# -*- coding: utf-8 -*-
"""Recurrent layers and their base classes.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import numpy as np
import warnings
from .. import backend as K
from .. import activations
from .. import initializers
from .. import regularizers
from .. import constraints
from ..engine.base_layer import Layer
from ..engine.base_layer import InputSpec
from ..utils.generic_utils import has_arg
from ..utils.generic_utils import to_list
# Legacy support.
from ..legacy.layers import Recurrent
from ..legacy import interfaces
class StackedRNNCells(Layer):
"""Wrapper allowing a stack of RNN cells to behave as a single cell.
Used to implement efficient stacked RNNs.
# Arguments
cells: List of RNN cell instances.
# Examples
```python
cells = [
keras.layers.LSTMCell(output_dim),
keras.layers.LSTMCell(output_dim),
keras.layers.LSTMCell(output_dim),
]
inputs = keras.Input((timesteps, input_dim))
x = keras.layers.RNN(cells)(inputs)
```
"""
def __init__(self, cells, **kwargs):
for cell in cells:
if not hasattr(cell, 'call'):
raise ValueError('All cells must have a `call` method. '
'received cells:', cells)
if not hasattr(cell, 'state_size'):
raise ValueError('All cells must have a '
'`state_size` attribute. '
'received cells:', cells)
self.cells = cells
# reverse_state_order determines whether the state size will be in a
# reverse order of the cells' state. User might want to set this to True
# to keep the existing behavior. This is only useful when use
# `RNN(return_state=True)` since the state will be returned as the same
# order of state_size.
self.reverse_state_order = kwargs.pop('reverse_state_order', False)
if self.reverse_state_order:
warnings.warn('`reverse_state_order=True` in `StackedRNNCells` '
'will soon be deprecated. Please update the code to '
'work with the natural order of states if you '
'reply on the RNN states, '
'eg `RNN(return_state=True)`.')
super(StackedRNNCells, self).__init__(**kwargs)
@property
def state_size(self):
# States are a flat list of the individual cell state size.
# e.g. states of a 2-layer LSTM would be `[h1, c1, h2, c2]`.
# (assuming one LSTM has states [h, c])
# In the case of reverse_state_order=True, the state_size will be
# `[h2, c2, h1, c1]`.
state_size = []
for cell in self.cells[::-1] if self.reverse_state_order else self.cells:
if hasattr(cell.state_size, '__len__'):
state_size += list(cell.state_size)
else:
state_size.append(cell.state_size)
return tuple(state_size)
@property
def output_size(self):
if getattr(self.cells[-1], 'output_size', None) is not None:
return self.cells[-1].output_size
if hasattr(self.cells[-1].state_size, '__len__'):
return self.cells[-1].state_size[0]
else:
return self.cells[-1].state_size
def call(self, inputs, states, constants=None, **kwargs):
# Recover per-cell states.
nested_states = []
for cell in self.cells[::-1] if self.reverse_state_order else self.cells:
if hasattr(cell.state_size, '__len__'):
nested_states.append(states[:len(cell.state_size)])
states = states[len(cell.state_size):]
else:
nested_states.append([states[0]])
states = states[1:]
if self.reverse_state_order:
nested_states = nested_states[::-1]
# Call the cells in order and store the returned states.
new_nested_states = []
for cell, states in zip(self.cells, nested_states):
if has_arg(cell.call, 'constants'):
inputs, states = cell.call(inputs, states,
constants=constants,
**kwargs)
else:
inputs, states = cell.call(inputs, states, **kwargs)
new_nested_states.append(states)
# Format the new states as a flat list
# in reverse cell order.
new_states = []
if self.reverse_state_order:
new_nested_states = new_nested_states[::-1]
for cell_states in new_nested_states:
new_states += cell_states
return inputs, new_states
def build(self, input_shape):
if isinstance(input_shape, list):
constants_shape = input_shape[1:]
input_shape = input_shape[0]
for cell in self.cells:
if isinstance(cell, Layer):
if has_arg(cell.call, 'constants'):
cell.build([input_shape] + constants_shape)
else:
cell.build(input_shape)
if getattr(cell, 'output_size', None) is not None:
output_dim = cell.output_size
elif hasattr(cell.state_size, '__len__'):
output_dim = cell.state_size[0]
else:
output_dim = cell.state_size
input_shape = (input_shape[0], output_dim)
self.built = True
def get_config(self):
cells = []
for cell in self.cells:
cells.append({'class_name': cell.__class__.__name__,
'config': cell.get_config()})
config = {'cells': cells}
base_config = super(StackedRNNCells, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
@classmethod
def from_config(cls, config, custom_objects=None):
from . import deserialize as deserialize_layer
cells = []
for cell_config in config.pop('cells'):
cells.append(deserialize_layer(cell_config,
custom_objects=custom_objects))
return cls(cells, **config)
@property
def trainable_weights(self):
if not self.trainable:
return []
weights = []
for cell in self.cells:
if isinstance(cell, Layer):
weights += cell.trainable_weights
return weights
@property
def non_trainable_weights(self):
weights = []
for cell in self.cells:
if isinstance(cell, Layer):
weights += cell.non_trainable_weights
if not self.trainable:
trainable_weights = []
for cell in self.cells:
if isinstance(cell, Layer):
trainable_weights += cell.trainable_weights
return trainable_weights + weights
return weights
def get_weights(self):
"""Retrieves the weights of the model.
# Returns
A flat list of Numpy arrays.
"""
weights = []
for cell in self.cells:
if isinstance(cell, Layer):
weights += cell.weights
return K.batch_get_value(weights)
def set_weights(self, weights):
"""Sets the weights of the model.
# Arguments
weights: A list of Numpy arrays with shapes and types matching
the output of `model.get_weights()`.
"""
tuples = []
for cell in self.cells:
if isinstance(cell, Layer):
num_param = len(cell.weights)
weights = weights[:num_param]
for sw, w in zip(cell.weights, weights):
tuples.append((sw, w))
weights = weights[num_param:]
K.batch_set_value(tuples)
@property
def losses(self):
losses = []
for cell in self.cells:
if isinstance(cell, Layer):
cell_losses = cell.losses
losses += cell_losses
return losses
def get_losses_for(self, inputs=None):
losses = []
for cell in self.cells:
if isinstance(cell, Layer):
cell_losses = cell.get_losses_for(inputs)
losses += cell_losses
return losses
class RNN(Layer):
"""Base class for recurrent layers.
# Arguments
cell: A RNN cell instance. A RNN cell is a class that has:
- a `call(input_at_t, states_at_t)` method, returning
`(output_at_t, states_at_t_plus_1)`. The call method of the
cell can also take the optional argument `constants`, see
section "Note on passing external constants" below.
- a `state_size` attribute. This can be a single integer
(single state) in which case it is
the size of the recurrent state
(which should be the same as the size of the cell output).
This can also be a list/tuple of integers
(one size per state).
- a `output_size` attribute. This can be a single integer or a
TensorShape, which represent the shape of the output. For
backward compatible reason, if this attribute is not available
for the cell, the value will be inferred by the first element
of the `state_size`.
It is also possible for `cell` to be a list of RNN cell instances,
in which cases the cells get stacked on after the other in the RNN,
implementing an efficient stacked RNN.
return_sequences: Boolean. Whether to return the last output
in the output sequence, or the full sequence.
return_state: Boolean. Whether to return the last state
in addition to the output.
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.
input_dim: dimensionality of the input (integer).
This argument (or alternatively,
the keyword argument `input_shape`)
is required when using this layer as the first layer in a model.
input_length: Length of input sequences, to be specified
when it is constant.
This argument is required if you are going to connect
`Flatten` then `Dense` layers upstream
(without it, the shape of the dense outputs cannot be computed).
Note that if the recurrent layer is not the first layer
in your model, you would need to specify the input length
at the level of the first layer
(e.g. via the `input_shape` argument)
# Input shape
3D tensor with shape `(batch_size, timesteps, input_dim)`.
# Output shape
- if `return_state`: a list of tensors. The first tensor is
the output. The remaining tensors are the last states,
each with shape `(batch_size, units)`.
- if `return_sequences`: 3D tensor with shape
`(batch_size, timesteps, units)`.
- else, 2D tensor with shape `(batch_size, units)`.
# Masking
This layer supports masking for input data with a variable number
of timesteps. To introduce masks to your data,
use an [Embedding](embeddings.md) layer with the `mask_zero` parameter
set to `True`.
# Note on using statefulness in RNNs
You can set RNN layers to be 'stateful', which means that the states
computed for the samples in one batch will be reused as initial states
for the samples in the next batch. This assumes a one-to-one mapping
between samples in different successive batches.
To enable statefulness:
- specify `stateful=True` in the layer constructor.
- specify a fixed batch size for your model, by passing
if sequential model:
`batch_input_shape=(...)` to the first layer in your model.
else for functional model with 1 or more Input layers:
`batch_shape=(...)` to all the first layers in your model.
This is the expected shape of your inputs
*including the batch size*.
