def Pooling(op, # PoolingType_Max or _Average
filter_shape, # e.g. (3,3)
strides=1,
pad=False):
x = Placeholder(name='pooling_arg')
apply_x = pooling (x, op, filter_shape, strides=_as_tuple(strides), auto_padding=_as_tuple(pad))
if op == PoolingType_Average:
op_name = 'AveragePooling'
elif op == PoolingType_Max:
op_name = 'MaxPooling'
else:
raise ValueError('Pooling: op must be PoolingType_Max or PoolingType_average')
return Block(apply_x, op_name)
def Pooling(op, # PoolingType_Max or _Average
filter_shape, # e.g. (3,3)
strides=1,
pad=False):
x = Placeholder(name='pooling_arg')
apply_x = pooling (x, op, filter_shape, strides=_as_tuple(strides), auto_padding=_as_tuple(pad))
if op == PoolingType_Average:
op_name = 'AveragePooling'
elif op == PoolingType_Max:
op_name = 'MaxPooling'
else:
raise ValueError('Pooling: op must be PoolingType_Max or PoolingType_average')
return Block(apply_x, op_name)
def Convolution(filter_shape, # e.g. (3,3)
num_filters=None, # e.g. 64 or None (which means 1 channel and don't add a dimension_
activation=activation_default_or_None,
init=init_default_or_glorot_uniform,
pad=pad_default_or_False,
strides=1,
sharing=True, # (must be True currently)
bias=bias_default_or_True,
init_bias=init_bias_default_or_0,
reduction_rank=1, # (must be 1 currently)
transpose=False, # (must be False currently)
max_temp_mem_size_in_samples=0):
#UntestedBranchError("Convolution")
activation = _resolve_activation(activation)
pad = pad if _is_given(pad ) else _current_default_options.pad
bias = bias if _is_given(bias) else _current_default_options.bias
# TODO: there must be a Python trick to do this as a function call on locals or so
if reduction_rank != 1:
NotImplementedError("Convolution: reduction_rank other than 1 currently not supported")
if transpose:
NotImplementedError("Convolution: transpose option currently not supported")
if not sharing:
NotImplementedError("Convolution: sharing option currently must be True")
output_channels_shape = _as_tuple(num_filters)
output_rank = len(output_channels_shape)
filter_rank = len(filter_shape)
kernel_shape = _INFERRED * reduction_rank + filter_shape # kernel := filter plus reductionDims
# parameters bound to this Function
#init_kernel = glorot_uniform(filter_rank=-filter_rank, output_rank=1)
init_kernel = _initializer_for(init, Record(filter_rank=filter_rank, output_rank=-1))
# BUGBUG: It is very confusing that output_rank is negative, esp. since that means count from the start. Solution: add a flag
W = Parameter(output_channels_shape + kernel_shape, init=init_kernel, name='W') # (K, C, H, W) aka [ W x H x C x K ]
b = Parameter(output_channels_shape + (1,) * len(filter_shape), init=init_bias, name='b') if bias else None # (K, 1, 1) aka [ 1 x 1 x K ]
# expression
x = Placeholder(name='convolution_arg')
