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# coding: utf-8
# pylint: disable=no-member, invalid-name, protected-access, no-self-use
# pylint: disable=too-many-branches, too-many-arguments, no-self-use
# pylint: disable=too-many-lines
"""Definition of various recurrent neural network cells."""
from __future__ import print_function
import warnings
import functools
from .. import symbol, init, ndarray
from ..base import string_types, numeric_types
def _cells_state_shape(cells):
return sum([c.state_shape for c in cells], [])
def _cells_state_info(cells):
return sum([c.state_info for c in cells], [])
def _cells_begin_state(cells, **kwargs):
return sum([c.begin_state(**kwargs) for c in cells], [])
def _cells_unpack_weights(cells, args):
for cell in cells:
args = cell.unpack_weights(args)
return args
def _cells_pack_weights(cells, args):
for cell in cells:
args = cell.pack_weights(args)
return args
def _normalize_sequence(length, inputs, layout, merge, in_layout=None):
assert inputs is not None, \
"unroll(inputs=None) has been deprecated. " \
"Please create input variables outside unroll."
axis = layout.find('T')
in_axis = in_layout.find('T') if in_layout is not None else axis
if isinstance(inputs, symbol.Symbol):
if merge is False:
assert len(inputs.list_outputs()) == 1, \
"unroll doesn't allow grouped symbol as input. Please convert " \
"to list with list(inputs) first or let unroll handle splitting."
inputs = list(symbol.split(inputs, axis=in_axis, num_outputs=length,
squeeze_axis=1))
else:
assert length is None or len(inputs) == length
if merge is True:
inputs = [symbol.expand_dims(i, axis=axis) for i in inputs]
inputs = symbol.Concat(*inputs, dim=axis)
in_axis = axis
if isinstance(inputs, symbol.Symbol) and axis != in_axis:
inputs = symbol.swapaxes(inputs, dim0=axis, dim1=in_axis)
return inputs, axis
[docs]class RNNParams(object):
"""Container for holding variables.
Used by RNN cells for parameter sharing between cells.
Parameters
----------
prefix : str
Names of all variables created by this container will
be prepended with prefix.
"""
def __init__(self, prefix=''):
self._prefix = prefix
self._params = {}
[docs] def get(self, name, **kwargs):
"""Get the variable given a name if one exists or create a new one if missing.
Parameters
----------
name : str
name of the variable
**kwargs :
more arguments that's passed to symbol.Variable
"""
name = self._prefix + name
if name not in self._params:
self._params[name] = symbol.Variable(name, **kwargs)
return self._params[name]
[docs]class BaseRNNCell(object):
"""Abstract base class for RNN cells
Parameters
----------
prefix : str, optional
Prefix for names of layers
(this prefix is also used for names of weights if `params` is None
i.e. if `params` are being created and not reused)
params : RNNParams, default None.
Container for weight sharing between cells.
A new RNNParams container is created if `params` is None.
"""
def __init__(self, prefix='', params=None):
if params is None:
params = RNNParams(prefix)
self._own_params = True
else:
self._own_params = False
self._prefix = prefix
self._params = params
self._modified = False
self.reset()
[docs] def reset(self):
"""Reset before re-using the cell for another graph."""
self._init_counter = -1
self._counter = -1
[docs] def __call__(self, inputs, states):
"""Unroll the RNN for one time step.
Parameters
----------
inputs : sym.Variable
input symbol, 2D, batch * num_units
states : list of sym.Variable
RNN state from previous step or the output of begin_state().
Returns
-------
output : Symbol
Symbol corresponding to the output from the RNN when unrolling
for a single time step.
states : nested list of Symbol
The new state of this RNN after this unrolling.
The type of this symbol is same as the output of begin_state().
This can be used as input state to the next time step
of this RNN.
See Also
--------
begin_state: This function can provide the states for the first time step.
unroll: This function unrolls an RNN for a given number of (>=1) time steps.
"""
raise NotImplementedError()
@property
def params(self):
"""Parameters of this cell"""
self._own_params = False
return self._params
@property
def state_info(self):
"""shape and layout information of states"""
raise NotImplementedError()
@property
def state_shape(self):
"""shape(s) of states"""
return [ele['shape'] for ele in self.state_info]
@property
def _gate_names(self):
"""name(s) of gates"""
return ()
[docs] def begin_state(self, func=symbol.zeros, **kwargs):
"""Initial state for this cell.
Parameters
----------
func : callable, default symbol.zeros
Function for creating initial state. Can be symbol.zeros,
symbol.uniform, symbol.Variable etc.
Use symbol.Variable if you want to directly
feed input as states.
**kwargs :
more keyword arguments passed to func. For example
mean, std, dtype, etc.
Returns
-------
states : nested list of Symbol
Starting states for the first RNN step.
"""
assert not self._modified, \
"After applying modifier cells (e.g. DropoutCell) the base " \
"cell cannot be called directly. Call the modifier cell instead."
states = []
for info in self.state_info:
self._init_counter += 1
if info is None:
state = func(name='%sbegin_state_%d'%(self._prefix, self._init_counter),
**kwargs)
else:
kwargs.update(info)
state = func(name='%sbegin_state_%d'%(self._prefix, self._init_counter),
**kwargs)
states.append(state)
return states
[docs] def unpack_weights(self, args):
"""Unpack fused weight matrices into separate
weight matrices.
For example, say you use a module object `mod` to run a network that has an lstm cell.
In `mod.get_params()[0]`, the lstm parameters are all represented as a single big vector.
`cell.unpack_weights(mod.get_params()[0])` will unpack this vector into a dictionary of
more readable lstm parameters - c, f, i, o gates for i2h (input to hidden) and
h2h (hidden to hidden) weights.
Parameters
----------
args : dict of str -> NDArray
Dictionary containing packed weights.
usually from `Module.get_params()[0]`.
Returns
-------
args : dict of str -> NDArray
Dictionary with unpacked weights associated with
this cell.
See Also
--------
pack_weights: Performs the reverse operation of this function.