It should be a tuple of integers, e.g. `(32, 10, 100)`.
- specify `shuffle=False` when calling fit().
To reset the states of your model, call `.reset_states()` on either
a specific layer, or on your entire model.
# Note on specifying the initial state of RNNs
You can specify the initial state of RNN layers symbolically by
calling them with the keyword argument `initial_state`. The value of
`initial_state` should be a tensor or list of tensors representing
the initial state of the RNN layer.
You can specify the initial state of RNN layers numerically by
calling `reset_states` with the keyword argument `states`. The value of
`states` should be a numpy array or list of numpy arrays representing
the initial state of the RNN layer.
# Note on passing external constants to RNNs
You can pass "external" constants to the cell using the `constants`
keyword argument of `RNN.__call__` (as well as `RNN.call`) method. This
requires that the `cell.call` method accepts the same keyword argument
`constants`. Such constants can be used to condition the cell
transformation on additional static inputs (not changing over time),
a.k.a. an attention mechanism.
# Examples
```python
# First, let's define a RNN Cell, as a layer subclass.
class MinimalRNNCell(keras.layers.Layer):
def __init__(self, units, **kwargs):
self.units = units
self.state_size = units
super(MinimalRNNCell, self).__init__(**kwargs)
def build(self, input_shape):
self.kernel = self.add_weight(shape=(input_shape[-1], self.units),
initializer='uniform',
name='kernel')
self.recurrent_kernel = self.add_weight(
shape=(self.units, self.units),
initializer='uniform',
name='recurrent_kernel')
self.built = True
def call(self, inputs, states):
prev_output = states[0]
h = K.dot(inputs, self.kernel)
output = h + K.dot(prev_output, self.recurrent_kernel)
return output, [output]
# Let's use this cell in a RNN layer:
cell = MinimalRNNCell(32)
x = keras.Input((None, 5))
layer = RNN(cell)
y = layer(x)
# Here's how to use the cell to build a stacked RNN:
cells = [MinimalRNNCell(32), MinimalRNNCell(64)]
x = keras.Input((None, 5))
layer = RNN(cells)
y = layer(x)
```
"""
def __init__(self, cell,
return_sequences=False,
return_state=False,
go_backwards=False,
stateful=False,
unroll=False,
**kwargs):
if isinstance(cell, (list, tuple)):
cell = StackedRNNCells(cell)
if not hasattr(cell, 'call'):
raise ValueError('`cell` should have a `call` method. '
'The RNN was passed:', cell)
if not hasattr(cell, 'state_size'):
raise ValueError('The RNN cell should have '
'an attribute `state_size` '
'(tuple of integers, '
'one integer per RNN state).')
super(RNN, self).__init__(**kwargs)
self.cell = cell
self.return_sequences = return_sequences
self.return_state = return_state
self.go_backwards = go_backwards
self.stateful = stateful
self.unroll = unroll
self.supports_masking = True
self.input_spec = [InputSpec(ndim=3)]
self.state_spec = None
self._states = None
self.constants_spec = None
self._num_constants = None
@property
def states(self):
if self._states is None:
if isinstance(self.cell.state_size, int):
num_states = 1
else:
num_states = len(self.cell.state_size)
return [None for _ in range(num_states)]
return self._states
@states.setter
def states(self, states):
self._states = states
def compute_output_shape(self, input_shape):
if isinstance(input_shape, list):
input_shape = input_shape[0]
if hasattr(self.cell.state_size, '__len__'):
state_size = self.cell.state_size
else:
state_size = [self.cell.state_size]
if getattr(self.cell, 'output_size', None) is not None:
output_dim = self.cell.output_size
else:
output_dim = state_size[0]
if self.return_sequences:
output_shape = (input_shape[0], input_shape[1], output_dim)
else:
output_shape = (input_shape[0], output_dim)
if self.return_state:
state_shape = [(input_shape[0], dim) for dim in state_size]
return [output_shape] + state_shape
else:
return output_shape
def compute_mask(self, inputs, mask):
if isinstance(mask, list):
mask = mask[0]
output_mask = mask if self.return_sequences else None
if self.return_state:
state_mask = [None for _ in self.states]
return [output_mask] + state_mask
else:
return output_mask
def build(self, input_shape):
# Note input_shape will be list of shapes of initial states and
# constants if these are passed in __call__.
if self._num_constants is not None:
constants_shape = input_shape[-self._num_constants:]
else:
constants_shape = None
if isinstance(input_shape, list):
input_shape = input_shape[0]
batch_size = input_shape[0] if self.stateful else None
input_dim = input_shape[-1]
self.input_spec[0] = InputSpec(shape=(batch_size, None, input_dim))
# allow cell (if layer) to build before we set or validate state_spec
if isinstance(self.cell, Layer):
step_input_shape = (input_shape[0],) + input_shape[2:]
if constants_shape is not None:
self.cell.build([step_input_shape] + constants_shape)
else:
self.cell.build(step_input_shape)
# set or validate state_spec
if hasattr(self.cell.state_size, '__len__'):
state_size = list(self.cell.state_size)
else:
state_size = [self.cell.state_size]
if self.state_spec is not None:
# initial_state was passed in call, check compatibility
if [spec.shape[-1] for spec in self.state_spec] != state_size:
raise ValueError(
'An `initial_state` was passed that is not compatible with '
'`cell.state_size`. Received `state_spec`={}; '
'however `cell.state_size` is '
'{}'.format(self.state_spec, self.cell.state_size))
else:
self.state_spec = [InputSpec(shape=(None, dim))
for dim in state_size]
if self.stateful:
self.reset_states()
self.built = True
def get_initial_state(self, inputs):
# build an all-zero tensor of shape (samples, output_dim)
initial_state = K.zeros_like(inputs) # (samples, timesteps, input_dim)
initial_state = K.sum(initial_state, axis=(1, 2)) # (samples,)
initial_state = K.expand_dims(initial_state) # (samples, 1)
if hasattr(self.cell.state_size, '__len__'):
return [K.tile(initial_state, [1, dim])
for dim in self.cell.state_size]
else:
return [K.tile(initial_state, [1, self.cell.state_size])]
def __call__(self, inputs, initial_state=None, constants=None, **kwargs):
inputs, initial_state, constants = _standardize_args(
inputs, initial_state, constants, self._num_constants)
if initial_state is None and constants is None:
return super(RNN, self).__call__(inputs, **kwargs)
# If any of `initial_state` or `constants` are specified and are Keras
# tensors, then add them to the inputs and temporarily modify the
# input_spec to include them.
additional_inputs = []
additional_specs = []
if initial_state is not None:
kwargs['initial_state'] = initial_state
additional_inputs += initial_state
self.state_spec = [InputSpec(shape=K.int_shape(state))
for state in initial_state]
additional_specs += self.state_spec
if constants is not None:
kwargs['constants'] = constants
additional_inputs += constants
self.constants_spec = [InputSpec(shape=K.int_shape(constant))
for constant in constants]
self._num_constants = len(constants)
additional_specs += self.constants_spec
# at this point additional_inputs cannot be empty
is_keras_tensor = K.is_keras_tensor(additional_inputs[0])
for tensor in additional_inputs:
if K.is_keras_tensor(tensor) != is_keras_tensor:
raise ValueError('The initial state or constants of an RNN'
' layer cannot be specified with a mix of'
' Keras tensors and non-Keras tensors'
' (a "Keras tensor" is a tensor that was'
' returned by a Keras layer, or by `Input`)')
if is_keras_tensor:
# Compute the full input spec, including state and constants
full_input = [inputs] + additional_inputs
full_input_spec = self.input_spec + additional_specs
# Perform the call with temporarily replaced input_spec
original_input_spec = self.input_spec
self.input_spec = full_input_spec
output = super(RNN, self).__call__(full_input, **kwargs)
self.input_spec = original_input_spec
return output
else:
return super(RNN, self).__call__(inputs, **kwargs)
def call(self,
inputs,
mask=None,
training=None,
initial_state=None,
constants=None):
# input shape: `(samples, time (padded with zeros), input_dim)`
# note that the .build() method of subclasses MUST define
# self.input_spec and self.state_spec with complete input shapes.
if isinstance(inputs, list):
# get initial_state from full input spec
# as they could be copied to multiple GPU.
if self._num_constants is None:
initial_state = inputs[1:]
else:
initial_state = inputs[1:-self._num_constants]
if len(initial_state) == 0:
initial_state = None
inputs = inputs[0]
if initial_state is not None:
pass
elif self.stateful:
initial_state = self.states
else:
initial_state = self.get_initial_state(inputs)
if isinstance(mask, list):
mask = mask[0]
if len(initial_state) != len(self.states):
raise ValueError('Layer has ' + str(len(self.states)) +
' states but was passed ' +
str(len(initial_state)) +
' initial states.')
