TensorFlow 1 version | View source on GitHub |
Long Short-Term Memory layer - Hochreiter 1997.
Inherits From: LSTM
, RNN
, Layer
, Module
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,
return_sequences=False, return_state=False, go_backwards=False, stateful=False,
time_major=False, unroll=False, **kwargs
)
Used in the notebooks
Used in the guide | Used in the tutorials |
---|---|
See the Keras RNN API guide for details about the usage of RNN API.
Based on available runtime hardware and constraints, this layer will choose different implementations (cuDNN-based or pure-TensorFlow) 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.
The requirements to use the cuDNN implementation are:
activation
==tanh
recurrent_activation
==sigmoid
recurrent_dropout
== 0unroll
isFalse
use_bias
isTrue
- Inputs, if use masking, are strictly right-padded.
- Eager execution is enabled in the outermost context.
For example:
inputs = tf.random.normal([32, 10, 8])
lstm = tf.keras.layers.LSTM(4)
output = lstm(inputs)
print(output.shape)
(32, 4)
lstm = tf.keras.layers.LSTM(4, return_sequences=True, return_state=True)
whole_seq_output, final_memory_state, final_carry_state = lstm(inputs)
print(whole_seq_output.shape)
(32, 10, 4)
print(final_memory_state.shape)
(32, 4)
print(final_carry_state.shape)
(32, 4)
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 .
|
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. |
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.
|
time_major
|
The shape format of the inputs and outputs tensors.
If True, the inputs and outputs will be in shape
[timesteps, batch, feature] , whereas in the False case, it will be
[batch, timesteps, feature] . Using time_major = True is a bit more
efficient because it avoids transposes at the beginning and end of the
RNN calculation. However, most TensorFlow data is batch-major, so by
default this function accepts input and emits output in batch-major
form.
|
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.
|
Call arguments:
inputs
: A 3D tensor with shape[batch, timesteps, feature]
.mask
: Binary tensor of shape[batch, timesteps]
indicating whether a given timestep should be masked (optional, defaults toNone
).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 ifdropout
orrecurrent_dropout
is used (optional, defaults toNone
).initial_state
: List of initial state tensors to be passed to the first call of the cell (optional, defaults toNone
which causes creation of zero-filled initial state tensors).
Attributes | |
---|---|
activation
|
|
bias_constraint
|
|
bias_initializer
|
|
bias_regularizer
|
|
dropout
|
|
implementation
|
|
kernel_constraint
|
|
kernel_initializer
|
|
kernel_regularizer
|
|
recurrent_activation
|
|
recurrent_constraint
|
|
recurrent_dropout
|
|
recurrent_initializer
|
|
recurrent_regularizer
|
|
states
|
|
unit_forget_bias
|
|
units
|
|
use_bias
|
Methods
get_dropout_mask_for_cell
get_dropout_mask_for_cell(
inputs, training, count=1
)
Get the dropout mask for RNN cell's input.
It will create mask based on context if there isn't any existing cached mask. If a new mask is generated, it will update the cache in the cell.
Args | |
---|---|
inputs
|
The input tensor whose shape will be used to generate dropout mask. |
training
|
Boolean tensor, whether its in training mode, dropout will be ignored in non-training mode. |
count
|
Int, how many dropout mask will be generated. It is useful for cell that has internal weights fused together. |
Returns | |
---|---|
List of mask tensor, generated or cached mask based on context. |
get_recurrent_dropout_mask_for_cell
get_recurrent_dropout_mask_for_cell(
inputs, training, count=1
)
Get the recurrent dropout mask for RNN cell.
It will create mask based on context if there isn't any existing cached mask. If a new mask is generated, it will update the cache in the cell.
Args | |
---|---|
inputs
|
The input tensor whose shape will be used to generate dropout mask. |
training
|
Boolean tensor, whether its in training mode, dropout will be ignored in non-training mode. |
count
|
Int, how many dropout mask will be generated. It is useful for cell that has internal weights fused together. |
Returns | |
---|---|
List of mask tensor, generated or cached mask based on context. |
reset_dropout_mask
reset_dropout_mask()
Reset the cached dropout masks if any.
This is important for the RNN layer to invoke this in it call()
method so
that the cached mask is cleared before calling the cell.call()
. The mask
should be cached across the timestep within the same batch, but shouldn't
be cached between batches. Otherwise it will introduce unreasonable bias
against certain index of data within the batch.
reset_recurrent_dropout_mask
reset_recurrent_dropout_mask()
Reset the cached recurrent dropout masks if any.
This is important for the RNN layer to invoke this in it call() method so that the cached mask is cleared before calling the cell.call(). The mask should be cached across the timestep within the same batch, but shouldn't be cached between batches. Otherwise it will introduce unreasonable bias against certain index of data within the batch.
reset_states
reset_states(
states=None
)
Reset the recorded states for the stateful RNN layer.
Can only be used when RNN layer is constructed with stateful
= True
.
Args:
states: Numpy arrays that contains the value for the initial state, which
will be feed to cell at the first time step. When the value is None,
zero filled numpy array will be created based on the cell state size.
Raises | |
---|---|
AttributeError
|
When the RNN layer is not stateful. |
ValueError
|
When the batch size of the RNN layer is unknown. |
ValueError
|
When the input numpy array is not compatible with the RNN layer state, either size wise or dtype wise. |