"""
args = args.copy()
if not self._gate_names:
return args
h = self._num_hidden
for group_name in ['i2h', 'h2h']:
weight = args.pop('%s%s_weight'%(self._prefix, group_name))
bias = args.pop('%s%s_bias' % (self._prefix, group_name))
for j, gate in enumerate(self._gate_names):
wname = '%s%s%s_weight' % (self._prefix, group_name, gate)
args[wname] = weight[j*h:(j+1)*h].copy()
bname = '%s%s%s_bias' % (self._prefix, group_name, gate)
args[bname] = bias[j*h:(j+1)*h].copy()
return args
[docs] def pack_weights(self, args):
"""Pack separate weight matrices into a single packed
weight.
Parameters
----------
args : dict of str -> NDArray
Dictionary containing unpacked weights.
Returns
-------
args : dict of str -> NDArray
Dictionary with packed weights associated with
this cell.
"""
args = args.copy()
if not self._gate_names:
return args
for group_name in ['i2h', 'h2h']:
weight = []
bias = []
for gate in self._gate_names:
wname = '%s%s%s_weight'%(self._prefix, group_name, gate)
weight.append(args.pop(wname))
bname = '%s%s%s_bias'%(self._prefix, group_name, gate)
bias.append(args.pop(bname))
args['%s%s_weight'%(self._prefix, group_name)] = ndarray.concatenate(weight)
args['%s%s_bias'%(self._prefix, group_name)] = ndarray.concatenate(bias)
return args
[docs] def unroll(self, length, inputs, begin_state=None, layout='NTC', merge_outputs=None):
"""Unroll an RNN cell across time steps.
Parameters
----------
length : int
Number of steps to unroll.
inputs : Symbol, list of Symbol, or None
If `inputs` is a single Symbol (usually the output
of Embedding symbol), it should have shape
(batch_size, length, ...) if layout == 'NTC',
or (length, batch_size, ...) if layout == 'TNC'.
If `inputs` is a list of symbols (usually output of
previous unroll), they should all have shape
(batch_size, ...).
begin_state : nested list of Symbol, default None
Input states created by `begin_state()`
or output state of another cell.
Created from `begin_state()` if None.
layout : str, optional
`layout` of input symbol. Only used if inputs
is a single Symbol.
merge_outputs : bool, optional
If False, return outputs as a list of Symbols.
If True, concatenate output across time steps
and return a single symbol with shape
(batch_size, length, ...) if layout == 'NTC',
or (length, batch_size, ...) if layout == 'TNC'.
If None, output whatever is faster.
Returns
-------
outputs : list of Symbol or Symbol
Symbol (if `merge_outputs` is True) or list of Symbols
(if `merge_outputs` is False) corresponding to the output from
the RNN from this unrolling.
states : nested list of Symbol
The new state of this RNN after this unrolling.
The type of this symbol is same as the output of begin_state().
"""
self.reset()
inputs, _ = _normalize_sequence(length, inputs, layout, False)
if begin_state is None:
begin_state = self.begin_state()
states = begin_state
outputs = []
for i in range(length):
output, states = self(inputs[i], states)
outputs.append(output)
outputs, _ = _normalize_sequence(length, outputs, layout, merge_outputs)
return outputs, states
#pylint: disable=no-self-use
def _get_activation(self, inputs, activation, **kwargs):
"""Get activation function. Convert if is string"""
if isinstance(activation, string_types):
return symbol.Activation(inputs, act_type=activation, **kwargs)
else:
return activation(inputs, **kwargs)
[docs]class RNNCell(BaseRNNCell):
"""Simple recurrent neural network cell.
Parameters
----------
num_hidden : int
Number of units in output symbol.
activation : str or Symbol, default 'tanh'
Type of activation function. Options are 'relu' and 'tanh'.
prefix : str, default 'rnn_'
Prefix for name of layers (and name of weight if params is None).
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
"""
def __init__(self, num_hidden, activation='tanh', prefix='rnn_', params=None):
super(RNNCell, self).__init__(prefix=prefix, params=params)
self._num_hidden = num_hidden
self._activation = activation
self._iW = self.params.get('i2h_weight')
self._iB = self.params.get('i2h_bias')
self._hW = self.params.get('h2h_weight')
self._hB = self.params.get('h2h_bias')
@property
def state_info(self):
return [{'shape': (0, self._num_hidden), '__layout__': 'NC'}]
@property
def _gate_names(self):
return ('',)
def __call__(self, inputs, states):
self._counter += 1
name = '%st%d_'%(self._prefix, self._counter)
i2h = symbol.FullyConnected(data=inputs, weight=self._iW, bias=self._iB,
num_hidden=self._num_hidden,
name='%si2h'%name)
h2h = symbol.FullyConnected(data=states[0], weight=self._hW, bias=self._hB,
num_hidden=self._num_hidden,
name='%sh2h'%name)
output = self._get_activation(i2h + h2h, self._activation,
name='%sout'%name)
return output, [output]
[docs]class LSTMCell(BaseRNNCell):
"""Long-Short Term Memory (LSTM) network cell.
Parameters
----------
num_hidden : int
Number of units in output symbol.
prefix : str, default 'lstm_'
Prefix for name of layers (and name of weight if params is None).
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
forget_bias : bias added to forget gate, default 1.0.