input_shape = K.int_shape(inputs)
timesteps = input_shape[1]
if self.unroll and timesteps in [None, 1]:
raise ValueError('Cannot unroll a RNN if the '
'time dimension is undefined or equal to 1. \n'
'- If using a Sequential model, '
'specify the time dimension by passing '
'an `input_shape` or `batch_input_shape` '
'argument to your first layer. If your '
'first layer is an Embedding, you can '
'also use the `input_length` argument.\n'
'- If using the functional API, specify '
'the time dimension by passing a `shape` '
'or `batch_shape` argument to your Input layer.')
kwargs = {}
if has_arg(self.cell.call, 'training'):
kwargs['training'] = training
if constants:
if not has_arg(self.cell.call, 'constants'):
raise ValueError('RNN cell does not support constants')
def step(inputs, states):
constants = states[-self._num_constants:]
states = states[:-self._num_constants]
return self.cell.call(inputs, states, constants=constants,
**kwargs)
else:
def step(inputs, states):
return self.cell.call(inputs, states, **kwargs)
last_output, outputs, states = K.rnn(step,
inputs,
initial_state,
constants=constants,
go_backwards=self.go_backwards,
mask=mask,
unroll=self.unroll,
input_length=timesteps)
if self.stateful:
updates = []
for i in range(len(states)):
updates.append((self.states[i], states[i]))
self.add_update(updates, inputs)
if self.return_sequences:
output = outputs
else:
output = last_output
# Properly set learning phase
if getattr(last_output, '_uses_learning_phase', False):
output._uses_learning_phase = True
for state in states:
state._uses_learning_phase = True
if self.return_state:
states = to_list(states, allow_tuple=True)
return [output] + states
else:
return output
def reset_states(self, states=None):
if not self.stateful:
raise AttributeError('Layer must be stateful.')
batch_size = self.input_spec[0].shape[0]
if not batch_size:
raise ValueError('If a RNN is stateful, it needs to know '
'its batch size. Specify the batch size '
'of your input tensors: \n'
'- If using a Sequential model, '
'specify the batch size by passing '
'a `batch_input_shape` '
'argument to your first layer.\n'
'- If using the functional API, specify '
'the batch size by passing a '
'`batch_shape` argument to your Input layer.')
# initialize state if None
if self.states[0] is None:
if hasattr(self.cell.state_size, '__len__'):
self.states = [K.zeros((batch_size, dim))
for dim in self.cell.state_size]
else:
self.states = [K.zeros((batch_size, self.cell.state_size))]
elif states is None:
if hasattr(self.cell.state_size, '__len__'):
for state, dim in zip(self.states, self.cell.state_size):
K.set_value(state, np.zeros((batch_size, dim)))
else:
K.set_value(self.states[0],
np.zeros((batch_size, self.cell.state_size)))
else:
states = to_list(states, allow_tuple=True)
if len(states) != len(self.states):
raise ValueError('Layer ' + self.name + ' expects ' +
str(len(self.states)) + ' states, '
'but it received ' + str(len(states)) +
' state values. Input received: ' +
str(states))
for index, (value, state) in enumerate(zip(states, self.states)):
if hasattr(self.cell.state_size, '__len__'):
dim = self.cell.state_size[index]
else:
dim = self.cell.state_size
if value.shape != (batch_size, dim):
raise ValueError('State ' + str(index) +
' is incompatible with layer ' +
self.name + ': expected shape=' +
str((batch_size, dim)) +
', found shape=' + str(value.shape))
# TODO: consider batch calls to `set_value`.
K.set_value(state, value)
def get_config(self):
config = {'return_sequences': self.return_sequences,
'return_state': self.return_state,
'go_backwards': self.go_backwards,
'stateful': self.stateful,
'unroll': self.unroll}
if self._num_constants is not None:
config['num_constants'] = self._num_constants
cell_config = self.cell.get_config()
config['cell'] = {'class_name': self.cell.__class__.__name__,
'config': cell_config}
base_config = super(RNN, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
@classmethod
def from_config(cls, config, custom_objects=None):
from . import deserialize as deserialize_layer
cell = deserialize_layer(config.pop('cell'),
custom_objects=custom_objects)
num_constants = config.pop('num_constants', None)
layer = cls(cell, **config)
layer._num_constants = num_constants
return layer
@property
def trainable_weights(self):
if not self.trainable:
return []
if isinstance(self.cell, Layer):
return self.cell.trainable_weights
return []
@property
def non_trainable_weights(self):
if isinstance(self.cell, Layer):
if not self.trainable:
return self.cell.weights
return self.cell.non_trainable_weights
return []
@property
def losses(self):
layer_losses = super(RNN, self).losses
if isinstance(self.cell, Layer):
return self.cell.losses + layer_losses
return layer_losses
def get_losses_for(self, inputs=None):
if isinstance(self.cell, Layer):
cell_losses = self.cell.get_losses_for(inputs)
return cell_losses + super(RNN, self).get_losses_for(inputs)
return super(RNN, self).get_losses_for(inputs)
class SimpleRNNCell(Layer):
"""Cell class for SimpleRNN.
# Arguments
units: Positive integer, dimensionality of the output space.
activation: Activation function to use
(see [activations](../activations.md)).
Default: hyperbolic tangent (`tanh`).
If you pass `None`, no activation is applied
(ie. "linear" activation: `a(x) = x`).
use_bias: Boolean, whether the layer uses a bias vector.
kernel_initializer: Initializer for the `kernel` weights matrix,
used for the linear transformation of the inputs
(see [initializers](../initializers.md)).
recurrent_initializer: Initializer for the `recurrent_kernel`
weights matrix,
used for the linear transformation of the recurrent state
(see [initializers](../initializers.md)).
bias_initializer: Initializer for the bias vector
(see [initializers](../initializers.md)).
kernel_regularizer: Regularizer function applied to
the `kernel` weights matrix
(see [regularizer](../regularizers.md)).
recurrent_regularizer: Regularizer function applied to
the `recurrent_kernel` weights matrix
(see [regularizer](../regularizers.md)).
bias_regularizer: Regularizer function applied to the bias vector
(see [regularizer](../regularizers.md)).
kernel_constraint: Constraint function applied to
the `kernel` weights matrix
(see [constraints](../constraints.md)).
recurrent_constraint: Constraint function applied to
the `recurrent_kernel` weights matrix
(see [constraints](../constraints.md)).
bias_constraint: Constraint function applied to the bias vector
(see [constraints](../constraints.md)).
dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the inputs.
recurrent_dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the recurrent state.
"""
def __init__(self, units,
activation='tanh',
use_bias=True,
kernel_initializer='glorot_uniform',
recurrent_initializer='orthogonal',
bias_initializer='zeros',
kernel_regularizer=None,
recurrent_regularizer=None,
bias_regularizer=None,
kernel_constraint=None,
recurrent_constraint=None,
bias_constraint=None,
dropout=0.,
recurrent_dropout=0.,
**kwargs):
super(SimpleRNNCell, self).__init__(**kwargs)
self.units = units
self.activation = activations.get(activation)
self.use_bias = use_bias
self.kernel_initializer = initializers.get(kernel_initializer)
self.recurrent_initializer = initializers.get(recurrent_initializer)
self.bias_initializer = initializers.get(bias_initializer)
self.kernel_regularizer = regularizers.get(kernel_regularizer)
self.recurrent_regularizer = regularizers.get(recurrent_regularizer)
self.bias_regularizer = regularizers.get(bias_regularizer)
self.kernel_constraint = constraints.get(kernel_constraint)
self.recurrent_constraint = constraints.get(recurrent_constraint)
self.bias_constraint = constraints.get(bias_constraint)
self.dropout = min(1., max(0., dropout))
self.recurrent_dropout = min(1., max(0., recurrent_dropout))
self.state_size = self.units
self.output_size = self.units
self._dropout_mask = None
self._recurrent_dropout_mask = None
def build(self, input_shape):
self.kernel = self.add_weight(shape=(input_shape[-1], self.units),
name='kernel',
initializer=self.kernel_initializer,
regularizer=self.kernel_regularizer,
constraint=self.kernel_constraint)
self.recurrent_kernel = self.add_weight(
shape=(self.units, self.units),
name='recurrent_kernel',
initializer=self.recurrent_initializer,
regularizer=self.recurrent_regularizer,
constraint=self.recurrent_constraint)
if self.use_bias:
self.bias = self.add_weight(shape=(self.units,),
name='bias',
initializer=self.bias_initializer,
regularizer=self.bias_regularizer,
constraint=self.bias_constraint)
else:
self.bias = None
self.built = True
def call(self, inputs, states, training=None):
prev_output = states[0]
if 0 < self.dropout < 1 and self._dropout_mask is None:
self._dropout_mask = _generate_dropout_mask(
K.ones_like(inputs),
self.dropout,
training=training)
if (0 < self.recurrent_dropout < 1 and
self._recurrent_dropout_mask is None):
self._recurrent_dropout_mask = _generate_dropout_mask(
K.ones_like(prev_output),
self.recurrent_dropout,
training=training)
dp_mask = self._dropout_mask
rec_dp_mask = self._recurrent_dropout_mask
if dp_mask is not None:
h = K.dot(inputs * dp_mask, self.kernel)
else:
h = K.dot(inputs, self.kernel)
if self.bias is not None:
h = K.bias_add(h, self.bias)
if rec_dp_mask is not None:
prev_output *= rec_dp_mask
output = h + K.dot(prev_output, self.recurrent_kernel)
if self.activation is not None:
output = self.activation(output)