# TODO: update the parameter order of convolution() to match the optional ones as in here? (options order matches Keras)
apply_x = convolution (W, x,
strides=_as_tuple(strides),
sharing=_as_tuple(sharing),
auto_padding=_as_tuple(pad),
# TODO: can we rename auto_padding to pad?
transpose=transpose,
max_temp_mem_size_in_samples=max_temp_mem_size_in_samples)
if bias:
apply_x = apply_x + b
apply_x = apply_x >> activation
return Block(apply_x, 'Convolution', Record(W=W, b=b))
def Convolution(filter_shape, # e.g. (3,3)
num_filters=None, # e.g. 64 or None (which means 1 channel and don't add a dimension_
activation=activation_default_or_None,
init=init_default_or_glorot_uniform,
pad=pad_default_or_False,
strides=1,
sharing=True, # (must be True currently)
bias=bias_default_or_True,
init_bias=init_bias_default_or_0,
reduction_rank=1, # (must be 1 currently)
transpose=False, # (must be False currently)
max_temp_mem_size_in_samples=0):
#UntestedBranchError("Convolution")
activation = _resolve_activation(activation)
pad = pad if _is_given(pad ) else _current_default_options.pad
bias = bias if _is_given(bias) else _current_default_options.bias
# TODO: there must be a Python trick to do this as a function call on locals or so
if reduction_rank != 1:
NotImplementedError("Convolution: reduction_rank other than 1 currently not supported")
if transpose:
NotImplementedError("Convolution: transpose option currently not supported")
if not sharing:
NotImplementedError("Convolution: sharing option currently must be True")
output_channels_shape = _as_tuple(num_filters)
output_rank = len(output_channels_shape)
filter_rank = len(filter_shape)
kernel_shape = _INFERRED * reduction_rank + filter_shape # kernel := filter plus reductionDims
# parameters bound to this Function
#init_kernel = glorot_uniform(filter_rank=-filter_rank, output_rank=1)
init_kernel = _initializer_for(init, Record(filter_rank=filter_rank, output_rank=-1))
# BUGBUG: It is very confusing that output_rank is negative, esp. since that means count from the start. Solution: add a flag
W = Parameter(output_channels_shape + kernel_shape, init=init_kernel, name='W') # (K, C, H, W) aka [ W x H x C x K ]
b = Parameter(output_channels_shape + (1,) * len(filter_shape), init=init_bias, name='b') if bias else None # (K, 1, 1) aka [ 1 x 1 x K ]
# expression
x = Placeholder(name='convolution_arg')
# TODO: update the parameter order of convolution() to match the optional ones as in here? (options order matches Keras)
apply_x = convolution (W, x,
strides=_as_tuple(strides),
sharing=_as_tuple(sharing),
auto_padding=_as_tuple(pad),
# TODO: can we rename auto_padding to pad?
transpose=transpose,
max_temp_mem_size_in_samples=max_temp_mem_size_in_samples)
if bias:
apply_x = apply_x + b
apply_x = apply_x >> activation
return Block(apply_x, 'Convolution', Record(W=W, b=b))
def Embedding(shape=None, init=None, weights=None):
if init is not None or weights is not None:
raise ValueError('Embedding: init and weights options are mutually exclusive')
# parameters bound to this Function:
# no weights given: learn the embedding
if weights is None:
if shape is None:
raise ValueError('Embedding: output shape must be specified')
if init is None:
init = init_default_or_glorot_uniform
shape = _as_tuple(shape)
weight_shape = _INFERRED + shape
E = Parameter(weight_shape, init=init, name='E')
# weights given: use them as constant
else:
UntestedBranchError("Embedding, from constant")
import numpy as np
if not isinstance(weights, array): # TODO: is this the correct test for a numpy array
UntestedBranchError("Embedding, from constant that is not an array")
# TODO: can 'weights' be a CNTK object? Then how to do this?
raise ValueError('Embedding: weights must be a numpy array')
weight_shape = np.shape(weights)
if shape is not None: # user may give shape, then it must match
if len(shape) >= len(weight_shape) or weight_shape[-len(shape):] != shape:
raise ValueError('Embedding: shape parameter must match weights')
E = Constant(weights, name='E')
# expression
x = Placeholder(name='embedding_arg')
apply_x = times(x, E)
return Block(apply_x, 'Embedding', Record(E=E))
def Embedding(shape=None, init=None, weights=None):
if init is not None or weights is not None:
raise ValueError('Embedding: init and weights options are mutually exclusive')
# parameters bound to this Function:
# no weights given: learn the embedding
if weights is None:
if shape is None:
raise ValueError('Embedding: output shape must be specified')
if init is None:
init = init_default_or_glorot_uniform
shape = _as_tuple(shape)
weight_shape = _INFERRED + shape
E = Parameter(weight_shape, init=init, name='E')
# weights given: use them as constant
else:
UntestedBranchError("Embedding, from constant")
import numpy as np
if not isinstance(weights, array): # TODO: is this the correct test for a numpy array
UntestedBranchError("Embedding, from constant that is not an array")
# TODO: can 'weights' be a CNTK object? Then how to do this?
raise ValueError('Embedding: weights must be a numpy array')
weight_shape = np.shape(weights)
if shape is not None: # user may give shape, then it must match
if len(shape) >= len(weight_shape) or weight_shape[-len(shape):] != shape:
raise ValueError('Embedding: shape parameter must match weights')
E = Constant(weights, name='E')
# expression
x = Placeholder(name='embedding_arg')
apply_x = times(x, E)
return Block(apply_x, 'Embedding', Record(E=E))
def Linear(shape, _inf, bias=True, init=_default_initializer, init_bias=0, input_rank=None, map_rank=None):
out_shape = _as_tuple(shape)
