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# Copyright 2015 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Layers that operate regularization via the addition of noise.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import numpy as np
from tensorflow.python.keras import backend as K
from tensorflow.python.keras.engine.base_layer import Layer
from tensorflow.python.keras.utils import tf_utils
from tensorflow.python.ops import array_ops
from tensorflow.python.ops import math_ops
from tensorflow.python.util.tf_export import tf_export
@tf_export('keras.layers.GaussianNoise')
class GaussianNoise(Layer):
"""Apply additive zero-centered Gaussian noise.
This is useful to mitigate overfitting
(you could see it as a form of random data augmentation).
Gaussian Noise (GS) is a natural choice as corruption process
for real valued inputs.
As it is a regularization layer, it is only active at training time.
Arguments:
stddev: float, standard deviation of the noise distribution.
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.
"""
def __init__(self, stddev, **kwargs):
super(GaussianNoise, self).__init__(**kwargs)
self.supports_masking = True
self.stddev = stddev
def call(self, inputs, training=None):
def noised():
return inputs + K.random_normal(
shape=array_ops.shape(inputs), mean=0., stddev=self.stddev)
return K.in_train_phase(noised, inputs, training=training)
def get_config(self):
config = {'stddev': self.stddev}
base_config = super(GaussianNoise, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
@tf_utils.shape_type_conversion
def compute_output_shape(self, input_shape):
return input_shape
@tf_export('keras.layers.GaussianDropout')
class GaussianDropout(Layer):
"""Apply multiplicative 1-centered Gaussian noise.
As it is a regularization layer, it is only active at training time.
Arguments:
rate: float, drop probability (as with `Dropout`).
The multiplicative noise will have
standard deviation `sqrt(rate / (1 - rate))`.
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.
"""
def __init__(self, rate, **kwargs):
super(GaussianDropout, self).__init__(**kwargs)
self.supports_masking = True
self.rate = rate
def call(self, inputs, training=None):
if 0 < self.rate < 1:
def noised():
stddev = np.sqrt(self.rate / (1.0 - self.rate))
return inputs * K.random_normal(
shape=array_ops.shape(inputs), mean=1.0, stddev=stddev)
return K.in_train_phase(noised, inputs, training=training)
return inputs
def get_config(self):
config = {'rate': self.rate}
base_config = super(GaussianDropout, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
@tf_utils.shape_type_conversion
def compute_output_shape(self, input_shape):
return input_shape
@tf_export('keras.layers.AlphaDropout')
class AlphaDropout(Layer):
"""Applies Alpha Dropout to the input.
Alpha Dropout is a `Dropout` that keeps mean and variance of inputs
to their original values, in order to ensure the self-normalizing property
even after this dropout.
Alpha Dropout fits well to Scaled Exponential Linear Units
by randomly setting activations to the negative saturation value.
Arguments:
rate: float, drop probability (as with `Dropout`).
The multiplicative noise will have
standard deviation `sqrt(rate / (1 - rate))`.
seed: A Python integer to use as random seed.
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.
"""
def __init__(self, rate, noise_shape=None, seed=None, **kwargs):
super(AlphaDropout, self).__init__(**kwargs)
self.rate = rate
self.noise_shape = noise_shape
self.seed = seed
self.supports_masking = True
def _get_noise_shape(self, inputs):
return self.noise_shape if self.noise_shape else array_ops.shape(inputs)
def call(self, inputs, training=None):
if 0. < self.rate < 1.:
noise_shape = self._get_noise_shape(inputs)
def dropped_inputs(inputs=inputs, rate=self.rate, seed=self.seed): # pylint: disable=missing-docstring
alpha = 1.6732632423543772848170429916717
scale = 1.0507009873554804934193349852946
alpha_p = -alpha * scale
kept_idx = math_ops.greater_equal(
K.random_uniform(noise_shape, seed=seed), rate)
kept_idx = math_ops.cast(kept_idx, K.floatx())
# Get affine transformation params
a = ((1 - rate) * (1 + rate * alpha_p**2))**-0.5
b = -a * alpha_p * rate
# Apply mask
x = inputs * kept_idx + alpha_p * (1 - kept_idx)
# Do affine transformation
return a * x + b
return K.in_train_phase(dropped_inputs, inputs, training=training)
return inputs
def get_config(self):
config = {'rate': self.rate}
base_config = super(AlphaDropout, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
@tf_utils.shape_type_conversion
def compute_output_shape(self, input_shape):
return input_shape
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