# Properly set learning phase on output tensor.
if 0 < self.dropout + self.recurrent_dropout:
if training is None:
output._uses_learning_phase = True
return output, [output]
def get_config(self):
config = {'units': self.units,
'activation': activations.serialize(self.activation),
'use_bias': self.use_bias,
'kernel_initializer':
initializers.serialize(self.kernel_initializer),
'recurrent_initializer':
initializers.serialize(self.recurrent_initializer),
'bias_initializer': initializers.serialize(self.bias_initializer),
'kernel_regularizer':
regularizers.serialize(self.kernel_regularizer),
'recurrent_regularizer':
regularizers.serialize(self.recurrent_regularizer),
'bias_regularizer': regularizers.serialize(self.bias_regularizer),
'kernel_constraint': constraints.serialize(self.kernel_constraint),
'recurrent_constraint':
constraints.serialize(self.recurrent_constraint),
'bias_constraint': constraints.serialize(self.bias_constraint),
'dropout': self.dropout,
'recurrent_dropout': self.recurrent_dropout}
base_config = super(SimpleRNNCell, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
class SimpleRNN(RNN):
"""Fully-connected RNN where the output is to be fed back to input.
# Arguments
units: Positive integer, dimensionality of the output space.
activation: Activation function to use
(see [activations](../activations.md)).
Default: hyperbolic tangent (`tanh`).
If you pass `None`, no activation is applied
(ie. "linear" activation: `a(x) = x`).
use_bias: Boolean, whether the layer uses a bias vector.
kernel_initializer: Initializer for the `kernel` weights matrix,
used for the linear transformation of the inputs
(see [initializers](../initializers.md)).
recurrent_initializer: Initializer for the `recurrent_kernel`
weights matrix,
used for the linear transformation of the recurrent state
(see [initializers](../initializers.md)).
bias_initializer: Initializer for the bias vector
(see [initializers](../initializers.md)).
kernel_regularizer: Regularizer function applied to
the `kernel` weights matrix
(see [regularizer](../regularizers.md)).
recurrent_regularizer: Regularizer function applied to
the `recurrent_kernel` weights matrix
(see [regularizer](../regularizers.md)).
bias_regularizer: Regularizer function applied to the bias vector
(see [regularizer](../regularizers.md)).
activity_regularizer: Regularizer function applied to
the output of the layer (its "activation").
(see [regularizer](../regularizers.md)).
kernel_constraint: Constraint function applied to
the `kernel` weights matrix
(see [constraints](../constraints.md)).
recurrent_constraint: Constraint function applied to
the `recurrent_kernel` weights matrix
(see [constraints](../constraints.md)).
bias_constraint: Constraint function applied to the bias vector
(see [constraints](../constraints.md)).
dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the inputs.
recurrent_dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the recurrent state.
return_sequences: Boolean. Whether to return the last output
in the output sequence, or the full sequence.
return_state: Boolean. Whether to return the last state
in addition to the output.
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.
"""
@interfaces.legacy_recurrent_support
def __init__(self, units,
activation='tanh',
use_bias=True,
kernel_initializer='glorot_uniform',
recurrent_initializer='orthogonal',
bias_initializer='zeros',
kernel_regularizer=None,
recurrent_regularizer=None,
bias_regularizer=None,
activity_regularizer=None,
kernel_constraint=None,
recurrent_constraint=None,
bias_constraint=None,
dropout=0.,
recurrent_dropout=0.,
return_sequences=False,
return_state=False,
go_backwards=False,
stateful=False,
unroll=False,
**kwargs):
if 'implementation' in kwargs:
kwargs.pop('implementation')
warnings.warn('The `implementation` argument '
'in `SimpleRNN` has been deprecated. '
'Please remove it from your layer call.')
if K.backend() == 'theano' and (dropout or recurrent_dropout):
warnings.warn(
'RNN dropout is no longer supported with the Theano backend '
'due to technical limitations. '
'You can either set `dropout` and `recurrent_dropout` to 0, '
'or use the TensorFlow backend.')
dropout = 0.
recurrent_dropout = 0.
cell = SimpleRNNCell(units,
activation=activation,
use_bias=use_bias,
kernel_initializer=kernel_initializer,
recurrent_initializer=recurrent_initializer,
bias_initializer=bias_initializer,
kernel_regularizer=kernel_regularizer,
recurrent_regularizer=recurrent_regularizer,
bias_regularizer=bias_regularizer,
kernel_constraint=kernel_constraint,
recurrent_constraint=recurrent_constraint,
bias_constraint=bias_constraint,
dropout=dropout,
recurrent_dropout=recurrent_dropout)
super(SimpleRNN, self).__init__(cell,
return_sequences=return_sequences,
return_state=return_state,
go_backwards=go_backwards,
stateful=stateful,
unroll=unroll,
**kwargs)
self.activity_regularizer = regularizers.get(activity_regularizer)
def call(self, inputs, mask=None, training=None, initial_state=None):
self.cell._dropout_mask = None
self.cell._recurrent_dropout_mask = None
return super(SimpleRNN, self).call(inputs,
mask=mask,
training=training,
initial_state=initial_state)
@property
def units(self):
return self.cell.units
@property
def activation(self):
return self.cell.activation
@property
def use_bias(self):
return self.cell.use_bias
@property
def kernel_initializer(self):
return self.cell.kernel_initializer
@property
def recurrent_initializer(self):
return self.cell.recurrent_initializer
@property
def bias_initializer(self):
return self.cell.bias_initializer
@property
def kernel_regularizer(self):
return self.cell.kernel_regularizer
@property
def recurrent_regularizer(self):
return self.cell.recurrent_regularizer
@property
def bias_regularizer(self):
return self.cell.bias_regularizer
@property
def kernel_constraint(self):
return self.cell.kernel_constraint
@property
def recurrent_constraint(self):
return self.cell.recurrent_constraint
@property
def bias_constraint(self):
return self.cell.bias_constraint
@property
def dropout(self):
return self.cell.dropout
@property
def recurrent_dropout(self):
return self.cell.recurrent_dropout
def get_config(self):
config = {'units': self.units,
'activation': activations.serialize(self.activation),
'use_bias': self.use_bias,
'kernel_initializer':
initializers.serialize(self.kernel_initializer),
'recurrent_initializer':
initializers.serialize(self.recurrent_initializer),
'bias_initializer': initializers.serialize(self.bias_initializer),
'kernel_regularizer':
regularizers.serialize(self.kernel_regularizer),
'recurrent_regularizer':
regularizers.serialize(self.recurrent_regularizer),
'bias_regularizer': regularizers.serialize(self.bias_regularizer),
'activity_regularizer':
regularizers.serialize(self.activity_regularizer),
'kernel_constraint': constraints.serialize(self.kernel_constraint),
'recurrent_constraint':
constraints.serialize(self.recurrent_constraint),
'bias_constraint': constraints.serialize(self.bias_constraint),
'dropout': self.dropout,
'recurrent_dropout': self.recurrent_dropout}
base_config = super(SimpleRNN, self).get_config()
del base_config['cell']
return dict(list(base_config.items()) + list(config.items()))
@classmethod
def from_config(cls, config):
if 'implementation' in config:
config.pop('implementation')
return cls(**config)
class GRUCell(Layer):
"""Cell class for the GRU layer.
# Arguments
units: Positive integer, dimensionality of the output space.
activation: Activation function to use
(see [activations](../activations.md)).
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
(see [activations](../activations.md)).
Default: hard sigmoid (`hard_sigmoid`).
If you pass `None`, no activation is applied
(ie. "linear" activation: `a(x) = x`).
use_bias: Boolean, whether the layer uses a bias vector.
kernel_initializer: Initializer for the `kernel` weights matrix,
used for the linear transformation of the inputs
(see [initializers](../initializers.md)).
recurrent_initializer: Initializer for the `recurrent_kernel`
weights matrix,
used for the linear transformation of the recurrent state
(see [initializers](../initializers.md)).
bias_initializer: Initializer for the bias vector
(see [initializers](../initializers.md)).
kernel_regularizer: Regularizer function applied to
the `kernel` weights matrix
(see [regularizer](../regularizers.md)).
recurrent_regularizer: Regularizer function applied to
the `recurrent_kernel` weights matrix
(see [regularizer](../regularizers.md)).
bias_regularizer: Regularizer function applied to the bias vector
(see [regularizer](../regularizers.md)).
kernel_constraint: Constraint function applied to
the `kernel` weights matrix
(see [constraints](../constraints.md)).
recurrent_constraint: Constraint function applied to
the `recurrent_kernel` weights matrix
(see [constraints](../constraints.md)).
bias_constraint: Constraint function applied to the bias vector
(see [constraints](../constraints.md)).
dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the inputs.
recurrent_dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the recurrent state.
