TensorFlow, why there are 3 files after saving the model?

Question

Having read the docs, I saved a model in TensorFlow, here is my demo 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)

but after that, I found there are 3 files

model.ckpt.data-00000-of-00001
model.ckpt.index
model.ckpt.meta

And I can't restore the model by restore the model.ckpt file, since there is no such file. Here is my code

with tf.Session() as sess:
  # Restore variables from disk.
  saver.restore(sess, "/tmp/model.ckpt")

So, why there are 3 files?

Answer 1

Try this:

with tf.Session() as sess:
    saver = tf.train.import_meta_graph('/tmp/model.ckpt.meta')
    saver.restore(sess, "/tmp/model.ckpt")

The TensorFlow save method saves three kinds of files because it stores the graph structure separately from the variable values. The .meta file describes the saved graph structure, so you need to import it before restoring the checkpoint (otherwise it doesn't know what variables the saved checkpoint values correspond to).

Alternatively, you could do this:

# Recreate the EXACT SAME variables
v1 = tf.Variable(..., name="v1")
v2 = tf.Variable(..., name="v2")

...

# Now load the checkpoint variable values
with tf.Session() as sess:
    saver = tf.train.Saver()
    saver.restore(sess, "/tmp/model.ckpt")

Even though there is no file named model.ckpt, you still refer to the saved checkpoint by that name when restoring it. From the saver.py source code:

Users only need to interact with the user-specified prefix... instead of any physical pathname.