def transformer_tall_train_uniencdec():
  """Train CNN/DM with a unidirectional encoder and decoder."""
  hparams = transformer_tall()
  hparams.max_input_seq_length = 750
  hparams.max_target_seq_length = 100
  hparams.optimizer = "true_adam"
  hparams.learning_rate_schedule = ("linear_warmup*constant*cosdecay")
  hparams.learning_rate_decay_steps = 150000
  hparams.learning_rate_constant = 2e-4
  hparams.unidirectional_encoder = True
  return hparams