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 will
batch them into fewer, larger operations. These modes will
have different performance profiles on different hardware and
for different applications.
reset_after: GRU convention (whether to apply reset gate after or
before matrix multiplication). False = "before" (default),
True = "after" (CuDNN compatible).
"""
def __init__(self, units,
activation='tanh',
recurrent_activation='hard_sigmoid',
use_bias=True,
kernel_initializer='glorot_uniform',
recurrent_initializer='orthogonal',
bias_initializer='zeros',
kernel_regularizer=None,
recurrent_regularizer=None,
bias_regularizer=None,
kernel_constraint=None,
recurrent_constraint=None,
bias_constraint=None,
dropout=0.,
recurrent_dropout=0.,
implementation=1,
reset_after=False,
**kwargs):
super(GRUCell, self).__init__(**kwargs)
self.units = units
self.activation = activations.get(activation)
self.recurrent_activation = activations.get(recurrent_activation)
self.use_bias = use_bias
self.kernel_initializer = initializers.get(kernel_initializer)
self.recurrent_initializer = initializers.get(recurrent_initializer)
self.bias_initializer = initializers.get(bias_initializer)
self.kernel_regularizer = regularizers.get(kernel_regularizer)
self.recurrent_regularizer = regularizers.get(recurrent_regularizer)
self.bias_regularizer = regularizers.get(bias_regularizer)
self.kernel_constraint = constraints.get(kernel_constraint)
self.recurrent_constraint = constraints.get(recurrent_constraint)
self.bias_constraint = constraints.get(bias_constraint)
self.dropout = min(1., max(0., dropout))
self.recurrent_dropout = min(1., max(0., recurrent_dropout))
self.implementation = implementation
self.reset_after = reset_after
self.state_size = self.units
self.output_size = self.units
self._dropout_mask = None
self._recurrent_dropout_mask = None
def build(self, input_shape):
input_dim = input_shape[-1]
self.kernel = self.add_weight(shape=(input_dim, self.units * 3),
name='kernel',
initializer=self.kernel_initializer,
regularizer=self.kernel_regularizer,
constraint=self.kernel_constraint)
self.recurrent_kernel = self.add_weight(
shape=(self.units, self.units * 3),
name='recurrent_kernel',
initializer=self.recurrent_initializer,
regularizer=self.recurrent_regularizer,
constraint=self.recurrent_constraint)
if self.use_bias:
if not self.reset_after:
bias_shape = (3 * self.units,)
else:
# separate biases for input and recurrent kernels
# Note: the shape is intentionally different from CuDNNGRU biases
# `(2 * 3 * self.units,)`, so that we can distinguish the classes
# when loading and converting saved weights.
bias_shape = (2, 3 * self.units)
self.bias = self.add_weight(shape=bias_shape,
name='bias',
initializer=self.bias_initializer,
regularizer=self.bias_regularizer,
constraint=self.bias_constraint)
if not self.reset_after:
self.input_bias, self.recurrent_bias = self.bias, None
else:
# NOTE: need to flatten, since slicing in CNTK gives 2D array
self.input_bias = K.flatten(self.bias[0])
self.recurrent_bias = K.flatten(self.bias[1])
else:
self.bias = None
# update gate
self.kernel_z = self.kernel[:, :self.units]
self.recurrent_kernel_z = self.recurrent_kernel[:, :self.units]
# reset gate
self.kernel_r = self.kernel[:, self.units: self.units * 2]
self.recurrent_kernel_r = self.recurrent_kernel[:,
self.units:
self.units * 2]
# new gate
self.kernel_h = self.kernel[:, self.units * 2:]
self.recurrent_kernel_h = self.recurrent_kernel[:, self.units * 2:]
if self.use_bias:
# bias for inputs
self.input_bias_z = self.input_bias[:self.units]
self.input_bias_r = self.input_bias[self.units: self.units * 2]
self.input_bias_h = self.input_bias[self.units * 2:]
# bias for hidden state - just for compatibility with CuDNN
if self.reset_after:
self.recurrent_bias_z = self.recurrent_bias[:self.units]
self.recurrent_bias_r = (
self.recurrent_bias[self.units: self.units * 2])
self.recurrent_bias_h = self.recurrent_bias[self.units * 2:]
else:
self.input_bias_z = None
self.input_bias_r = None
self.input_bias_h = None
if self.reset_after:
self.recurrent_bias_z = None
self.recurrent_bias_r = None
self.recurrent_bias_h = None
self.built = True
def call(self, inputs, states, training=None):
h_tm1 = states[0] # previous memory
if 0 < self.dropout < 1 and self._dropout_mask is None:
self._dropout_mask = _generate_dropout_mask(
K.ones_like(inputs),
self.dropout,
training=training,
count=3)
if (0 < self.recurrent_dropout < 1 and
self._recurrent_dropout_mask is None):
self._recurrent_dropout_mask = _generate_dropout_mask(
K.ones_like(h_tm1),
self.recurrent_dropout,
training=training,
count=3)
# dropout matrices for input units
dp_mask = self._dropout_mask
# dropout matrices for recurrent units
rec_dp_mask = self._recurrent_dropout_mask
if self.implementation == 1:
if 0. < self.dropout < 1.:
inputs_z = inputs * dp_mask[0]
inputs_r = inputs * dp_mask[1]
inputs_h = inputs * dp_mask[2]
else:
inputs_z = inputs
inputs_r = inputs
inputs_h = inputs
x_z = K.dot(inputs_z, self.kernel_z)
x_r = K.dot(inputs_r, self.kernel_r)
x_h = K.dot(inputs_h, self.kernel_h)
if self.use_bias:
x_z = K.bias_add(x_z, self.input_bias_z)
x_r = K.bias_add(x_r, self.input_bias_r)
x_h = K.bias_add(x_h, self.input_bias_h)
if 0. < self.recurrent_dropout < 1.:
h_tm1_z = h_tm1 * rec_dp_mask[0]
h_tm1_r = h_tm1 * rec_dp_mask[1]
h_tm1_h = h_tm1 * rec_dp_mask[2]
else:
h_tm1_z = h_tm1
h_tm1_r = h_tm1
h_tm1_h = h_tm1
recurrent_z = K.dot(h_tm1_z, self.recurrent_kernel_z)
recurrent_r = K.dot(h_tm1_r, self.recurrent_kernel_r)
if self.reset_after and self.use_bias:
recurrent_z = K.bias_add(recurrent_z, self.recurrent_bias_z)
recurrent_r = K.bias_add(recurrent_r, self.recurrent_bias_r)
z = self.recurrent_activation(x_z + recurrent_z)
r = self.recurrent_activation(x_r + recurrent_r)
# reset gate applied after/before matrix multiplication
if self.reset_after:
recurrent_h = K.dot(h_tm1_h, self.recurrent_kernel_h)
if self.use_bias:
recurrent_h = K.bias_add(recurrent_h, self.recurrent_bias_h)
recurrent_h = r * recurrent_h
else:
recurrent_h = K.dot(r * h_tm1_h, self.recurrent_kernel_h)
hh = self.activation(x_h + recurrent_h)
else:
if 0. < self.dropout < 1.:
inputs *= dp_mask[0]
# inputs projected by all gate matrices at once
matrix_x = K.dot(inputs, self.kernel)
if self.use_bias:
# biases: bias_z_i, bias_r_i, bias_h_i
matrix_x = K.bias_add(matrix_x, self.input_bias)
x_z = matrix_x[:, :self.units]
x_r = matrix_x[:, self.units: 2 * self.units]
x_h = matrix_x[:, 2 * self.units:]
if 0. < self.recurrent_dropout < 1.:
h_tm1 *= rec_dp_mask[0]
if self.reset_after:
# hidden state projected by all gate matrices at once
matrix_inner = K.dot(h_tm1, self.recurrent_kernel)
if self.use_bias:
matrix_inner = K.bias_add(matrix_inner, self.recurrent_bias)
else:
# hidden state projected separately for update/reset and new
matrix_inner = K.dot(h_tm1,
self.recurrent_kernel[:, :2 * self.units])
recurrent_z = matrix_inner[:, :self.units]
recurrent_r = matrix_inner[:, self.units: 2 * self.units]
z = self.recurrent_activation(x_z + recurrent_z)
r = self.recurrent_activation(x_r + recurrent_r)
if self.reset_after:
recurrent_h = r * matrix_inner[:, 2 * self.units:]
else:
recurrent_h = K.dot(r * h_tm1,
self.recurrent_kernel[:, 2 * self.units:])
hh = self.activation(x_h + recurrent_h)
# previous and candidate state mixed by update gate
h = z * h_tm1 + (1 - z) * hh
if 0 < self.dropout + self.recurrent_dropout:
if training is None:
h._uses_learning_phase = True
return h, [h]
def get_config(self):
config = {'units': self.units,
'activation': activations.serialize(self.activation),
'recurrent_activation':
activations.serialize(self.recurrent_activation),
'use_bias': self.use_bias,
'kernel_initializer':
initializers.serialize(self.kernel_initializer),
'recurrent_initializer':
initializers.serialize(self.recurrent_initializer),
'bias_initializer': initializers.serialize(self.bias_initializer),
'kernel_regularizer':
regularizers.serialize(self.kernel_regularizer),
'recurrent_regularizer':
regularizers.serialize(self.recurrent_regularizer),
'bias_regularizer': regularizers.serialize(self.bias_regularizer),
'kernel_constraint': constraints.serialize(self.kernel_constraint),
'recurrent_constraint':
constraints.serialize(self.recurrent_constraint),
'bias_constraint': constraints.serialize(self.bias_constraint),
'dropout': self.dropout,
'recurrent_dropout': self.recurrent_dropout,
'implementation': self.implementation,
'reset_after': self.reset_after}
base_config = super(GRUCell, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
class GRU(RNN):
"""Gated Recurrent Unit - Cho et al. 2014.