# TODO: implement the full semantics of the BrainScript code
#inputShape =
# if BS.Constants.IsNone (inputRank) then Inferred # not given: one Inferred, which will get expanded
# else if !BS.Constants.IsNone (mapRank) then Fail ("'inputRank' and 'mapRank' cannot be specified at the same time.")
# else Repeat (inputRank, Inferred)
#W = ParameterTensor {_ConcatArrays (outDim, inputShape), init=init, initValueScale=initValueScale}
#b = ParameterTensor {outDim, initValue=0}
#outputRank = Length (_AsArray (outDim)) # support outputs with tensor layouts
#inferInputRankToMap =
# if !BS.Constants.IsNone (inputRank) then -1 # means not specified
# else if BS.Constants.IsNone (mapRank) then 0 # default to 'use all input dims'
# else mapRank
#apply (x) =
# if bias
# then Times (W, x, outputRank=outputRank, inferInputRankToMap=inferInputRankToMap) + b
# else Times (W, x, outputRank=outputRank, inferInputRankToMap=inferInputRankToMap)
W = Parameter(_inf.shape + out_shape, init=init , name='W')
b = Parameter( out_shape, init=init_bias, name='b') if bias else None
x = Placeholder(_inf=_inf, name='linear_arg')
apply_x = Function.__matmul__(x, W) + b if bias else \
Function.__matmul__(x, W)
_name_and_extend_Function(apply_x, 'Linear')
return apply_x
def Recurrence(over, go_backwards=False, initial_state=initial_state_default_or_None):
# helper to compute previous value
# can take a single Variable/Function or a tuple
initial_state = initial_state if _is_given(initial_state) else _current_default_options.initial_state
# if initial state is given and a numeric constant, then turn it into a Constant() object
if np.isscalar(initial_state):
initial_state = Constant(initial_state, shape=(1)) # TODO: This should be automatically done inside the API.
def previous_hook(state):
if isinstance (state, tuple): # if multiple then apply to each element
return tuple([previous_hook(s) for s in state])
# not a tuple: must be a 'scalar', i.e. a single element
return past_value (state, initial_state) if not go_backwards else \
future_value(state, initial_state)
x = Placeholder(name='recurrence_arg')
state_forward = over.create_placeholder() # create a placeholder or a tuple of placeholders
prev_state = previous_hook(state_forward) # delay (h, c)
f_x_h_c = over(x, prev_state) # apply the recurrent over
# this returns a Function (x, (h_prev, c_prev)) -> (h, c)
h_c = f_x_h_c.outputs
replacements = { value_forward: value for (value_forward, value) in zip(list(_as_tuple(state_forward)), h_c) }
f_x_h_c.replace_placeholders(replacements) # resolves state_forward := h_c
h = f_x_h_c.outputs[0] # 'h' is a Variable (the output of a Function that computed it)
if _trace_layers:
_log_node(h)
_log_node(combine([h.owner]))
apply_x = combine([h]) # the Function that yielded 'h', so we get to know its inputs
# apply_x is a Function x -> h
return Block(apply_x, 'Recurrence', Record(over=over))
def Recurrence(over, go_backwards=False, initial_state=initial_state_default_or_None):
# helper to compute previous value
# can take a single Variable/Function or a tuple
initial_state = initial_state if _is_given(initial_state) else _current_default_options.initial_state
# if initial state is given and a numeric constant, then turn it into a Constant() object
if np.isscalar(initial_state):
initial_state = Constant(initial_state, shape=(1)) # TODO: This should be automatically done inside the API.
def previous_hook(state):
if isinstance (state, tuple): # if multiple then apply to each element
return tuple([previous_hook(s) for s in state])
# not a tuple: must be a 'scalar', i.e. a single element
return past_value (state, initial_state) if not go_backwards else \
future_value(state, initial_state)
x = Placeholder(name='recurrence_arg')
state_forward = over.create_placeholder() # create a placeholder or a tuple of placeholders
prev_state = previous_hook(state_forward) # delay (h, c)
f_x_h_c = over(x, prev_state) # apply the recurrent over
# this returns a Function (x, (h_prev, c_prev)) -> (h, c)
h_c = f_x_h_c.outputs
replacements = { value_forward: value for (value_forward, value) in zip(list(_as_tuple(state_forward)), h_c) }
f_x_h_c.replace_placeholders(replacements) # resolves state_forward := h_c
h = f_x_h_c.outputs[0] # 'h' is a Variable (the output of a Function that computed it)
if _trace_layers:
_log_node(h)
_log_node(combine([h.owner]))
apply_x = combine([h]) # the Function that yielded 'h', so we get to know its inputs
# apply_x is a Function x -> h
return Block(apply_x, 'Recurrence', Record(over=over))
def Placeholder(_inf, name='placeholder'):
p = placeholder_variable(shape=_as_tuple(_inf.shape),
dynamic_axes=_inf.axis,
name=name)
_name_node(p, name)
if _trace_layers:
print("new " + _node_description(p))
return p
def Dense(shape,
init=init_default_or_glorot_uniform,
activation=activation_default_or_None,
input_rank=None,
map_rank=None,
bias=bias_default_or_True,
init_bias=init_bias_default_or_0):
activation = _resolve_activation(activation)
bias = bias if _is_given(bias) else _current_default_options.bias
output_shape = _as_tuple(shape)
if input_rank is not None and map_rank is not None:
raise ValueError(
"Dense: input_rank and map_rank cannot be specified at the same time."
