-
Notifications
You must be signed in to change notification settings - Fork 141
/
renormalization.py
238 lines (206 loc) · 11.9 KB
/
renormalization.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
# -*- coding: utf-8 -*-
from tensorflow.python.keras.engine.base_layer import Layer
from tensorflow.python.keras.engine.input_spec import InputSpec
from tensorflow.keras import initializers, regularizers
from tensorflow.keras import backend as K
from tensorflow.python.keras.utils.generic_utils import get_custom_objects
import numpy as np
class BatchRenormalization(Layer):
"""Batch renormalization layer (Sergey Ioffe, 2017). Source code original
link: https://github.com/titu1994/BatchRenormalization
Normalize the activations of the previous layer at each batch,
i.e. applies a transformation that maintains the mean activation
close to 0 and the activation standard deviation close to 1.
# Arguments
epsilon: small float > 0. Fuzz parameter.
Theano expects epsilon >= 1e-5.
mode: integer, 0, 1 or 2.
- 0: feature-wise normalization.
Each feature map in the input will
be normalized separately. The axis on which
to normalize is specified by the `axis` argument.
Note that if the input is a 4D image tensor
using Theano conventions (samples, channels, rows, cols)
then you should set `axis` to `1` to normalize along
the channels axis.
During training and testing we use running averages
computed during the training phase to normalize the data
- 1: sample-wise normalization. This mode assumes a 2D input.
- 2: feature-wise normalization, like mode 0, but
using per-batch statistics to normalize the data during both
testing and training.
axis: integer, axis along which to normalize in mode 0. For instance,
if your input tensor has shape (samples, channels, rows, cols),
set axis to 1 to normalize per feature map (channels axis).
momentum: momentum in the computation of the
exponential average of the mean and standard deviation
of the data, for feature-wise normalization.
r_max_value: Upper limit of the value of r_max.
d_max_value: Upper limit of the value of d_max.
t_delta: At each iteration, increment the value of t by t_delta.
weights: Initialization weights.
List of 2 Numpy arrays, with shapes:
`[(input_shape,), (input_shape,)]`
Note that the order of this list is [gamma, beta, mean, std]
beta_init: name of initialization function for shift parameter
(see [initializers](../initializers.md)), or alternatively,
Theano/TensorFlow function to use for weights initialization.
This parameter is only relevant if you don't pass a `weights` argument.
gamma_init: name of initialization function for scale parameter (see
[initializers](../initializers.md)), or alternatively,
Theano/TensorFlow function to use for weights initialization.
This parameter is only relevant if you don't pass a `weights` argument.
gamma_regularizer: instance of [WeightRegularizer](../regularizers.md)
(eg. L1 or L2 regularization), applied to the gamma vector.
beta_regularizer: instance of [WeightRegularizer](../regularizers.md),
applied to the beta vector.
# Input shape
Arbitrary. Use the keyword argument `input_shape`
(tuple of integers, does not include the samples axis)
when using this layer as the first layer in a model.
# Output shape
Same shape as input.
# References
- [Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift](https://arxiv.org/abs/1502.03167)
"""
def __init__(self, epsilon=1e-3, mode=0, axis=-1, momentum=0.99,
r_max_value=3., d_max_value=5., t_delta=1., weights=None, beta_init='zero',
gamma_init='one', gamma_regularizer=None, beta_regularizer=None,
**kwargs):
self.supports_masking = True
self.beta_init = initializers.get(beta_init)
self.gamma_init = initializers.get(gamma_init)
self.epsilon = epsilon
self.mode = mode
self.axis = axis
self.momentum = momentum
self.gamma_regularizer = regularizers.get(gamma_regularizer)
self.beta_regularizer = regularizers.get(beta_regularizer)
self.initial_weights = weights
self.r_max_value = r_max_value
self.d_max_value = d_max_value
self.t_delta = t_delta
if self.mode == 0:
self.uses_learning_phase = True
super(BatchRenormalization, self).__init__(**kwargs)
def build(self, input_shape):
self.input_spec = [InputSpec(shape=input_shape)]
shape = (input_shape[self.axis],)
self.gamma = self.add_weight(shape,
initializer=self.gamma_init,
regularizer=self.gamma_regularizer,
name='{}_gamma'.format(self.name))
self.beta = self.add_weight(shape,
initializer=self.beta_init,
regularizer=self.beta_regularizer,
name='{}_beta'.format(self.name))
self.running_mean = self.add_weight(shape, initializer='zero',
name='{}_running_mean'.format(self.name),
trainable=False)
