Bidirectional wrapper for RNNs

  merge_mode = "concat",
  weights = NULL,
  backward_layer = NULL,



What to compose the new Layer instance with. Typically a Sequential model or a Tensor (e.g., as returned by layer_input()). The return value depends on object. If object is:

  • missing or NULL, the Layer instance is returned.

  • a Sequential model, the model with an additional layer is returned.

  • a Tensor, the output tensor from layer_instance(object) is returned.


A RNN layer instance, such as layer_lstm() or layer_gru(). It could also be a keras$layers$Layer instance that meets the following criteria:

  1. Be a sequence-processing layer (accepts 3D+ inputs).

  2. Have a go_backwards, return_sequences and return_state attribute (with the same semantics as for the RNN class).

  3. Have an input_spec attribute.

  4. Implement serialization via get_config() and from_config(). Note that the recommended way to create new RNN layers is to write a custom RNN cell and use it with layer_rnn(), instead of subclassing keras$layers$Layer directly.

  5. When returns_sequences = TRUE, the output of the masked timestep will be zero regardless of the layer's original zero_output_for_mask value.


Mode by which outputs of the forward and backward RNNs will be combined. One of 'sum', 'mul', 'concat', 'ave', NULL. If NULL, the outputs will not be combined, they will be returned as a list. Default value is 'concat'.


Split and propagated to the initial_weights attribute on the forward and backward layer.


Optional keras.layers.RNN, or keras.layers.Layer instance to be used to handle backwards input processing. If backward_layer is not provided, the layer instance passed as the layer argument will be used to generate the backward layer automatically. Note that the provided backward_layer layer should have properties matching those of the layer argument, in particular it should have the same values for stateful, return_states, return_sequences, etc. In addition, backward_layer and layer should have different go_backwards argument values. A ValueError will be raised if these requirements are not met.


standard layer arguments.

See also