There are two variants. The default one is based on 1406.1078v3 and
has reset gate applied to hidden state before matrix multiplication. The
other one is based on original 1406.1078v1 and has the order reversed.
The second variant is compatible with CuDNNGRU (GPU-only) and allows
inference on CPU. Thus it has separate biases for `kernel` and
`recurrent_kernel`. Use `'reset_after'=True` and
`recurrent_activation='sigmoid'`.
# Arguments
units: Positive integer, dimensionality of the output space.
activation: Activation function to use
(see [activations](../activations.md)).
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
(see [activations](../activations.md)).
Default: hard sigmoid (`hard_sigmoid`).
If you pass `None`, no activation is applied
(ie. "linear" activation: `a(x) = x`).
use_bias: Boolean, whether the layer uses a bias vector.
kernel_initializer: Initializer for the `kernel` weights matrix,
used for the linear transformation of the inputs
(see [initializers](../initializers.md)).
recurrent_initializer: Initializer for the `recurrent_kernel`
weights matrix,
used for the linear transformation of the recurrent state
(see [initializers](../initializers.md)).
bias_initializer: Initializer for the bias vector
(see [initializers](../initializers.md)).
kernel_regularizer: Regularizer function applied to
the `kernel` weights matrix
(see [regularizer](../regularizers.md)).
recurrent_regularizer: Regularizer function applied to
the `recurrent_kernel` weights matrix
(see [regularizer](../regularizers.md)).
bias_regularizer: Regularizer function applied to the bias vector
(see [regularizer](../regularizers.md)).
activity_regularizer: Regularizer function applied to
the output of the layer (its "activation").
(see [regularizer](../regularizers.md)).
kernel_constraint: Constraint function applied to
the `kernel` weights matrix
(see [constraints](../constraints.md)).
recurrent_constraint: Constraint function applied to
the `recurrent_kernel` weights matrix
(see [constraints](../constraints.md)).
bias_constraint: Constraint function applied to the bias vector
(see [constraints](../constraints.md)).
dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the inputs.
recurrent_dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the recurrent state.
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 will
batch them into fewer, larger operations. These modes will
have different performance profiles on different hardware and
for different applications.
return_sequences: Boolean. Whether to return the last output
in the output sequence, or the full sequence.
return_state: Boolean. Whether to return the last state
in addition to the output.
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.
reset_after: GRU convention (whether to apply reset gate after or
before matrix multiplication). False = "before" (default),
True = "after" (CuDNN compatible).
# References
- [Learning Phrase Representations using RNN Encoder-Decoder for
Statistical Machine Translation](https://arxiv.org/abs/1406.1078)
- [On the Properties of Neural Machine Translation:
Encoder-Decoder Approaches](https://arxiv.org/abs/1409.1259)
- [Empirical Evaluation of Gated Recurrent Neural Networks on
Sequence Modeling](https://arxiv.org/abs/1412.3555v1)
- [A Theoretically Grounded Application of Dropout in
Recurrent Neural Networks](https://arxiv.org/abs/1512.05287)
"""
@interfaces.legacy_recurrent_support
def __init__(self, units,
activation='tanh',
recurrent_activation='hard_sigmoid',
use_bias=True,
kernel_initializer='glorot_uniform',
recurrent_initializer='orthogonal',
bias_initializer='zeros',
kernel_regularizer=None,
recurrent_regularizer=None,
bias_regularizer=None,
activity_regularizer=None,
kernel_constraint=None,
recurrent_constraint=None,
bias_constraint=None,
dropout=0.,
recurrent_dropout=0.,
implementation=1,
return_sequences=False,
return_state=False,
go_backwards=False,
stateful=False,
unroll=False,
reset_after=False,
**kwargs):
if implementation == 0:
warnings.warn('`implementation=0` has been deprecated, '
'and now defaults to `implementation=1`.'
'Please update your layer call.')
if K.backend() == 'theano' and (dropout or recurrent_dropout):
warnings.warn(
'RNN dropout is no longer supported with the Theano backend '
'due to technical limitations. '
'You can either set `dropout` and `recurrent_dropout` to 0, '
'or use the TensorFlow backend.')
dropout = 0.
recurrent_dropout = 0.
cell = GRUCell(units,
activation=activation,
recurrent_activation=recurrent_activation,
use_bias=use_bias,
kernel_initializer=kernel_initializer,
recurrent_initializer=recurrent_initializer,
bias_initializer=bias_initializer,
kernel_regularizer=kernel_regularizer,
recurrent_regularizer=recurrent_regularizer,
bias_regularizer=bias_regularizer,
kernel_constraint=kernel_constraint,
recurrent_constraint=recurrent_constraint,
bias_constraint=bias_constraint,
dropout=dropout,
recurrent_dropout=recurrent_dropout,
implementation=implementation,
reset_after=reset_after)
super(GRU, self).__init__(cell,
return_sequences=return_sequences,
return_state=return_state,
go_backwards=go_backwards,
stateful=stateful,
unroll=unroll,
**kwargs)
self.activity_regularizer = regularizers.get(activity_regularizer)
def call(self, inputs, mask=None, training=None, initial_state=None):
self.cell._dropout_mask = None
self.cell._recurrent_dropout_mask = None
return super(GRU, self).call(inputs,
mask=mask,
training=training,
initial_state=initial_state)
@property
def units(self):
return self.cell.units
@property
def activation(self):
return self.cell.activation
@property
def recurrent_activation(self):
return self.cell.recurrent_activation
@property
def use_bias(self):
return self.cell.use_bias
@property
def kernel_initializer(self):
return self.cell.kernel_initializer
@property
def recurrent_initializer(self):
return self.cell.recurrent_initializer
@property
def bias_initializer(self):
return self.cell.bias_initializer
@property
def kernel_regularizer(self):
return self.cell.kernel_regularizer
@property
def recurrent_regularizer(self):
return self.cell.recurrent_regularizer
@property
def bias_regularizer(self):
return self.cell.bias_regularizer
@property
def kernel_constraint(self):
return self.cell.kernel_constraint
@property
def recurrent_constraint(self):
return self.cell.recurrent_constraint
@property
def bias_constraint(self):
return self.cell.bias_constraint
@property
def dropout(self):
return self.cell.dropout
@property
def recurrent_dropout(self):
return self.cell.recurrent_dropout
@property
def implementation(self):
return self.cell.implementation
@property
def reset_after(self):
return self.cell.reset_after
def get_config(self):
config = {'units': self.units,
'activation': activations.serialize(self.activation),
'recurrent_activation':
activations.serialize(self.recurrent_activation),
'use_bias': self.use_bias,
'kernel_initializer':
initializers.serialize(self.kernel_initializer),
'recurrent_initializer':
initializers.serialize(self.recurrent_initializer),
'bias_initializer': initializers.serialize(self.bias_initializer),
'kernel_regularizer':
regularizers.serialize(self.kernel_regularizer),
'recurrent_regularizer':
regularizers.serialize(self.recurrent_regularizer),
'bias_regularizer': regularizers.serialize(self.bias_regularizer),
'activity_regularizer':
regularizers.serialize(self.activity_regularizer),
'kernel_constraint': constraints.serialize(self.kernel_constraint),
'recurrent_constraint':
constraints.serialize(self.recurrent_constraint),
'bias_constraint': constraints.serialize(self.bias_constraint),
'dropout': self.dropout,
'recurrent_dropout': self.recurrent_dropout,
'implementation': self.implementation,
'reset_after': self.reset_after}
base_config = super(GRU, self).get_config()
del base_config['cell']
return dict(list(base_config.items()) + list(config.items()))
@classmethod
def from_config(cls, config):
if 'implementation' in config and config['implementation'] == 0:
config['implementation'] = 1
return cls(**config)
class LSTMCell(Layer):
"""Cell class for the LSTM layer.
# Arguments
units: Positive integer, dimensionality of the output space.
activation: Activation function to use
(see [activations](../activations.md)).
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
(see [activations](../activations.md)).