Jozefowicz et al. 2015 recommends setting this to 1.0
"""
def __init__(self, num_hidden, prefix='lstm_', params=None, forget_bias=1.0):
super(LSTMCell, self).__init__(prefix=prefix, params=params)
self._num_hidden = num_hidden
self._iW = self.params.get('i2h_weight')
self._hW = self.params.get('h2h_weight')
# we add the forget_bias to i2h_bias, this adds the bias to the forget gate activation
self._iB = self.params.get('i2h_bias', init=init.LSTMBias(forget_bias=forget_bias))
self._hB = self.params.get('h2h_bias')
@property
def state_info(self):
return [{'shape': (0, self._num_hidden), '__layout__': 'NC'},
{'shape': (0, self._num_hidden), '__layout__': 'NC'}]
@property
def _gate_names(self):
return ['_i', '_f', '_c', '_o']
def __call__(self, inputs, states):
self._counter += 1
name = '%st%d_'%(self._prefix, self._counter)
i2h = symbol.FullyConnected(data=inputs, weight=self._iW, bias=self._iB,
num_hidden=self._num_hidden*4,
name='%si2h'%name)
h2h = symbol.FullyConnected(data=states[0], weight=self._hW, bias=self._hB,
num_hidden=self._num_hidden*4,
name='%sh2h'%name)
gates = i2h + h2h
slice_gates = symbol.SliceChannel(gates, num_outputs=4,
name="%sslice"%name)
in_gate = symbol.Activation(slice_gates[0], act_type="sigmoid",
name='%si'%name)
forget_gate = symbol.Activation(slice_gates[1], act_type="sigmoid",
name='%sf'%name)
in_transform = symbol.Activation(slice_gates[2], act_type="tanh",
name='%sc'%name)
out_gate = symbol.Activation(slice_gates[3], act_type="sigmoid",
name='%so'%name)
next_c = symbol._internal._plus(forget_gate * states[1], in_gate * in_transform,
name='%sstate'%name)
next_h = symbol._internal._mul(out_gate, symbol.Activation(next_c, act_type="tanh"),
name='%sout'%name)
return next_h, [next_h, next_c]
[docs]class GRUCell(BaseRNNCell):
"""Gated Rectified Unit (GRU) network cell.
Note: this is an implementation of the cuDNN version of GRUs
(slight modification compared to Cho et al. 2014).
Parameters
----------
num_hidden : int
Number of units in output symbol.
prefix : str, default 'gru_'
Prefix for name of layers (and name of weight if params is None).
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
"""
def __init__(self, num_hidden, prefix='gru_', params=None):
super(GRUCell, self).__init__(prefix=prefix, params=params)
self._num_hidden = num_hidden
self._iW = self.params.get("i2h_weight")
self._iB = self.params.get("i2h_bias")
self._hW = self.params.get("h2h_weight")
self._hB = self.params.get("h2h_bias")
@property
def state_info(self):
return [{'shape': (0, self._num_hidden),
'__layout__': 'NC'}]
@property
def _gate_names(self):
return ['_r', '_z', '_o']
def __call__(self, inputs, states):
# pylint: disable=too-many-locals
self._counter += 1
seq_idx = self._counter
name = '%st%d_' % (self._prefix, seq_idx)
prev_state_h = states[0]
i2h = symbol.FullyConnected(data=inputs,
weight=self._iW,
bias=self._iB,
num_hidden=self._num_hidden * 3,
name="%s_i2h" % name)
h2h = symbol.FullyConnected(data=prev_state_h,
weight=self._hW,
bias=self._hB,
num_hidden=self._num_hidden * 3,
name="%s_h2h" % name)
i2h_r, i2h_z, i2h = symbol.SliceChannel(i2h, num_outputs=3, name="%s_i2h_slice" % name)
h2h_r, h2h_z, h2h = symbol.SliceChannel(h2h, num_outputs=3, name="%s_h2h_slice" % name)
reset_gate = symbol.Activation(i2h_r + h2h_r, act_type="sigmoid",
name="%s_r_act" % name)
update_gate = symbol.Activation(i2h_z + h2h_z, act_type="sigmoid",
name="%s_z_act" % name)
next_h_tmp = symbol.Activation(i2h + reset_gate * h2h, act_type="tanh",
name="%s_h_act" % name)
next_h = symbol._internal._plus((1. - update_gate) * next_h_tmp, update_gate * prev_state_h,
name='%sout' % name)
return next_h, [next_h]
[docs]class FusedRNNCell(BaseRNNCell):
"""Fusing RNN layers across time step into one kernel.
Improves speed but is less flexible. Currently only
supported if using cuDNN on GPU.
Parameters
----------
num_hidden : int
Number of units in output symbol.
num_layers : int, default 1
Number of layers in the cell.
mode : str, default 'lstm'
Type of RNN. options are 'rnn_relu', 'rnn_tanh', 'lstm', 'gru'.
bidirectional : bool, default False
Whether to use bidirectional unroll. The output dimension size is doubled if bidrectional.
dropout : float, default 0.
Fraction of the input that gets dropped out during training time.
get_next_state : bool, default False
Whether to return the states that can be used as starting states next time.
forget_bias : bias added to forget gate, default 1.0.