)
# determine meaning of axes
# W gets dimension (input_shape + shape)
# where input_shape is determined as:
# - by default, equal to the dimensions of the input passed to Dense()
# - if input_rank is given, then the last 'input_rank' dimensions of the input (all others are not reduced over)
# - if map_rank is given, then the all but the first 'map_rank' dimensions of the input (those are not reduced over)
# where input_rank and map_rank are mutuallly exclusive.
#output_rank = -len(output_shape) # support outputs with tensor layouts
# BUGBUG: Should this be a negative number now, since output is the last axis in Python?
output_rank = len(output_shape) # support outputs with tensor layouts
# If input_rank not given then pass a single _INFERRED; map_rank if given will determine the input_rank.
# The dimension inference may still create multiple axes.
input_shape = _INFERRED * (input_rank if input_rank is not None else 1)
if input_rank is not None:
UntestedBranchError("Dense, input_rank option not implemented")
infer_input_rank_to_map = -1 # means map_rank is not specified; input_rank rules
elif map_rank is None:
infer_input_rank_to_map = 0 # neither given: default to 'infer W to use all input dims'
else:
UntestedBranchError("Dense, map_rank option not implemented")
infer_input_rank_to_map = map_rank # infer W to use all input dims except the first static 'map_rank' ones
# parameters bound to this Function
init_weights = _initializer_for(init, Record(output_rank=output_rank))
W = Parameter(input_shape + output_shape, init=init_weights, name='W')
b = Parameter(output_shape, init=init_bias, name='b') if bias else None
# expression of this function
x = Placeholder(name='dense_arg')
apply_x = times(x,
W,
output_rank=output_rank,
infer_input_rank_to_map=infer_input_rank_to_map)
if b:
apply_x = apply_x + b
apply_x = apply_x >> activation
return Block(apply_x, 'Dense', Record(W=W, b=b))
def Embedding(shape, _inf, weights=None, init=_default_initializer, transpose=False):
shape = _as_tuple(shape)
full_shape = (shape + _inf.shape) if transpose else (_inf.shape + shape)
if weights is None: # no weights given: learn the embedding
E = Parameter(full_shape, init=init, name='E')
else: # weights given: use them as constant
UntestedBranchError("Embedding, from constant")
E = Constant(full_shape, init=weights, name='E') # TODO: can 'weights' be a CNTK object already? Then how to do this?
x = Placeholder(_inf=_inf, name='embedding_arg')
apply_x = Function.__matmul__(E, x) if transpose else \
Function.__matmul__(x, E) # x is expected to be sparse one-hot
_name_and_extend_Function(apply_x, 'Embedding')
return apply_x
def Dense(shape, init=init_default_or_glorot_uniform, activation=activation_default_or_None,
input_rank=None, map_rank=None,
bias=bias_default_or_True, init_bias=init_bias_default_or_0):
activation = _resolve_activation(activation)
bias = bias if _is_given(bias) else _current_default_options.bias
output_shape = _as_tuple(shape)
if input_rank is not None and map_rank is not None:
raise ValueError("Dense: input_rank and map_rank cannot be specified at the same time.")