Default: hard sigmoid (`hard_sigmoid`).
If you pass `None`, no activation is applied
(ie. "linear" activation: `a(x) = x`).x
use_bias: Boolean, whether the layer uses a bias vector.
kernel_initializer: Initializer for the `kernel` weights matrix,
used for the linear transformation of the inputs
(see [initializers](../initializers.md)).
recurrent_initializer: Initializer for the `recurrent_kernel`
weights matrix,
used for the linear transformation of the recurrent state
(see [initializers](../initializers.md)).
bias_initializer: Initializer for the bias vector
(see [initializers](../initializers.md)).
unit_forget_bias: Boolean.
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.]
(http://www.jmlr.org/proceedings/papers/v37/jozefowicz15.pdf).
kernel_regularizer: Regularizer function applied to
the `kernel` weights matrix
(see [regularizer](../regularizers.md)).
recurrent_regularizer: Regularizer function applied to
the `recurrent_kernel` weights matrix
(see [regularizer](../regularizers.md)).
bias_regularizer: Regularizer function applied to the bias vector
(see [regularizer](../regularizers.md)).
kernel_constraint: Constraint function applied to
the `kernel` weights matrix
(see [constraints](../constraints.md)).
recurrent_constraint: Constraint function applied to
the `recurrent_kernel` weights matrix
(see [constraints](../constraints.md)).
bias_constraint: Constraint function applied to the bias vector
(see [constraints](../constraints.md)).
dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the inputs.
recurrent_dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the recurrent state.
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 will
batch them into fewer, larger operations. These modes will
have different performance profiles on different hardware and
for different applications.
"""
def __init__(self, units,
activation='tanh',
recurrent_activation='hard_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,
kernel_constraint=None,
recurrent_constraint=None,
bias_constraint=None,
dropout=0.,
recurrent_dropout=0.,
implementation=1,
**kwargs):
super(LSTMCell, self).__init__(**kwargs)
self.units = units
self.activation = activations.get(activation)
self.recurrent_activation = activations.get(recurrent_activation)
self.use_bias = use_bias
self.kernel_initializer = initializers.get(kernel_initializer)
self.recurrent_initializer = initializers.get(recurrent_initializer)
self.bias_initializer = initializers.get(bias_initializer)
self.unit_forget_bias = unit_forget_bias
self.kernel_regularizer = regularizers.get(kernel_regularizer)
self.recurrent_regularizer = regularizers.get(recurrent_regularizer)
self.bias_regularizer = regularizers.get(bias_regularizer)
self.kernel_constraint = constraints.get(kernel_constraint)
self.recurrent_constraint = constraints.get(recurrent_constraint)
self.bias_constraint = constraints.get(bias_constraint)
self.dropout = min(1., max(0., dropout))
self.recurrent_dropout = min(1., max(0., recurrent_dropout))
self.implementation = implementation
self.state_size = (self.units, self.units)
self.output_size = self.units
self._dropout_mask = None
self._recurrent_dropout_mask = None
def build(self, input_shape):
input_dim = input_shape[-1]
self.kernel = self.add_weight(shape=(input_dim, self.units * 4),
name='kernel',
initializer=self.kernel_initializer,
regularizer=self.kernel_regularizer,
constraint=self.kernel_constraint)
self.recurrent_kernel = self.add_weight(
shape=(self.units, self.units * 4),
name='recurrent_kernel',
initializer=self.recurrent_initializer,
regularizer=self.recurrent_regularizer,
constraint=self.recurrent_constraint)
if self.use_bias:
if self.unit_forget_bias:
def bias_initializer(_, *args, **kwargs):
return K.concatenate([
self.bias_initializer((self.units,), *args, **kwargs),
initializers.Ones()((self.units,), *args, **kwargs),
self.bias_initializer((self.units * 2,), *args, **kwargs),
])
else:
bias_initializer = self.bias_initializer
self.bias = self.add_weight(shape=(self.units * 4,),
name='bias',
initializer=bias_initializer,
regularizer=self.bias_regularizer,
constraint=self.bias_constraint)
else:
self.bias = None
self.kernel_i = self.kernel[:, :self.units]
self.kernel_f = self.kernel[:, self.units: self.units * 2]
self.kernel_c = self.kernel[:, self.units * 2: self.units * 3]
self.kernel_o = self.kernel[:, self.units * 3:]
self.recurrent_kernel_i = self.recurrent_kernel[:, :self.units]
self.recurrent_kernel_f = (
self.recurrent_kernel[:, self.units: self.units * 2])
self.recurrent_kernel_c = (
self.recurrent_kernel[:, self.units * 2: self.units * 3])
self.recurrent_kernel_o = self.recurrent_kernel[:, self.units * 3:]
if self.use_bias:
self.bias_i = self.bias[:self.units]
self.bias_f = self.bias[self.units: self.units * 2]
self.bias_c = self.bias[self.units * 2: self.units * 3]
self.bias_o = self.bias[self.units * 3:]
else:
self.bias_i = None
self.bias_f = None
self.bias_c = None
self.bias_o = None
self.built = True
def call(self, inputs, states, training=None):
if 0 < self.dropout < 1 and self._dropout_mask is None:
self._dropout_mask = _generate_dropout_mask(
K.ones_like(inputs),
self.dropout,
training=training,
count=4)
if (0 < self.recurrent_dropout < 1 and
self._recurrent_dropout_mask is None):
self._recurrent_dropout_mask = _generate_dropout_mask(
K.ones_like(states[0]),
self.recurrent_dropout,
training=training,
count=4)
# dropout matrices for input units
dp_mask = self._dropout_mask
# dropout matrices for recurrent units
rec_dp_mask = self._recurrent_dropout_mask
h_tm1 = states[0] # previous memory state
c_tm1 = states[1] # previous carry state
if self.implementation == 1:
if 0 < self.dropout < 1.:
inputs_i = inputs * dp_mask[0]
inputs_f = inputs * dp_mask[1]
inputs_c = inputs * dp_mask[2]
inputs_o = inputs * dp_mask[3]
else:
inputs_i = inputs
inputs_f = inputs
inputs_c = inputs
inputs_o = inputs
x_i = K.dot(inputs_i, self.kernel_i)
x_f = K.dot(inputs_f, self.kernel_f)
x_c = K.dot(inputs_c, self.kernel_c)
x_o = K.dot(inputs_o, self.kernel_o)
if self.use_bias:
x_i = K.bias_add(x_i, self.bias_i)
x_f = K.bias_add(x_f, self.bias_f)
x_c = K.bias_add(x_c, self.bias_c)
x_o = K.bias_add(x_o, self.bias_o)
if 0 < self.recurrent_dropout < 1.:
h_tm1_i = h_tm1 * rec_dp_mask[0]
h_tm1_f = h_tm1 * rec_dp_mask[1]
h_tm1_c = h_tm1 * rec_dp_mask[2]
h_tm1_o = h_tm1 * rec_dp_mask[3]
else:
h_tm1_i = h_tm1
h_tm1_f = h_tm1
h_tm1_c = h_tm1
h_tm1_o = h_tm1
i = self.recurrent_activation(x_i + K.dot(h_tm1_i,
self.recurrent_kernel_i))
f = self.recurrent_activation(x_f + K.dot(h_tm1_f,
self.recurrent_kernel_f))
c = f * c_tm1 + i * self.activation(x_c + K.dot(h_tm1_c,
self.recurrent_kernel_c))
o = self.recurrent_activation(x_o + K.dot(h_tm1_o,
self.recurrent_kernel_o))
else:
if 0. < self.dropout < 1.:
inputs *= dp_mask[0]
z = K.dot(inputs, self.kernel)
if 0. < self.recurrent_dropout < 1.:
h_tm1 *= rec_dp_mask[0]
z += K.dot(h_tm1, self.recurrent_kernel)
if self.use_bias:
z = K.bias_add(z, self.bias)
z0 = z[:, :self.units]
z1 = z[:, self.units: 2 * self.units]
z2 = z[:, 2 * self.units: 3 * self.units]
z3 = z[:, 3 * self.units:]
i = self.recurrent_activation(z0)
f = self.recurrent_activation(z1)
c = f * c_tm1 + i * self.activation(z2)
o = self.recurrent_activation(z3)
h = o * self.activation(c)
if 0 < self.dropout + self.recurrent_dropout:
if training is None:
h._uses_learning_phase = True
return h, [h, c]
def get_config(self):
config = {'units': self.units,
'activation': activations.serialize(self.activation),
'recurrent_activation':
activations.serialize(self.recurrent_activation),
'use_bias': self.use_bias,
'kernel_initializer':
initializers.serialize(self.kernel_initializer),
'recurrent_initializer':
initializers.serialize(self.recurrent_initializer),
'bias_initializer': initializers.serialize(self.bias_initializer),
'unit_forget_bias': self.unit_forget_bias,
'kernel_regularizer':
regularizers.serialize(self.kernel_regularizer),
'recurrent_regularizer':
regularizers.serialize(self.recurrent_regularizer),
'bias_regularizer': regularizers.serialize(self.bias_regularizer),
'kernel_constraint': constraints.serialize(self.kernel_constraint),
'recurrent_constraint':
constraints.serialize(self.recurrent_constraint),
'bias_constraint': constraints.serialize(self.bias_constraint),
'dropout': self.dropout,
'recurrent_dropout': self.recurrent_dropout,
'implementation': self.implementation}
base_config = super(LSTMCell, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
class LSTM(RNN):
"""Long Short-Term Memory layer - Hochreiter 1997.