Jozefowicz et al. 2015 recommends setting this to 1.0
prefix : str, default '$mode_' such as 'lstm_'
Prefix for names of layers
(this prefix is also used for names of weights if `params` is None
i.e. if `params` are being created and not reused)
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
"""
def __init__(self, num_hidden, num_layers=1, mode='lstm', bidirectional=False,
dropout=0., get_next_state=False, forget_bias=1.0,
prefix=None, params=None):
if prefix is None:
prefix = '%s_'%mode
super(FusedRNNCell, self).__init__(prefix=prefix, params=params)
self._num_hidden = num_hidden
self._num_layers = num_layers
self._mode = mode
self._bidirectional = bidirectional
self._dropout = dropout
self._get_next_state = get_next_state
self._directions = ['l', 'r'] if bidirectional else ['l']
initializer = init.FusedRNN(None, num_hidden, num_layers, mode,
bidirectional, forget_bias)
self._parameter = self.params.get('parameters', init=initializer)
@property
def state_info(self):
b = self._bidirectional + 1
n = (self._mode == 'lstm') + 1
return [{'shape': (b*self._num_layers, 0, self._num_hidden), '__layout__': 'LNC'}
for _ in range(n)]
@property
def _gate_names(self):
return {'rnn_relu': [''],
'rnn_tanh': [''],
'lstm': ['_i', '_f', '_c', '_o'],
'gru': ['_r', '_z', '_o']}[self._mode]
@property
def _num_gates(self):
return len(self._gate_names)
def _slice_weights(self, arr, li, lh):
"""slice fused rnn weights"""
args = {}
gate_names = self._gate_names
directions = self._directions
b = len(directions)
p = 0
for layer in range(self._num_layers):
for direction in directions:
for gate in gate_names:
name = '%s%s%d_i2h%s_weight'%(self._prefix, direction, layer, gate)
if layer > 0:
size = b*lh*lh
args[name] = arr[p:p+size].reshape((lh, b*lh))
else:
size = li*lh
args[name] = arr[p:p+size].reshape((lh, li))
p += size
for gate in gate_names:
name = '%s%s%d_h2h%s_weight'%(self._prefix, direction, layer, gate)
size = lh**2
args[name] = arr[p:p+size].reshape((lh, lh))
p += size
for layer in range(self._num_layers):
for direction in directions:
for gate in gate_names:
name = '%s%s%d_i2h%s_bias'%(self._prefix, direction, layer, gate)
args[name] = arr[p:p+lh]
p += lh
for gate in gate_names:
name = '%s%s%d_h2h%s_bias'%(self._prefix, direction, layer, gate)
args[name] = arr[p:p+lh]
p += lh
assert p == arr.size, "Invalid parameters size for FusedRNNCell"
return args
def unpack_weights(self, args):
args = args.copy()
arr = args.pop(self._parameter.name)
b = len(self._directions)
m = self._num_gates
h = self._num_hidden
num_input = arr.size//b//h//m - (self._num_layers - 1)*(h+b*h+2) - h - 2
nargs = self._slice_weights(arr, num_input, self._num_hidden)
args.update({name: nd.copy() for name, nd in nargs.items()})
return args
def pack_weights(self, args):
args = args.copy()
b = self._bidirectional + 1
m = self._num_gates
c = self._gate_names
h = self._num_hidden
w0 = args['%sl0_i2h%s_weight'%(self._prefix, c[0])]
num_input = w0.shape[1]
total = (num_input+h+2)*h*m*b + (self._num_layers-1)*m*h*(h+b*h+2)*b
arr = ndarray.zeros((total,), ctx=w0.context, dtype=w0.dtype)
for name, nd in self._slice_weights(arr, num_input, h).items():
nd[:] = args.pop(name)
args[self._parameter.name] = arr
return args
def __call__(self, inputs, states):
raise NotImplementedError("FusedRNNCell cannot be stepped. Please use unroll")
def unroll(self, length, inputs, begin_state=None, layout='NTC', merge_outputs=None):
self.reset()
inputs, axis = _normalize_sequence(length, inputs, layout, True)
if axis == 1:
warnings.warn("NTC layout detected. Consider using "
"TNC for FusedRNNCell for faster speed")
inputs = symbol.swapaxes(inputs, dim1=0, dim2=1)
else:
assert axis == 0, "Unsupported layout %s"%layout
if begin_state is None:
begin_state = self.begin_state()
states = begin_state
if self._mode == 'lstm':
states = {'state': states[0], 'state_cell': states[1]} # pylint: disable=redefined-variable-type
else:
states = {'state': states[0]}
rnn = symbol.RNN(data=inputs, parameters=self._parameter,
state_size=self._num_hidden, num_layers=self._num_layers,
bidirectional=self._bidirectional, p=self._dropout,
state_outputs=self._get_next_state,
mode=self._mode, name=self._prefix+'rnn',
**states)
attr = {'__layout__' : 'LNC'}
if not self._get_next_state:
outputs, states = rnn, []
elif self._mode == 'lstm':
rnn[1]._set_attr(**attr)
rnn[2]._set_attr(**attr)
outputs, states = rnn[0], [rnn[1], rnn[2]]
else:
rnn[1]._set_attr(**attr)
outputs, states = rnn[0], [rnn[1]]
if axis == 1:
outputs = symbol.swapaxes(outputs, dim1=0, dim2=1)
outputs, _ = _normalize_sequence(length, outputs, layout, merge_outputs)
return outputs, states
[docs] def unfuse(self):
"""Unfuse the fused RNN in to a stack of rnn cells.
Returns
-------
cell : SequentialRNNCell
unfused cell that can be used for stepping, and can run on CPU.
"""
stack = SequentialRNNCell()
get_cell = {'rnn_relu': lambda cell_prefix: RNNCell(self._num_hidden,
activation='relu',
prefix=cell_prefix),
'rnn_tanh': lambda cell_prefix: RNNCell(self._num_hidden,
activation='tanh',
prefix=cell_prefix),
'lstm': lambda cell_prefix: LSTMCell(self._num_hidden,
prefix=cell_prefix),
'gru': lambda cell_prefix: GRUCell(self._num_hidden,
prefix=cell_prefix)}[self._mode]
for i in range(self._num_layers):
if self._bidirectional:
stack.add(BidirectionalCell(
get_cell('%sl%d_'%(self._prefix, i)),
get_cell('%sr%d_'%(self._prefix, i)),
output_prefix='%sbi_l%d_'%(self._prefix, i)))
else:
stack.add(get_cell('%sl%d_'%(self._prefix, i)))
if self._dropout > 0 and i != self._num_layers - 1:
stack.add(DropoutCell(self._dropout, prefix='%s_dropout%d_'%(self._prefix, i)))
return stack
[docs]class SequentialRNNCell(BaseRNNCell):
"""Sequantially stacking multiple RNN cells.
Parameters
----------
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
"""
def __init__(self, params=None):
super(SequentialRNNCell, self).__init__(prefix='', params=params)
self._override_cell_params = params is not None
self._cells = []
[docs] def add(self, cell):
"""Append a cell into the stack.
Parameters
----------
cell : BaseRNNCell
The cell to be appended. During unroll, previous cell's output (or raw inputs if
no previous cell) is used as the input to this cell.