# Note: running_std actually holds the running variance, not the running std.
self.running_std = self.add_weight(shape, initializer='one',
name='{}_running_std'.format(self.name),
trainable=False)
self.r_max = K.variable(np.ones((1,)), name='{}_r_max'.format(self.name))
self.d_max = K.variable(np.zeros((1,)), name='{}_d_max'.format(self.name))
self.t = K.variable(np.zeros((1,)), name='{}_t'.format(self.name))
if self.initial_weights is not None:
self.set_weights(self.initial_weights)
del self.initial_weights
self.built = True
def call(self, x, mask=None):
if self.mode == 0 or self.mode == 2:
assert self.built, 'Layer must be built before being called'
input_shape = K.int_shape(x)
reduction_axes = list(range(len(input_shape)))
del reduction_axes[self.axis]
broadcast_shape = [1] * len(input_shape)
broadcast_shape[self.axis] = input_shape[self.axis]
# mean_batch, var_batch = K.moments(x, reduction_axes, shift=None, keep_dims=False)
normed, mean_batch, var_batch = K.normalize_batch_in_training(
x, self.gamma, self.beta, reduction_axes,
epsilon=self.epsilon)
std_batch = (K.sqrt(var_batch + self.epsilon))
r_max_value = K.get_value(self.r_max)
r = std_batch / (K.sqrt(self.running_std + self.epsilon))
r = K.stop_gradient(K.clip(r, 1 / r_max_value, r_max_value))
d_max_value = K.get_value(self.d_max)
d = (mean_batch - self.running_mean) / K.sqrt(self.running_std + self.epsilon)
d = K.stop_gradient(K.clip(d, -d_max_value, d_max_value))
if sorted(reduction_axes) == range(K.ndim(x))[:-1]:
x_normed_batch = (x - mean_batch) / std_batch
x_normed = (x_normed_batch * r + d) * self.gamma + self.beta
else:
# need broadcasting
broadcast_mean = K.reshape(mean_batch, broadcast_shape)
broadcast_std = K.reshape(std_batch, broadcast_shape)
broadcast_r = K.reshape(r, broadcast_shape)
broadcast_d = K.reshape(d, broadcast_shape)
broadcast_beta = K.reshape(self.beta, broadcast_shape)
broadcast_gamma = K.reshape(self.gamma, broadcast_shape)
x_normed_batch = (x - broadcast_mean) / broadcast_std
x_normed = (x_normed_batch * broadcast_r + broadcast_d) * broadcast_gamma + broadcast_beta
# explicit update to moving mean and standard deviation
self.add_update([K.moving_average_update(self.running_mean, mean_batch, self.momentum),
K.moving_average_update(self.running_std, std_batch ** 2, self.momentum)], x)
# update r_max and d_max
t_val = K.get_value(self.t)
r_val = self.r_max_value / (1 + (self.r_max_value - 1) * np.exp(-t_val))
d_val = self.d_max_value / (1 + ((self.d_max_value / 1e-3) - 1) * np.exp(-(2 * t_val)))
t_val += float(self.t_delta)
self.add_update([K.update(self.r_max, r_val),
K.update(self.d_max, d_val),
K.update(self.t, t_val)], x)
if self.mode == 0:
if sorted(reduction_axes) == range(K.ndim(x))[:-1]:
x_normed_running = K.batch_normalization(
x, self.running_mean, self.running_std,
self.beta, self.gamma,
epsilon=self.epsilon)
else:
# need broadcasting
broadcast_running_mean = K.reshape(self.running_mean, broadcast_shape)
broadcast_running_std = K.reshape(self.running_std, broadcast_shape)
broadcast_beta = K.reshape(self.beta, broadcast_shape)
broadcast_gamma = K.reshape(self.gamma, broadcast_shape)
x_normed_running = K.batch_normalization(
x, broadcast_running_mean, broadcast_running_std,
broadcast_beta, broadcast_gamma,
epsilon=self.epsilon)
# pick the normalized form of x corresponding to the training phase
# for batch renormalization, inference time remains same as batchnorm
x_normed = K.in_train_phase(x_normed, x_normed_running)
elif self.mode == 1:
# sample-wise normalization
m = K.mean(x, axis=self.axis, keepdims=True)
std = K.sqrt(K.var(x, axis=self.axis, keepdims=True) + self.epsilon)
x_normed_batch = (x - m) / (std + self.epsilon)
r_max_value = K.get_value(self.r_max)
r = std / (self.running_std + self.epsilon)
r = K.stop_gradient(K.clip(r, 1 / r_max_value, r_max_value))
d_max_value = K.get_value(self.d_max)
d = (m - self.running_mean) / (self.running_std + self.epsilon)
d = K.stop_gradient(K.clip(d, -d_max_value, d_max_value))
x_normed = ((x_normed_batch * r) + d) * self.gamma + self.beta
# update r_max and d_max
t_val = K.get_value(self.t)
r_val = self.r_max_value / (1 + (self.r_max_value - 1) * np.exp(-t_val))
d_val = self.d_max_value / (1 + ((self.d_max_value / 1e-3) - 1) * np.exp(-(2 * t_val)))
t_val += float(self.t_delta)
self.add_update([K.update(self.r_max, r_val),
K.update(self.d_max, d_val),
K.update(self.t, t_val)], x)
return x_normed
def get_config(self):
config = {'epsilon': self.epsilon,
'mode': self.mode,
'axis': self.axis,
'gamma_regularizer': regularizers.serialize(self.gamma_regularizer),
'beta_regularizer': regularizers.serialize(self.beta_regularizer),
'momentum': self.momentum,
'r_max_value': self.r_max_value,
'd_max_value': self.d_max_value,
't_delta': self.t_delta}
base_config = super(BatchRenormalization, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
get_custom_objects().update({'BatchRenormalization': BatchRenormalization})