HParams for transformer base model for single GPU.

def transformer_base_single_gpu():
  """HParams for transformer base model for single GPU."""
  hparams = transformer_base()
  hparams.batch_size = 1024
  hparams.learning_rate_schedule = "constant*linear_warmup*rsqrt_decay"
  hparams.learning_rate_constant = 0.1
  hparams.learning_rate_warmup_steps = 16000
  return hparams