"""
self._cells.append(cell)
if self._override_cell_params:
assert cell._own_params, \
"Either specify params for SequentialRNNCell " \
"or child cells, not both."
cell.params._params.update(self.params._params)
self.params._params.update(cell.params._params)
@property
def state_info(self):
return _cells_state_info(self._cells)
def begin_state(self, **kwargs): # pylint: disable=arguments-differ
assert not self._modified, \
"After applying modifier cells (e.g. ZoneoutCell) the base " \
"cell cannot be called directly. Call the modifier cell instead."
return _cells_begin_state(self._cells, **kwargs)
def unpack_weights(self, args):
return _cells_unpack_weights(self._cells, args)
def pack_weights(self, args):
return _cells_pack_weights(self._cells, args)
def __call__(self, inputs, states):
self._counter += 1
next_states = []
p = 0
for cell in self._cells:
assert not isinstance(cell, BidirectionalCell)
n = len(cell.state_info)
state = states[p:p+n]
p += n
inputs, state = cell(inputs, state)
next_states.append(state)
return inputs, sum(next_states, [])
def unroll(self, length, inputs, begin_state=None, layout='NTC', merge_outputs=None):
self.reset()
num_cells = len(self._cells)
if begin_state is None:
begin_state = self.begin_state()
p = 0
next_states = []
for i, cell in enumerate(self._cells):
n = len(cell.state_info)
states = begin_state[p:p+n]
p += n
inputs, states = cell.unroll(length, inputs=inputs, begin_state=states, layout=layout,
merge_outputs=None if i < num_cells-1 else merge_outputs)
next_states.extend(states)
return inputs, next_states
[docs]class DropoutCell(BaseRNNCell):
"""Apply dropout on input.
Parameters
----------
dropout : float
Percentage of elements to drop out, which
is 1 - percentage to retain.
prefix : str, default 'dropout_'
Prefix for names of layers
(this prefix is also used for names of weights if `params` is None
i.e. if `params` are being created and not reused)
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
"""
def __init__(self, dropout, prefix='dropout_', params=None):
super(DropoutCell, self).__init__(prefix, params)
assert isinstance(dropout, numeric_types), "dropout probability must be a number"
self.dropout = dropout
@property
def state_info(self):
return []
def __call__(self, inputs, states):
if self.dropout > 0:
inputs = symbol.Dropout(data=inputs, p=self.dropout)
return inputs, states
def unroll(self, length, inputs, begin_state=None, layout='NTC', merge_outputs=None):
self.reset()
inputs, _ = _normalize_sequence(length, inputs, layout, merge_outputs)
if isinstance(inputs, symbol.Symbol):
return self(inputs, [])
else:
return super(DropoutCell, self).unroll(
length, inputs, begin_state=begin_state, layout=layout,
merge_outputs=merge_outputs)
class ModifierCell(BaseRNNCell):
"""Base class for modifier cells. A modifier
cell takes a base cell, apply modifications
on it (e.g. Zoneout), and returns a new cell.
After applying modifiers the base cell should
no longer be called directly. The modifer cell
should be used instead.
"""
def __init__(self, base_cell):
super(ModifierCell, self).__init__()
base_cell._modified = True
self.base_cell = base_cell
@property
def params(self):
self._own_params = False
return self.base_cell.params
@property
def state_info(self):
return self.base_cell.state_info
def begin_state(self, init_sym=symbol.zeros, **kwargs): # pylint: disable=arguments-differ
assert not self._modified, \
"After applying modifier cells (e.g. DropoutCell) the base " \
"cell cannot be called directly. Call the modifier cell instead."
self.base_cell._modified = False
begin = self.base_cell.begin_state(init_sym, **kwargs)
self.base_cell._modified = True
return begin
def unpack_weights(self, args):
return self.base_cell.unpack_weights(args)
def pack_weights(self, args):
return self.base_cell.pack_weights(args)
def __call__(self, inputs, states):
raise NotImplementedError
[docs]class ZoneoutCell(ModifierCell):
"""Apply Zoneout on base cell.
Parameters
----------
base_cell : BaseRNNCell
Cell on whose states to perform zoneout.
zoneout_outputs : float, default 0.
Fraction of the output that gets dropped out during training time.
zoneout_states : float, default 0.
Fraction of the states that gets dropped out during training time.
"""
def __init__(self, base_cell, zoneout_outputs=0., zoneout_states=0.):
assert not isinstance(base_cell, FusedRNNCell), \
"FusedRNNCell doesn't support zoneout. " \
"Please unfuse first."
assert not isinstance(base_cell, BidirectionalCell), \
"BidirectionalCell doesn't support zoneout since it doesn't support step. " \
"Please add ZoneoutCell to the cells underneath instead."
assert not isinstance(base_cell, SequentialRNNCell) or not base_cell._bidirectional, \
"Bidirectional SequentialRNNCell doesn't support zoneout. " \
"Please add ZoneoutCell to the cells underneath instead."
super(ZoneoutCell, self).__init__(base_cell)
self.zoneout_outputs = zoneout_outputs
self.zoneout_states = zoneout_states
self.prev_output = None
def reset(self):
super(ZoneoutCell, self).reset()
self.prev_output = None
def __call__(self, inputs, states):
cell, p_outputs, p_states = self.base_cell, self.zoneout_outputs, self.zoneout_states
next_output, next_states = cell(inputs, states)
mask = lambda p, like: symbol.Dropout(symbol.ones_like(like), p=p)
prev_output = self.prev_output if self.prev_output is not None else symbol.zeros((0, 0))
output = (symbol.where(mask(p_outputs, next_output), next_output, prev_output)
if p_outputs != 0. else next_output)
states = ([symbol.where(mask(p_states, new_s), new_s, old_s) for new_s, old_s in
zip(next_states, states)] if p_states != 0. else next_states)
self.prev_output = output
return output, states
[docs]class ResidualCell(ModifierCell):
"""Adds residual connection as described in Wu et al, 2016
(https://arxiv.org/abs/1609.08144).
Output of the cell is output of the base cell plus input.
Parameters
----------
base_cell : BaseRNNCell
Cell on whose outputs to add residual connection.
