ckpt.index
  model.ckpt.meta
  </code></pre>
  
  <p>And I can't restore the model by restore the <code>model.ckpt</code> file, since there is no such file. Here is my code</p>
  
  <pre class="lang-py prettyprint-override"><code>with tf.Session() as sess:
    # Restore variables from disk.
    saver.restore(sess, "/tmp/model.ckpt")
  </code></pre>
  
  <p>So, why there are 3 files?</p>