# determine meaning of axes
# W gets dimension (input_shape + shape)
# where input_shape is determined as:
# - by default, equal to the dimensions of the input passed to Dense()
# - if input_rank is given, then the last 'input_rank' dimensions of the input (all others are not reduced over)
# - if map_rank is given, then the all but the first 'map_rank' dimensions of the input (those are not reduced over)
# where input_rank and map_rank are mutuallly exclusive.
#output_rank = -len(output_shape) # support outputs with tensor layouts
# BUGBUG: Should this be a negative number now, since output is the last axis in Python?
output_rank = len(output_shape) # support outputs with tensor layouts
# If input_rank not given then pass a single _INFERRED; map_rank if given will determine the input_rank.
# The dimension inference may still create multiple axes.
input_shape = _INFERRED * (input_rank if input_rank is not None else 1)
if input_rank is not None:
UntestedBranchError("Dense, input_rank option not implemented")
infer_input_rank_to_map = -1 # means map_rank is not specified; input_rank rules
elif map_rank is None:
infer_input_rank_to_map = 0 # neither given: default to 'infer W to use all input dims'
else:
UntestedBranchError("Dense, map_rank option not implemented")
infer_input_rank_to_map = map_rank # infer W to use all input dims except the first static 'map_rank' ones
# parameters bound to this Function
init_weights = _initializer_for(init, Record(output_rank=output_rank))
W = Parameter(input_shape + output_shape, init=init_weights, name='W')
b = Parameter( output_shape, init=init_bias, name='b') if bias else None
# expression of this function
x = Placeholder(name='dense_arg')
apply_x = times(x, W, output_rank=output_rank, infer_input_rank_to_map=infer_input_rank_to_map)
if b:
apply_x = apply_x + b
apply_x = apply_x >> activation
return Block(apply_x, 'Dense', Record(W=W, b=b))
def _RecurrentBlock(type, shape, cell_shape, activation, use_peepholes,
init, init_bias,
enable_self_stabilization,
name=''):
'''
Helper to create a recurrent block of type 'LSTM', 'GRU', or RNNUnit.
'''
has_projection = cell_shape is not None
shape = _as_tuple(shape)
cell_shape = _as_tuple(cell_shape) if cell_shape is not None else shape
if len(shape) != 1 or len(cell_shape) != 1:
raise ValueError("%s: shape and cell_shape must be vectors (rank-1 tensors)" % type)
# otherwise we'd need to fix slicing and Param initializers
stack_axis = -1 # for efficient computation, we stack multiple variables (along the fastest-changing one, to match BS)
# determine stacking dimensions
cell_shape_list = list(cell_shape)
stacked_dim = cell_shape_list[stack_axis]
cell_shape_list[stack_axis] = stacked_dim * {
'RNNUnit': 1,
'GRU': 3,
'LSTM': 4
}[type]
cell_shape_stacked = tuple(cell_shape_list) # patched dims with stack_axis duplicated 4 times
cell_shape_list[stack_axis] = stacked_dim * {
'RNNUnit': 1,
'GRU': 2,
'LSTM': 4
}[type]
cell_shape_stacked_H = tuple(cell_shape_list) # patched dims with stack_axis duplicated 4 times
# parameters
b = Parameter( cell_shape_stacked, init=init_bias, name='b') # bias
W = Parameter(_INFERRED + cell_shape_stacked, init=init, name='W') # input
H = Parameter(shape + cell_shape_stacked_H, init=init, name='H') # hidden-to-hidden
H1 = Parameter(shape + cell_shape, init=init, name='H1') if type == 'GRU' else None # hidden-to-hidden
Ci = Parameter( cell_shape, init=init, name='Ci') if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Cf = Parameter( cell_shape, init=init, name='Cf') if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Co = Parameter( cell_shape, init=init, name='Co') if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Wmr = Parameter(cell_shape + shape, init=init, name='P') if has_projection else None # final projection
# each use of a stabilizer layer must get its own instance
Sdh = Stabilizer(enable_self_stabilization=enable_self_stabilization, name='dh_stabilizer')
Sdc = Stabilizer(enable_self_stabilization=enable_self_stabilization, name='dc_stabilizer')
Sct = Stabilizer(enable_self_stabilization=enable_self_stabilization, name='c_stabilizer')
Sht = Stabilizer(enable_self_stabilization=enable_self_stabilization, name='P_stabilizer')
# define the model function itself
# general interface for Recurrence():
# (all previous outputs delayed, input) --> (outputs and state)
# where
# - the first output is the main output, e.g. 'h' for LSTM
# - the remaining outputs, if any, are additional state
# - if for some reason output != state, then output is still fed back and should just be ignored by the recurrent block
# LSTM model function
# in this case:
# (dh, dc, x) --> (h, c)
def lstm(dh, dc, x):
dhs = Sdh(dh) # previous values, stabilized
dcs = Sdc(dc)
# note: input does not get a stabilizer here, user is meant to do that outside
# projected contribution from input(s), hidden, and bias
proj4 = b + times(x, W) + times(dhs, H)
it_proj = slice (proj4, stack_axis, 0*stacked_dim, 1*stacked_dim) # split along stack_axis
bit_proj = slice (proj4, stack_axis, 1*stacked_dim, 2*stacked_dim)
ft_proj = slice (proj4, stack_axis, 2*stacked_dim, 3*stacked_dim)
ot_proj = slice (proj4, stack_axis, 3*stacked_dim, 4*stacked_dim)
# helper to inject peephole connection if requested
def peep(x, c, C):
return x + C * c if use_peepholes else x
it = sigmoid (peep (it_proj, dcs, Ci)) # input gate(t)