"""
def __init__(self, base_cell):
super(ResidualCell, self).__init__(base_cell)
def __call__(self, inputs, states):
output, states = self.base_cell(inputs, states)
output = symbol.elemwise_add(output, inputs, name="%s_plus_residual" % output.name)
return output, states
def unroll(self, length, inputs, begin_state=None, layout='NTC', merge_outputs=None):
self.reset()
self.base_cell._modified = False
outputs, states = self.base_cell.unroll(length, inputs=inputs, begin_state=begin_state,
layout=layout, merge_outputs=merge_outputs)
self.base_cell._modified = True
merge_outputs = isinstance(outputs, symbol.Symbol) if merge_outputs is None else \
merge_outputs
inputs, _ = _normalize_sequence(length, inputs, layout, merge_outputs)
if merge_outputs:
outputs = symbol.elemwise_add(outputs, inputs, name="%s_plus_residual" % outputs.name)
else:
outputs = [symbol.elemwise_add(output_sym, input_sym,
name="%s_plus_residual" % output_sym.name)
for output_sym, input_sym in zip(outputs, inputs)]
return outputs, states
[docs]class BidirectionalCell(BaseRNNCell):
"""Bidirectional RNN cell.
Parameters
----------
l_cell : BaseRNNCell
cell for forward unrolling
r_cell : BaseRNNCell
cell for backward unrolling
params : RNNParams, default None.
Container for weight sharing between cells.
A new RNNParams container is created if `params` is None.
output_prefix : str, default 'bi_'
prefix for name of output
"""
def __init__(self, l_cell, r_cell, params=None, output_prefix='bi_'):
super(BidirectionalCell, self).__init__('', params=params)
self._output_prefix = output_prefix
self._override_cell_params = params is not None
if self._override_cell_params:
assert l_cell._own_params and r_cell._own_params, \
"Either specify params for BidirectionalCell " \
"or child cells, not both."
l_cell.params._params.update(self.params._params)
r_cell.params._params.update(self.params._params)
self.params._params.update(l_cell.params._params)
self.params._params.update(r_cell.params._params)
self._cells = [l_cell, r_cell]
def unpack_weights(self, args):
return _cells_unpack_weights(self._cells, args)
def pack_weights(self, args):
return _cells_pack_weights(self._cells, args)
def __call__(self, inputs, states):
raise NotImplementedError("Bidirectional cannot be stepped. Please use unroll")
@property
def state_info(self):
return _cells_state_info(self._cells)
def begin_state(self, **kwargs): # pylint: disable=arguments-differ
assert not self._modified, \
"After applying modifier cells (e.g. DropoutCell) the base " \
"cell cannot be called directly. Call the modifier cell instead."
return _cells_begin_state(self._cells, **kwargs)
def unroll(self, length, inputs, begin_state=None, layout='NTC', merge_outputs=None):
self.reset()
inputs, axis = _normalize_sequence(length, inputs, layout, False)
if begin_state is None:
begin_state = self.begin_state()
states = begin_state
l_cell, r_cell = self._cells
l_outputs, l_states = l_cell.unroll(length, inputs=inputs,
begin_state=states[:len(l_cell.state_info)],
layout=layout, merge_outputs=merge_outputs)
r_outputs, r_states = r_cell.unroll(length,
inputs=list(reversed(inputs)),
begin_state=states[len(l_cell.state_info):],
layout=layout, merge_outputs=merge_outputs)
if merge_outputs is None:
merge_outputs = (isinstance(l_outputs, symbol.Symbol)
and isinstance(r_outputs, symbol.Symbol))
if not merge_outputs:
if isinstance(l_outputs, symbol.Symbol):
l_outputs = list(symbol.SliceChannel(l_outputs, axis=axis,
num_outputs=length, squeeze_axis=1))
if isinstance(r_outputs, symbol.Symbol):
r_outputs = list(symbol.SliceChannel(r_outputs, axis=axis,
num_outputs=length, squeeze_axis=1))
if merge_outputs:
l_outputs = [l_outputs]
r_outputs = [symbol.reverse(r_outputs, axis=axis)]
else:
r_outputs = list(reversed(r_outputs))
outputs = [symbol.Concat(l_o, r_o, dim=1+merge_outputs,
name=('%sout'%(self._output_prefix) if merge_outputs
else '%st%d'%(self._output_prefix, i)))
for i, l_o, r_o in
zip(range(len(l_outputs)), l_outputs, r_outputs)]
if merge_outputs:
outputs = outputs[0]
states = [l_states, r_states]
return outputs, states
class BaseConvRNNCell(BaseRNNCell):
"""Abstract base class for Convolutional RNN cells"""
def __init__(self, input_shape, num_hidden,
h2h_kernel, h2h_dilate,
i2h_kernel, i2h_stride,
i2h_pad, i2h_dilate,
i2h_weight_initializer, h2h_weight_initializer,
i2h_bias_initializer, h2h_bias_initializer,
activation, prefix='', params=None, conv_layout='NCHW'):
super(BaseConvRNNCell, self).__init__(prefix=prefix, params=params)
# Convolution setting
self._h2h_kernel = h2h_kernel
assert (self._h2h_kernel[0] % 2 == 1) and (self._h2h_kernel[1] % 2 == 1), \
"Only support odd number, get h2h_kernel= %s" % str(h2h_kernel)
self._h2h_pad = (h2h_dilate[0] * (h2h_kernel[0] - 1) // 2,
h2h_dilate[1] * (h2h_kernel[1] - 1) // 2)
self._h2h_dilate = h2h_dilate
self._i2h_kernel = i2h_kernel
self._i2h_stride = i2h_stride
self._i2h_pad = i2h_pad
self._i2h_dilate = i2h_dilate
self._num_hidden = num_hidden
self._input_shape = input_shape
self._conv_layout = conv_layout
self._activation = activation
# Infer state shape
data = symbol.Variable('data')
self._state_shape = symbol.Convolution(data=data,
num_filter=self._num_hidden,
kernel=self._i2h_kernel,
stride=self._i2h_stride,
pad=self._i2h_pad,
dilate=self._i2h_dilate,
layout=conv_layout)
self._state_shape = self._state_shape.infer_shape(data=input_shape)[1][0]
self._state_shape = (0, ) + self._state_shape[1:]
# Get params
self._iW = self.params.get('i2h_weight', init=i2h_weight_initializer)
self._hW = self.params.get('h2h_weight', init=h2h_weight_initializer)
self._iB = self.params.get('i2h_bias', init=i2h_bias_initializer)
self._hB = self.params.get('h2h_bias', init=h2h_bias_initializer)
@property
def _num_gates(self):
return len(self._gate_names)
@property
def state_info(self):
return [{'shape': self._state_shape, '__layout__': self._conv_layout},
{'shape': self._state_shape, '__layout__': self._conv_layout}]
def _conv_forward(self, inputs, states, name):
i2h = symbol.Convolution(name='%si2h'%name,
data=inputs,
num_filter=self._num_hidden*self._num_gates,
kernel=self._i2h_kernel,
stride=self._i2h_stride,
pad=self._i2h_pad,
dilate=self._i2h_dilate,
weight=self._iW,
bias=self._iB,
layout=self._conv_layout)
h2h = symbol.Convolution(name='%sh2h'%name,
data=states[0],
num_filter=self._num_hidden*self._num_gates,
kernel=self._h2h_kernel,
dilate=self._h2h_dilate,
pad=self._h2h_pad,
stride=(1, 1),
weight=self._hW,
bias=self._hB,
layout=self._conv_layout)
return i2h, h2h
def __call__(self, inputs, states):
raise NotImplementedError("BaseConvRNNCell is abstract class for convolutional RNN")
class ConvRNNCell(BaseConvRNNCell):
"""Convolutional RNN cells
Parameters
----------
input_shape : tuple of int
Shape of input in single timestep.
