Range of hyperparameters.

def universal_transformer_base_range(rhp):
  """Range of hyperparameters."""
  # After starting from base, set intervals for some parameters.
  rhp.set_discrete("num_rec_steps", [6, 8, 10])
  rhp.set_discrete("hidden_size", [1024, 2048, 4096])
  rhp.set_discrete("filter_size", [2048, 4096, 8192])
  rhp.set_discrete("num_heads", [8, 16, 32])
  rhp.set_discrete("transformer_ffn_type", ["sepconv", "fc"])
  rhp.set_float("learning_rate", 0.3, 3.0, scale=rhp.LOG_SCALE)
  rhp.set_float("weight_decay", 0.0, 2.0)