tf.keras.layers.LSTMCell

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Class LSTMCell

Cell class for the LSTM layer.

Inherits From: LSTMCell

Used in the guide:

See the Keras RNN API guide for details about the usage of RNN API.

This class processes one step within the whole time sequence input, whereas tf.keras.layer.LSTM processes the whole sequence.

Arguments:

  • units: Positive integer, dimensionality of the output space.
  • activation: Activation function to use. Default: hyperbolic tangent (tanh). If you pass None, no activation is applied (ie. "linear" activation: a(x) = x).
  • recurrent_activation: Activation function to use for the recurrent step. Default: sigmoid (sigmoid). If you pass None, no activation is applied (ie. "linear" activation: a(x) = x).
  • use_bias: Boolean, (default True), whether the layer uses a bias vector.
  • kernel_initializer: Initializer for the kernel weights matrix, used for the linear transformation of the inputs. Default: glorot_uniform.
  • recurrent_initializer: Initializer for the recurrent_kernel weights matrix, used for the linear transformation of the recurrent state. Default: orthogonal.
  • bias_initializer: Initializer for the bias vector. Default: zeros.
  • unit_forget_bias: Boolean (default True). If True, add 1 to the bias of the forget gate at initialization. Setting it to true will also force bias_initializer="zeros". This is recommended in Jozefowicz et al.
  • kernel_regularizer: Regularizer function applied to the kernel weights matrix. Default: None.
  • recurrent_regularizer: Regularizer function applied to the recurrent_kernel weights matrix. Default: None.
  • bias_regularizer: Regularizer function applied to the bias vector. Default: None.
  • kernel_constraint: Constraint function applied to the kernel weights matrix. Default: None.
  • recurrent_constraint: Constraint function applied to the recurrent_kernel weights matrix. Default: None.
  • bias_constraint: Constraint function applied to the bias vector. Default: None.
  • dropout: Float between 0 and 1. Fraction of the units to drop for the linear transformation of the inputs. Default: 0.
  • recurrent_dropout: Float between 0 and 1. Fraction of the units to drop for the linear transformation of the recurrent state. Default: 0.
  • implementation: Implementation mode, either 1 or 2. Mode 1 will structure its operations as a larger number of smaller dot products and additions, whereas mode 2 (default) will batch them into fewer, larger operations. These modes will have different performance profiles on different hardware and for different applications. Default: 2.

Call arguments:

  • inputs: A 2D tensor, with shape of [batch, feature].
  • states: List of 2 tensors that corresponding to the cell's units. Both of them have shape [batch, units], the first tensor is the memory state from previous time step, the second tesnor is the carry state from previous time step. For timestep 0, the initial state provided by user will be feed to cell.
  • training: Python boolean indicating whether the layer should behave in training mode or in inference mode. Only relevant when dropout or recurrent_dropout is used.

Examples:

inputs = np.random.random([32, 10, 8]).astype(np.float32)
rnn = tf.keras.layers.RNN(tf.keras.layers.LSTMCell(4))

output = rnn(inputs)  # The output has shape `[32, 4]`.

rnn = tf.keras.layers.RNN(
    tf.keras.layers.LSTMCell(4),
    return_sequences=True,
    return_state=True)

# whole_sequence_output has shape `[32, 10, 4]`.
# final_memory_state and final_carry_state both have shape `[32, 4]`.
whole_sequence_output, final_memory_state, final_carry_state = rnn(inputs)

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