num_hidden : int
Number of units in output symbol.
h2h_kernel : tuple of int, default (3, 3)
Kernel of Convolution operator in state-to-state transitions.
h2h_dilate : tuple of int, default (1, 1)
Dilation of Convolution operator in state-to-state transitions.
i2h_kernel : tuple of int, default (3, 3)
Kernel of Convolution operator in input-to-state transitions.
i2h_stride : tuple of int, default (1, 1)
Stride of Convolution operator in input-to-state transitions.
i2h_pad : tuple of int, default (1, 1)
Pad of Convolution operator in input-to-state transitions.
i2h_dilate : tuple of int, default (1, 1)
Dilation of Convolution operator in input-to-state transitions.
i2h_weight_initializer : str or Initializer
Initializer for the input weights matrix, used for the convolution
transformation of the inputs.
h2h_weight_initializer : str or Initializer
Initializer for the recurrent weights matrix, used for the convolution
transformation of the recurrent state.
i2h_bias_initializer : str or Initializer, default zeros
Initializer for the bias vector.
h2h_bias_initializer : str or Initializer, default zeros
Initializer for the bias vector.
activation : str or Symbol,
default functools.partial(symbol.LeakyReLU, act_type='leaky', slope=0.2)
Type of activation function.
prefix : str, default 'ConvRNN_'
Prefix for name of layers (and name of weight if params is None).
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
conv_layout : str, , default 'NCHW'
Layout of ConvolutionOp
"""
def __init__(self, input_shape, num_hidden,
h2h_kernel=(3, 3), h2h_dilate=(1, 1),
i2h_kernel=(3, 3), i2h_stride=(1, 1),
i2h_pad=(1, 1), i2h_dilate=(1, 1),
i2h_weight_initializer=None, h2h_weight_initializer=None,
i2h_bias_initializer='zeros', h2h_bias_initializer='zeros',
activation=functools.partial(symbol.LeakyReLU, act_type='leaky', slope=0.2),
prefix='ConvRNN_', params=None, conv_layout='NCHW'):
super(ConvRNNCell, self).__init__(input_shape=input_shape, num_hidden=num_hidden,
h2h_kernel=h2h_kernel, h2h_dilate=h2h_dilate,
i2h_kernel=i2h_kernel, i2h_stride=i2h_stride,
i2h_pad=i2h_pad, i2h_dilate=i2h_dilate,
i2h_weight_initializer=i2h_weight_initializer,
h2h_weight_initializer=h2h_weight_initializer,
i2h_bias_initializer=i2h_bias_initializer,
h2h_bias_initializer=h2h_bias_initializer,
activation=activation, prefix=prefix,
params=params, conv_layout=conv_layout)
@property
def _gate_names(self):
return ('',)
def __call__(self, inputs, states):
self._counter += 1
name = '%st%d_'%(self._prefix, self._counter)
i2h, h2h = self._conv_forward(inputs, states, name)
output = self._get_activation(i2h + h2h, self._activation,
name='%sout'%name)
return output, [output]
class ConvLSTMCell(BaseConvRNNCell):
"""Convolutional LSTM network cell.
Reference:
Xingjian et al. NIPS2015
Parameters
----------
input_shape : tuple of int
Shape of input in single timestep.
num_hidden : int
Number of units in output symbol.
h2h_kernel : tuple of int, default (3, 3)
Kernel of Convolution operator in state-to-state transitions.
h2h_dilate : tuple of int, default (1, 1)
Dilation of Convolution operator in state-to-state transitions.
i2h_kernel : tuple of int, default (3, 3)
Kernel of Convolution operator in input-to-state transitions.
i2h_stride : tuple of int, default (1, 1)
Stride of Convolution operator in input-to-state transitions.
i2h_pad : tuple of int, default (1, 1)
Pad of Convolution operator in input-to-state transitions.
i2h_dilate : tuple of int, default (1, 1)
Dilation of Convolution operator in input-to-state transitions.
i2h_weight_initializer : str or Initializer
Initializer for the input weights matrix, used for the convolution
transformation of the inputs.
h2h_weight_initializer : str or Initializer
Initializer for the recurrent weights matrix, used for the convolution
transformation of the recurrent state.
i2h_bias_initializer : str or Initializer, default zeros
Initializer for the bias vector.
h2h_bias_initializer : str or Initializer, default zeros
Initializer for the bias vector.
activation : str or Symbol
default functools.partial(symbol.LeakyReLU, act_type='leaky', slope=0.2)
Type of activation function.
prefix : str, default 'ConvLSTM_'
Prefix for name of layers (and name of weight if params is None).