# Arguments
units: Positive integer, dimensionality of the output space.
activation: Activation function to use
(see [activations](../activations.md)).
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
(see [activations](../activations.md)).
Default: hard sigmoid (`hard_sigmoid`).
If you pass `None`, no activation is applied
(ie. "linear" activation: `a(x) = x`).
use_bias: Boolean, whether the layer uses a bias vector.
kernel_initializer: Initializer for the `kernel` weights matrix,
used for the linear transformation of the inputs.
(see [initializers](../initializers.md)).
recurrent_initializer: Initializer for the `recurrent_kernel`
weights matrix,
used for the linear transformation of the recurrent state.
(see [initializers](../initializers.md)).
bias_initializer: Initializer for the bias vector
(see [initializers](../initializers.md)).
unit_forget_bias: Boolean.
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.]
(http://www.jmlr.org/proceedings/papers/v37/jozefowicz15.pdf).
kernel_regularizer: Regularizer function applied to
the `kernel` weights matrix
(see [regularizer](../regularizers.md)).
recurrent_regularizer: Regularizer function applied to
the `recurrent_kernel` weights matrix
(see [regularizer](../regularizers.md)).
bias_regularizer: Regularizer function applied to the bias vector
(see [regularizer](../regularizers.md)).
activity_regularizer: Regularizer function applied to
the output of the layer (its "activation").
(see [regularizer](../regularizers.md)).
kernel_constraint: Constraint function applied to
the `kernel` weights matrix
(see [constraints](../constraints.md)).
recurrent_constraint: Constraint function applied to
the `recurrent_kernel` weights matrix
(see [constraints](../constraints.md)).
bias_constraint: Constraint function applied to the bias vector
(see [constraints](../constraints.md)).
dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the inputs.
recurrent_dropout: Float between 0 and 1.
Fraction of the units to drop for
the linear transformation of the recurrent state.
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 will
batch them into fewer, larger operations. These modes will
have different performance profiles on different hardware and
for different applications.
return_sequences: Boolean. Whether to return the last output
in the output sequence, or the full sequence.
return_state: Boolean. Whether to return the last state
in addition to the output.
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.
# References
- [Long short-term memory]
(http://www.bioinf.jku.at/publications/older/2604.pdf)
- [Learning to forget: Continual prediction with LSTM]
(http://www.mitpressjournals.org/doi/pdf/10.1162/089976600300015015)
- [Supervised sequence labeling with recurrent neural networks]
(http://www.cs.toronto.edu/~graves/preprint.pdf)
- [A Theoretically Grounded Application of Dropout in
Recurrent Neural Networks](https://arxiv.org/abs/1512.05287)
"""
@interfaces.legacy_recurrent_support
def __init__(self, units,
activation='tanh',
recurrent_activation='hard_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.,
recurrent_dropout=0.,
implementation=1,
return_sequences=False,
return_state=False,
go_backwards=False,
stateful=False,
unroll=False,
**kwargs):
if implementation == 0:
warnings.warn('`implementation=0` has been deprecated, '
'and now defaults to `implementation=1`.'
'Please update your layer call.')
if K.backend() == 'theano' and (dropout or recurrent_dropout):
warnings.warn(
'RNN dropout is no longer supported with the Theano backend '
'due to technical limitations. '
'You can either set `dropout` and `recurrent_dropout` to 0, '
'or use the TensorFlow backend.')
dropout = 0.
recurrent_dropout = 0.
cell = LSTMCell(units,
activation=activation,
recurrent_activation=recurrent_activation,
use_bias=use_bias,
kernel_initializer=kernel_initializer,
recurrent_initializer=recurrent_initializer,
unit_forget_bias=unit_forget_bias,
bias_initializer=bias_initializer,
kernel_regularizer=kernel_regularizer,
recurrent_regularizer=recurrent_regularizer,
bias_regularizer=bias_regularizer,
kernel_constraint=kernel_constraint,
recurrent_constraint=recurrent_constraint,
bias_constraint=bias_constraint,
dropout=dropout,
recurrent_dropout=recurrent_dropout,
implementation=implementation)
super(LSTM, self).__init__(cell,
return_sequences=return_sequences,
return_state=return_state,
go_backwards=go_backwards,
stateful=stateful,
unroll=unroll,
**kwargs)
self.activity_regularizer = regularizers.get(activity_regularizer)
def call(self, inputs, mask=None, training=None, initial_state=None):
self.cell._dropout_mask = None
self.cell._recurrent_dropout_mask = None
return super(LSTM, self).call(inputs,
mask=mask,
training=training,
initial_state=initial_state)
@property
def units(self):
return self.cell.units
@property
def activation(self):
return self.cell.activation
@property
def recurrent_activation(self):
return self.cell.recurrent_activation
@property
def use_bias(self):
return self.cell.use_bias
@property
def kernel_initializer(self):
return self.cell.kernel_initializer
@property
def recurrent_initializer(self):
return self.cell.recurrent_initializer
@property
def bias_initializer(self):
return self.cell.bias_initializer
@property
def unit_forget_bias(self):
return self.cell.unit_forget_bias
@property
def kernel_regularizer(self):
return self.cell.kernel_regularizer
@property
def recurrent_regularizer(self):
return self.cell.recurrent_regularizer
@property
def bias_regularizer(self):
return self.cell.bias_regularizer
@property
def kernel_constraint(self):
return self.cell.kernel_constraint
@property
def recurrent_constraint(self):
return self.cell.recurrent_constraint
@property
def bias_constraint(self):
return self.cell.bias_constraint
@property
def dropout(self):
return self.cell.dropout
@property
def recurrent_dropout(self):
return self.cell.recurrent_dropout
@property
def implementation(self):
return self.cell.implementation
def get_config(self):
config = {'units': self.units,
'activation': activations.serialize(self.activation),
'recurrent_activation':
activations.serialize(self.recurrent_activation),
'use_bias': self.use_bias,
'kernel_initializer':
initializers.serialize(self.kernel_initializer),
'recurrent_initializer':
initializers.serialize(self.recurrent_initializer),
'bias_initializer': initializers.serialize(self.bias_initializer),
'unit_forget_bias': self.unit_forget_bias,
'kernel_regularizer':
regularizers.serialize(self.kernel_regularizer),
'recurrent_regularizer':
regularizers.serialize(self.recurrent_regularizer),
'bias_regularizer': regularizers.serialize(self.bias_regularizer),
'activity_regularizer':
regularizers.serialize(self.activity_regularizer),
'kernel_constraint': constraints.serialize(self.kernel_constraint),
'recurrent_constraint':
constraints.serialize(self.recurrent_constraint),
'bias_constraint': constraints.serialize(self.bias_constraint),
'dropout': self.dropout,
'recurrent_dropout': self.recurrent_dropout,
'implementation': self.implementation}
base_config = super(LSTM, self).get_config()
del base_config['cell']
return dict(list(base_config.items()) + list(config.items()))
@classmethod
def from_config(cls, config):
if 'implementation' in config and config['implementation'] == 0:
config['implementation'] = 1
return cls(**config)
def _generate_dropout_mask(ones, rate, training=None, count=1):
def dropped_inputs():
return K.dropout(ones, rate)
if count > 1:
return [K.in_train_phase(
dropped_inputs,
ones,
training=training) for _ in range(count)]
return K.in_train_phase(
dropped_inputs,
ones,
training=training)
def _standardize_args(inputs, initial_state, constants, num_constants):
"""Standardize `__call__` to a single list of tensor inputs.
When running a model loaded from file, the input tensors
`initial_state` and `constants` can be passed to `RNN.__call__` as part
of `inputs` instead of by the dedicated keyword arguments. This method
makes sure the arguments are separated and that `initial_state` and
`constants` are lists of tensors (or None).
# Arguments
inputs: tensor or list/tuple of tensors
initial_state: tensor or list of tensors or None
constants: tensor or list of tensors or None
# Returns
inputs: tensor
initial_state: list of tensors or None
constants: list of tensors or None
"""
if isinstance(inputs, list):
assert initial_state is None and constants is None
if num_constants is not None:
constants = inputs[-num_constants:]
inputs = inputs[:-num_constants]
if len(inputs) > 1:
initial_state = inputs[1:]
inputs = inputs[0]
def to_list_or_none(x):
if x is None or isinstance(x, list):
return x
if isinstance(x, tuple):
return list(x)
return [x]
initial_state = to_list_or_none(initial_state)
constants = to_list_or_none(constants)
return inputs, initial_state, constants