Hparams for transformer on LM pretraining (with 64k vocab) on TPU.

def transformer_tall_pretrain_lm_tpu_adafactor():
  """Hparams for transformer on LM pretraining (with 64k vocab) on TPU."""
  hparams = transformer_tall_pretrain_lm()
  update_hparams_for_tpu(hparams)
  hparams.max_length = 1024
  # For multi-problem on TPU we need it in absolute examples.
  hparams.batch_size = 8
  hparams.multiproblem_vocab_size = 2**16
  return hparams