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
conv_layout : str, , default 'NCHW'
Layout of ConvolutionOp
"""
def __init__(self, input_shape, num_hidden,
h2h_kernel=(3, 3), h2h_dilate=(1, 1),
i2h_kernel=(3, 3), i2h_stride=(1, 1),
i2h_pad=(1, 1), i2h_dilate=(1, 1),
i2h_weight_initializer=None, h2h_weight_initializer=None,
i2h_bias_initializer='zeros', h2h_bias_initializer='zeros',
activation=functools.partial(symbol.LeakyReLU, act_type='leaky', slope=0.2),
prefix='ConvLSTM_', params=None,
conv_layout='NCHW'):
super(ConvLSTMCell, self).__init__(input_shape=input_shape, num_hidden=num_hidden,
h2h_kernel=h2h_kernel, h2h_dilate=h2h_dilate,
i2h_kernel=i2h_kernel, i2h_stride=i2h_stride,
i2h_pad=i2h_pad, i2h_dilate=i2h_dilate,
i2h_weight_initializer=i2h_weight_initializer,
h2h_weight_initializer=h2h_weight_initializer,
i2h_bias_initializer=i2h_bias_initializer,
h2h_bias_initializer=h2h_bias_initializer,
activation=activation, prefix=prefix,
params=params, conv_layout=conv_layout)
@property
def _gate_names(self):
return ['_i', '_f', '_c', '_o']
def __call__(self, inputs, states):
self._counter += 1
name = '%st%d_'%(self._prefix, self._counter)
i2h, h2h = self._conv_forward(inputs, states, name)
gates = i2h + h2h
slice_gates = symbol.SliceChannel(gates, num_outputs=4, axis=self._conv_layout.find('C'),
name="%sslice"%name)
in_gate = symbol.Activation(slice_gates[0], act_type="sigmoid",
name='%si'%name)
forget_gate = symbol.Activation(slice_gates[1], act_type="sigmoid",
name='%sf'%name)
in_transform = self._get_activation(slice_gates[2], self._activation,
name='%sc'%name)
out_gate = symbol.Activation(slice_gates[3], act_type="sigmoid",
name='%so'%name)
next_c = symbol._internal._plus(forget_gate * states[1], in_gate * in_transform,
name='%sstate'%name)
next_h = symbol._internal._mul(out_gate, self._get_activation(next_c, self._activation),
name='%sout'%name)
return next_h, [next_h, next_c]
class ConvGRUCell(BaseConvRNNCell):
"""Convolutional Gated Rectified Unit (GRU) network cell.
Parameters
----------
input_shape : tuple of int
Shape of input in single timestep.
num_hidden : int
Number of units in output symbol.
h2h_kernel : tuple of int, default (3, 3)
Kernel of Convolution operator in state-to-state transitions.
h2h_dilate : tuple of int, default (1, 1)
Dilation of Convolution operator in state-to-state transitions.
i2h_kernel : tuple of int, default (3, 3)
Kernel of Convolution operator in input-to-state transitions.
i2h_stride : tuple of int, default (1, 1)
Stride of Convolution operator in input-to-state transitions.
i2h_pad : tuple of int, default (1, 1)
Pad of Convolution operator in input-to-state transitions.
i2h_dilate : tuple of int, default (1, 1)
Dilation of Convolution operator in input-to-state transitions.
i2h_weight_initializer : str or Initializer
Initializer for the input weights matrix, used for the convolution
transformation of the inputs.
h2h_weight_initializer : str or Initializer
Initializer for the recurrent weights matrix, used for the convolution
transformation of the recurrent state.
i2h_bias_initializer : str or Initializer, default zeros
Initializer for the bias vector.
h2h_bias_initializer : str or Initializer, default zeros
Initializer for the bias vector.
activation : str or Symbol,
default functools.partial(symbol.LeakyReLU, act_type='leaky', slope=0.2)
Type of activation function.
prefix : str, default 'ConvGRU_'
Prefix for name of layers (and name of weight if params is None).
params : RNNParams, default None
Container for weight sharing between cells. Created if None.
conv_layout : str, , default 'NCHW'
Layout of ConvolutionOp
"""
def __init__(self, input_shape, num_hidden,
h2h_kernel=(3, 3), h2h_dilate=(1, 1),
i2h_kernel=(3, 3), i2h_stride=(1, 1),
i2h_pad=(1, 1), i2h_dilate=(1, 1),
i2h_weight_initializer=None, h2h_weight_initializer=None,
i2h_bias_initializer='zeros', h2h_bias_initializer='zeros',
activation=functools.partial(symbol.LeakyReLU, act_type='leaky', slope=0.2),
prefix='ConvGRU_', params=None, conv_layout='NCHW'):
super(ConvGRUCell, self).__init__(input_shape=input_shape, num_hidden=num_hidden,
h2h_kernel=h2h_kernel, h2h_dilate=h2h_dilate,
i2h_kernel=i2h_kernel, i2h_stride=i2h_stride,
i2h_pad=i2h_pad, i2h_dilate=i2h_dilate,
i2h_weight_initializer=i2h_weight_initializer,
h2h_weight_initializer=h2h_weight_initializer,
i2h_bias_initializer=i2h_bias_initializer,
h2h_bias_initializer=h2h_bias_initializer,
activation=activation, prefix=prefix,
params=params, conv_layout=conv_layout)
@property
def _gate_names(self):
return ['_r', '_z', '_o']
def __call__(self, inputs, states):
self._counter += 1
seq_idx = self._counter
name = '%st%d_' % (self._prefix, seq_idx)
i2h, h2h = self._conv_forward(inputs, states, name)
i2h_r, i2h_z, i2h = symbol.SliceChannel(i2h, num_outputs=3, name="%s_i2h_slice" % name)
h2h_r, h2h_z, h2h = symbol.SliceChannel(h2h, num_outputs=3, name="%s_h2h_slice" % name)
reset_gate = symbol.Activation(i2h_r + h2h_r, act_type="sigmoid",
name="%s_r_act" % name)
update_gate = symbol.Activation(i2h_z + h2h_z, act_type="sigmoid",
name="%s_z_act" % name)
next_h_tmp = self._get_activation(i2h + reset_gate * h2h, self._activation,
name="%s_h_act" % name)
next_h = symbol._internal._plus((1. - update_gate) * next_h_tmp, update_gate * states[0],
name='%sout' % name)
return next_h, [next_h]
