tf.keras.layers.LSTM

Long Short-Term Memory layer - Hochreiter 1997.

Inherits From: RNN, Layer, Operation

tf.keras.layers.LSTM(
    units,
    activation='tanh',
    recurrent_activation='sigmoid',
    use_bias=True,
    kernel_initializer='glorot_uniform',
    recurrent_initializer='orthogonal',
    bias_initializer='zeros',
    unit_forget_bias=True,
    kernel_regularizer=None,
    recurrent_regularizer=None,
    bias_regularizer=None,
    activity_regularizer=None,
    kernel_constraint=None,
    recurrent_constraint=None,
    bias_constraint=None,
    dropout=0.0,
    recurrent_dropout=0.0,
    seed=None,
    return_sequences=False,
    return_state=False,
    go_backwards=False,
    stateful=False,
    unroll=False,
    use_cudnn='auto',
    **kwargs
)

Used in the notebooks

Used in the guide Used in the tutorials

Based on available runtime hardware and constraints, this layer will choose different implementations (cuDNN-based or backend-native) to maximize the performance. If a GPU is available and all the arguments to the layer meet the requirement of the cuDNN kernel (see below for details), the layer will use a fast cuDNN implementation when using the TensorFlow backend. The requirements to use the cuDNN implementation are:

  1. activation == tanh
  2. recurrent_activation == sigmoid
  3. dropout == 0 and recurrent_dropout == 0
  4. unroll is False
  5. use_bias is True
  6. Inputs, if use masking, are strictly right-padded.
  7. Eager execution is enabled in the outermost context.

For example:

inputs = np.random.random((32, 10, 8))
lstm = keras.layers.LSTM(4)
output = lstm(inputs)
output.shape
(32, 4)
lstm = keras.layers.LSTM(
    4, return_sequences=True, return_state=True)
whole_seq_output, final_memory_state, final_carry_state = lstm(inputs)
whole_seq_output.shape
(32, 10, 4)
final_memory_state.shape
(32, 4)
final_carry_state.shape
(32, 4)

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 should use 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. activity_regularizer Regularizer function applied to the output of the layer (its "activation"). 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. seed Random seed for dropout. return_sequences Boolean. Whether to return the last output in the output sequence, or the full sequence. Default: False. return_state Boolean. Whether to return the last state in addition to the output. Default: False. go_backwards Boolean (default: False). If True, process the input sequence backwards and return the reversed sequence. stateful Boolean (default: False). If True, the last state for each sample at index i in a batch will be used as initial state for the sample of index i in the following batch. unroll Boolean (default False). If True, the network will be unrolled, else a symbolic loop will be used. Unrolling can speed-up a RNN, although it tends to be more memory-intensive. Unrolling is only suitable for short sequences. use_cudnn Whether to use a cuDNN-backed implementation. "auto" will attempt to use cuDNN when feasible, and will fallback to the default implementation if not.

inputs A 3D tensor, with shape (batch, timesteps, feature). mask Binary tensor of shape (samples, timesteps) indicating whether a given timestep should be masked (optional). An individual True entry indicates that the corresponding timestep should be utilized, while a False entry indicates that the corresponding timestep should be ignored. Defaults to None. training Python boolean indicating whether the layer should behave in training mode or in inference mode. This argument is passed to the cell when calling it. This is only relevant if dropout or recurrent_dropout is used (optional). Defaults to None. initial_state List of initial state tensors to be passed to the first call of the cell (optional, None causes creation of zero-filled initial state tensors). Defaults to None.

activation

bias_constraint

bias_initializer

bias_regularizer

dropout

input Retrieves the input tensor(s) of a symbolic operation.

Only returns the tensor(s) corresponding to the first time the operation was called. kernel_constraint

kernel_initializer

kernel_regularizer

output Retrieves the output tensor(s) of a layer.

Only returns the tensor(s) corresponding to the first time the operation was called. recurrent_activation

recurrent_constraint

recurrent_dropout

recurrent_initializer

recurrent_regularizer

unit_forget_bias

units

use_bias

Methods

from_config

View source

@classmethod
from_config(
    config
)

Creates a layer from its config.

This method is the reverse of get_config, capable of instantiating the same layer from the config dictionary. It does not handle layer connectivity (handled by Network), nor weights (handled by set_weights).

Args

config A Python dictionary, typically the output of get_config.

Returns
A layer instance.

get_initial_state

View source

get_initial_state(
    batch_size
)

inner_loop

View source

inner_loop(
    sequences, initial_state, mask, training=False
)

reset_state

View source

reset_state()

reset_states

View source

reset_states()

symbolic_call

View source

symbolic_call(
    *args, **kwargs
)