# TODO: should both activations be replaced?
bit = it * activation (bit_proj) # applied to tanh of input network
ft = sigmoid (peep (ft_proj, dcs, Cf)) # forget-me-not gate(t)
bft = ft * dc # applied to cell(t-1)
ct = bft + bit # c(t) is sum of both
ot = sigmoid (peep (ot_proj, Sct(ct), Co)) # output gate(t)
ht = ot * activation (ct) # applied to tanh(cell(t))
c = ct # cell value
h = times(Sht(ht), Wmr) if has_projection else \
ht
# returns the new state as a tuple with names but order matters
return (Function.NamedOutput(h=h), Function.NamedOutput(c=c))
# GRU model function
# in this case:
# (dh, x) --> (h)
# e.g. https://en.wikipedia.org/wiki/Gated_recurrent_unit
def gru(dh, x):
dhs = Sdh(dh) # previous value, stabilized
# note: input does not get a stabilizer here, user is meant to do that outside
# projected contribution from input(s), hidden, and bias
projx3 = b + times(x, W)
projh2 = times(dhs, H)
zt_proj = slice (projx3, stack_axis, 0*stacked_dim, 1*stacked_dim) + slice (projh2, stack_axis, 0*stacked_dim, 1*stacked_dim)
rt_proj = slice (projx3, stack_axis, 1*stacked_dim, 2*stacked_dim) + slice (projh2, stack_axis, 1*stacked_dim, 2*stacked_dim)
ct_proj = slice (projx3, stack_axis, 2*stacked_dim, 3*stacked_dim)
zt = sigmoid (zt_proj) # update gate z(t)
rt = sigmoid (rt_proj) # reset gate r(t)
rs = dhs * rt # "cell" c
ct = activation (ct_proj + times(rs, H1))
ht = (1 - zt) * ct + zt * dhs # hidden state ht / output
# for comparison: CUDNN_GRU
# i(t) = sigmoid(W_i x(t) + R_i h(t-1) + b_Wi + b_Ru)
# r(t) = sigmoid(W_r x(t) + R_r h(t-1) + b_Wr + b_Rr) --same up to here
# h'(t) = tanh(W_h x(t) + r(t) .* (R_h h(t-1)) + b_Wh + b_Rh) --r applied after projection? Would make life easier!
# h(t) = (1 - i(t) .* h'(t)) + i(t) .* h(t-1) --TODO: need to confirm bracketing with NVIDIA
h = times(Sht(ht), Wmr) if has_projection else \
ht
# returns the new state as a tuple with names but order matters
return Function.NamedOutput(h=h)
def rnn(dh, x):
dhs = Sdh(dh) # previous value, stabilized
ht = activation (times(x, W) + times(dhs, H) + b)
h = times(Sht(ht), Wmr) if has_projection else \
ht
return Function.NamedOutput(h=h)
function = {
'RNNUnit': rnn,
'GRU': gru,
'LSTM': lstm
}[type]
# return the corresponding lambda as a CNTK Function
return BlockFunction(type, name)(function)
def LSTM(shape, cell_shape=None, use_peepholes=use_peepholes_default_or_False,
init=init_default_or_glorot_uniform, init_bias=init_bias_default_or_0,
enable_self_stabilization=enable_self_stabilization_default_or_False): # (x, (h, c))
use_peepholes = use_peepholes if _is_given(use_peepholes) else _current_default_options.use_peepholes
enable_self_stabilization = enable_self_stabilization if _is_given(enable_self_stabilization) else _current_default_options.enable_self_stabilization
has_projection = cell_shape is not None
has_aux = False
if has_aux:
UntestedBranchError("LSTM, has_aux option")
shape = _as_tuple(shape)
cell_shape = _as_tuple(cell_shape) if cell_shape is not None else shape
if len(shape) != 1 or len(cell_shape) != 1:
raise ValueError("LSTM: shape and cell_shape must be vectors (rank-1 tensors)")
