Checkpoints input pipeline state every N steps or seconds.

Inherits From: SessionRunHook

This hook saves the state of the iterators in the Graph so that when training is resumed the input pipeline continues from where it left off. This could potentially avoid overfitting in certain pipelines where the number of training steps per eval are small compared to the dataset size or if the training pipeline is pre-empted.

Differences from CheckpointSaverHook:

  1. Saves only the input pipelines in the "iterators" collection and not the global variables or other saveable objects.
  2. Does not write the GraphDef and MetaGraphDef to the summary.

Example of checkpointing the training pipeline:

est = tf.estimator.Estimator(model_fn)
while True:
  # Note: We do not pass the hook here.
  metrics = est.evaluate(eval_input_fn)
  if should_stop_the_training(metrics):

This hook should be used if the input pipeline state needs to be saved separate from the model checkpoint. Doing so may be useful for a few reasons:

  1. Th