Set of hyperparameters.

def transformer_base_v1():
  """Set of hyperparameters."""
  hparams = common_hparams.basic_params1()
  hparams.norm_type = "layer"
  hparams.hidden_size = 512
  hparams.batch_size = 4096
  hparams.max_length = 256
  hparams.clip_grad_norm = 0.  # i.e. no gradient clipping
  hparams.optimizer_adam_epsilon = 1e-9
  hparams.learning_rate_schedule = "legacy"
  hparams.learning_rate_decay_scheme = "noam"
  hparams.learning_rate = 0.1
  hparams.learning_rate_warmup_steps = 4000
  hparams.initializer_gain = 1.0
  hparams.num_hidden_layers = 6
  hparams.initializer = "uniform_unit_scaling"
  hparams.weight_decay = 0.0
  hparams.optimizer_adam_beta1 = 0.9
  hparams.optimizer_adam_beta2 = 0.98
  hparams.num_sampled_classes = 0
  hparams.label_smoothing = 0.1
  hparams.shared_embedding_and_softmax_weights = True
  hparams.symbol_modality_num_shards = 16

  # Add new ones like this.
  hparams.add_hparam("filter_size", 2048)
  # Layer-related flags. If zero, these fall back on hparams.num_hidden_layers.
  hparams.add_hparam("num_encoder_layers", 0)
  hparams.add_hparam("num_decoder_layers", 0)
  # Attention-related flags.
  hparams.add_hparam("num_heads", 8)
  hparams.add_hparam("attention_key_channels", 0)
  hparams.add_hparam("attention_value_channels", 0)
  hparams.add_hparam("ffn_layer", "dense_relu_dense")
  hparams.add_hparam("parameter_attention_key_channels", 0)
  hparams.add_hparam("parameter_attention_value_channels", 0)
  # All hyperparameters ending in "dropout" are automatically set to 0.0
  # when not in training mode.
  hparams.add_hparam("attention_dropout", 0.0)
  hparams.add_hparam("attention_dropout_broadcast_dims", "")
  hparams.add_hparam("relu_dropout", 0.0)
  hparams.add_hparam("relu_dropout_broadcast_dims", "")
  hparams.add_hparam("pos", "timing")  # timing, none
  hparams.add_hparam("nbr_decoder_problems", 1)
  hparams.add_hparam("proximity_bias", False)
  hparams.add_hparam("causal_decoder_self_attention", True)
  hparams.add_hparam("use_pad_remover", True)
  hparams.add_hparam("self_attention_type", "dot_product")
  hparams.add_hparam("conv_first_kernel", 3)
  hparams.add_hparam("attention_variables_3d", False)
  hparams.add_hparam("use_target_space_embedding", True)
  # These parameters are only used when ffn_layer=="local_moe_tpu"
  hparams.add_hparam("moe_overhead_train", 1.0)
  hparams.add_hparam("moe_overhead_eval", 2.0)
  hparams.moe_num_experts = 16
  hparams.moe_loss_coef = 1e-3
  # If specified, use this value instead of problem name in metrics.py.
  # This is useful for programs that can automatically compare experiments side
  #   by side based on the same metric names.
  hparams.add_hparam("overload_eval_metric_name", "")
  # For making a transformer encoder unidirectional by using masked
  # attention.
  hparams.add_hparam("unidirectional_encoder", False)
  # For hard attention.
  hparams.add_hparam("hard_attention_k", 0)
  return hparams