# otherwise we'd need to fix slicing and Param initializers
stack_axis = -1 # stacking along the fastest-changing one, to match BS
# determine stacking dimensions
cell_shape_list = list(cell_shape)
stacked_dim = cell_shape_list[0]
cell_shape_list[stack_axis] = stacked_dim*4
cell_shape_stacked = tuple(cell_shape_list) # patched dims with stack_axis duplicated 4 times
# parameters
b = Parameter( cell_shape_stacked, init=init_bias, name='b') # a bias
W = Parameter(_INFERRED + cell_shape_stacked, init=init, name='W') # input
A = Parameter(_INFERRED + cell_shape_stacked, init=init, name='A') if has_aux else None # aux input (optional)
H = Parameter(shape + cell_shape_stacked, init=init, name='H') # hidden-to-hidden
Ci = Parameter( cell_shape, init=init, name='Ci') if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Cf = Parameter( cell_shape, init=init, name='Cf') if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Co = Parameter( cell_shape, init=init, name='Co') if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Wmr = Parameter(cell_shape + shape, init=init) if has_projection else None # final projection
Sdh = Stabilizer() if enable_self_stabilization else identity
Sdc = Stabilizer() if enable_self_stabilization else identity
Sct = Stabilizer() if enable_self_stabilization else identity
Sht = Stabilizer() if enable_self_stabilization else identity
def create_hc_placeholder():
# we pass the known dimensions here, which makes dimension inference easier
return (Placeholder(shape=shape, name='hPh'), Placeholder(shape=cell_shape, name='cPh')) # (h, c)
# parameters to model function
x = Placeholder(name='lstm_block_arg')
prev_state = create_hc_placeholder()
# formula of model function
dh, dc = prev_state
dhs = Sdh(dh) # previous values, stabilized
dcs = Sdc(dc)
# note: input does not get a stabilizer here, user is meant to do that outside
# projected contribution from input(s), hidden, and bias
proj4 = b + times(x, W) + times(dhs, H) + times(aux, A) if has_aux else \
b + times(x, W) + times(dhs, H)
it_proj = slice (proj4, stack_axis, 0*stacked_dim, 1*stacked_dim) # split along stack_axis
bit_proj = slice (proj4, stack_axis, 1*stacked_dim, 2*stacked_dim)
ft_proj = slice (proj4, stack_axis, 2*stacked_dim, 3*stacked_dim)
ot_proj = slice (proj4, stack_axis, 3*stacked_dim, 4*stacked_dim)
# add peephole connection if requested
def peep(x, c, C):
return x + C * c if use_peepholes else x
it = sigmoid (peep (it_proj, dcs, Ci)) # input gate(t)
bit = it * tanh (bit_proj) # applied to tanh of input network
ft = sigmoid (peep (ft_proj, dcs, Cf)) # forget-me-not gate(t)
bft = ft * dc # applied to cell(t-1)
ct = bft + bit # c(t) is sum of both
ot = sigmoid (peep (ot_proj, Sct(ct), Co)) # output gate(t)
ht = ot * tanh (ct) # applied to tanh(cell(t))
c = ct # cell value
h = times(Sht(ht), Wmr) if has_projection else \
ht
_name_node(h, 'h')
if _trace_layers:
_log_node(h) # this looks right
_name_node(c, 'c')
# TODO: figure out how to do scoping, and also rename all the apply... to expression
apply_x_h_c = combine ([h, c])
# return to caller a helper function to create placeholders for recurrence
# Note that this function will only exist in the object returned here, but not any cloned version of it.
apply_x_h_c.create_placeholder = create_hc_placeholder
#return Block(apply_x_h_c, 'LSTM') # BUGBUG: fails with "RuntimeError: A Function instance with more than one output cannot be implicitly converted to a Variable"
return apply_x_h_c
def _Infer(shape, axis):
from cntk.utils import Record, _as_tuple
return Record(shape=_as_tuple(shape), axis=axis, with_shape = lambda new_shape: _Infer(new_shape, axis))
def LSTM(shape,
_inf,
cell_shape=None,
use_peepholes=False,
init=_default_initializer,
init_bias=0,
enable_self_stabilization=False): # (x, (h, c))
has_projection = cell_shape is not None
has_aux = False
if has_aux:
UntestedBranchError("LSTM, has_aux option")
if enable_self_stabilization:
UntestedBranchError("LSTM, enable_self_stabilization option")
shape = _as_tuple(shape)
cell_shape = _as_tuple(cell_shape) if cell_shape is not None else shape
#stack_axis = -1 #
stack_axis = 0 # BUGBUG: should be -1, i.e. the fastest-changing one, to match BS
# determine stacking dimensions
cell_shape_list = list(cell_shape)
stacked_dim = cell_shape_list[0]
cell_shape_list[stack_axis] = stacked_dim * 4
cell_shape_stacked = tuple(
cell_shape_list) # patched dims with stack_axis duplicated 4 times
# parameters
b = Parameter(cell_shape_stacked, init=init_bias, name='b') # a bias
W = Parameter(_inf.shape + cell_shape_stacked, init=init,
name='W') # input
A = Parameter(_inf.shape + cell_shape_stacked, init=init,
name='A') if has_aux else None # aux input (optional)
H = Parameter(shape + cell_shape_stacked, init=init,
name='H') # hidden-to-hidden
Ci = Parameter(
cell_shape, init=init, name='Ci'
) if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Cf = Parameter(
cell_shape, init=init, name='Cf'
) if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Co = Parameter(
cell_shape, init=init, name='Co'
) if use_peepholes else None # cell-to-hiddden {note: applied elementwise}
Wmr = ParameterTensor(
cell_shape + shape, init=init, init_value_scale=init_value_scale
) if has_projection else None # final projection
Sdh = Stabilizer(_inf=_inf.with_shape(
shape)) if enable_self_stabilization else Identity(
_inf=_inf.with_shape(shape))
Sdc = Stabilizer(_inf=_inf.with_shape(
cell_shape)) if enable_self_stabilization else Identity(
_inf=_inf.with_shape(cell_shape))
Sct = Stabilizer(_inf=_inf.with_shape(
cell_shape)) if enable_self_stabilization else Identity(
_inf=_inf.with_shape(cell_shape))
Sht = Stabilizer(_inf=_inf.with_shape(
shape)) if enable_self_stabilization else Identity(
_inf=_inf.with_shape(shape))
def create_hc_placeholder():
return (Placeholder(_inf=_inf.with_shape(shape), name='hPh'),
Placeholder(_inf=_inf.with_shape(cell_shape),
name='cPh')) # (h, c)
# parameters to model function
x = Placeholder(_inf=_inf, name='lstm_block_arg')
prev_state = create_hc_placeholder()
# formula of model function
dh, dc = prev_state
dhs = Sdh(dh) # previous values, stabilized
dcs = Sdc(dc)
# note: input does not get a stabilizer here, user is meant to do that outside
# projected contribution from input(s), hidden, and bias
proj4 = b + times(x, W) + times(dhs, H) + times(aux, A) if has_aux else \
b + times(x, W) + times(dhs, H)
it_proj = slice(proj4, stack_axis, 0 * stacked_dim,
1 * stacked_dim) # split along stack_axis
bit_proj = slice(proj4, stack_axis, 1 * stacked_dim, 2 * stacked_dim)
ft_proj = slice(proj4, stack_axis, 2 * stacked_dim, 3 * stacked_dim)
ot_proj = slice(proj4, stack_axis, 3 * stacked_dim, 4 * stacked_dim)
# add peephole connection if requested
def peep(x, c, C):
return x + C * c if use_peepholes else x
it = sigmoid(peep(it_proj, dcs, Ci)) # input gate(t)
bit = it * tanh(bit_proj) # applied to tanh of input network
ft = sigmoid(peep(ft_proj, dcs, Cf)) # forget-me-not gate(t)
bft = ft * dc # applied to cell(t-1)
ct = bft + bit # c(t) is sum of both
ot = sigmoid(peep(ot_proj, Sct(ct), Co)) # output gate(t)
ht = ot * tanh(ct) # applied to tanh(cell(t))
c = ct # cell value
h = times(Sht(ht), Wmr) if has_projection else \
ht
_name_node(h, 'h')
if _trace_layers:
_log_node(h) # this looks right
_name_node(c, 'c')
# TODO: figure out how to do scoping, and also rename all the apply... to expression
apply_x_h_c = combine([h, c])
# return to caller a helper function to create placeholders for recurrence
apply_x_h_c.create_placeholder = create_hc_placeholder
_name_and_extend_Function(apply_x_h_c, 'LSTM')
return apply_x_h_c
def __call__(self, *args):
return _apply(self, _as_tuple(args))
def _Infer(shape, axis):
return Record(shape=_as_tuple(shape),
axis=axis,
with_shape=lambda new_shape: _Infer(new_shape, axis))
