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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.
# ==============================================================================
"""Keras initializer classes (soon to be replaced with core TF initializers).
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import six
from tensorflow.python.keras.utils.generic_utils import deserialize_keras_object
from tensorflow.python.keras.utils.generic_utils import serialize_keras_object
from tensorflow.python.ops.init_ops import Constant
from tensorflow.python.ops.init_ops import Identity
from tensorflow.python.ops.init_ops import Initializer # pylint: disable=unused-import
from tensorflow.python.ops.init_ops import Ones
from tensorflow.python.ops.init_ops import Orthogonal
from tensorflow.python.ops.init_ops import RandomNormal
from tensorflow.python.ops.init_ops import RandomUniform
from tensorflow.python.ops.init_ops import TruncatedNormal
from tensorflow.python.ops.init_ops import VarianceScaling
from tensorflow.python.ops.init_ops import Zeros
from tensorflow.python.util.tf_export import tf_export
@tf_export('keras.initializers.lecun_normal')
def lecun_normal(seed=None):
"""LeCun normal initializer.
It draws samples from a truncated normal distribution centered on 0
with `stddev = sqrt(1 / fan_in)`
where `fan_in` is the number of input units in the weight tensor.
Arguments:
seed: A Python integer. Used to seed the random generator.
Returns:
An initializer.
References:
- [Self-Normalizing Neural Networks](https://arxiv.org/abs/1706.02515)
- [Efficient
Backprop](http://yann.lecun.com/exdb/publis/pdf/lecun-98b.pdf)
"""
return VarianceScaling(
scale=1., mode='fan_in', distribution='normal', seed=seed)
@tf_export('keras.initializers.lecun_uniform')
def lecun_uniform(seed=None):
"""LeCun uniform initializer.
It draws samples from a uniform distribution within [-limit, limit]
where `limit` is `sqrt(3 / fan_in)`
where `fan_in` is the number of input units in the weight tensor.
Arguments:
seed: A Python integer. Used to seed the random generator.
Returns:
An initializer.
References:
LeCun 98, Efficient Backprop,
http://yann.lecun.com/exdb/publis/pdf/lecun-98b.pdf
"""
return VarianceScaling(
scale=1., mode='fan_in', distribution='uniform', seed=seed)
@tf_export('keras.initializers.glorot_normal')
def glorot_normal(seed=None):
"""Glorot normal initializer, also called Xavier normal initializer.
It draws samples from a truncated normal distribution centered on 0
with `stddev = sqrt(2 / (fan_in + fan_out))`
where `fan_in` is the number of input units in the weight tensor
and `fan_out` is the number of output units in the weight tensor.
Arguments:
seed: A Python integer. Used to seed the random generator.
Returns:
An initializer.
References:
Glorot & Bengio, AISTATS 2010
http://jmlr.org/proceedings/papers/v9/glorot10a/glorot10a.pdf
"""
return VarianceScaling(
scale=1., mode='fan_avg', distribution='normal', seed=seed)
@tf_export('keras.initializers.glorot_uniform')
def glorot_uniform(seed=None):
"""Glorot uniform initializer, also called Xavier uniform initializer.
It draws samples from a uniform distribution within [-limit, limit]
where `limit` is `sqrt(6 / (fan_in + fan_out))`
where `fan_in` is the number of input units in the weight tensor
and `fan_out` is the number of output units in the weight tensor.
Arguments:
seed: A Python integer. Used to seed the random generator.
Returns:
An initializer.
References:
Glorot & Bengio, AISTATS 2010
http://jmlr.org/proceedings/papers/v9/glorot10a/glorot10a.pdf
"""
return VarianceScaling(
scale=1., mode='fan_avg', distribution='uniform', seed=seed)
@tf_export('keras.initializers.he_normal')
def he_normal(seed=None):
"""He normal initializer.
It draws samples from a truncated normal distribution centered on 0
with `stddev = sqrt(2 / fan_in)`
where `fan_in` is the number of input units in the weight tensor.
Arguments:
seed: A Python integer. Used to seed the random generator.
Returns:
An initializer.
References:
He et al., http://arxiv.org/abs/1502.01852
"""
return VarianceScaling(
scale=2., mode='fan_in', distribution='normal', seed=seed)
@tf_export('keras.initializers.he_uniform')
def he_uniform(seed=None):
"""He uniform variance scaling initializer.
It draws samples from a uniform distribution within [-limit, limit]
where `limit` is `sqrt(6 / fan_in)`
where `fan_in` is the number of input units in the weight tensor.
Arguments:
seed: A Python integer. Used to seed the random generator.
Returns:
An initializer.
References:
He et al., http://arxiv.org/abs/1502.01852
"""
return VarianceScaling(
scale=2., mode='fan_in', distribution='uniform', seed=seed)
# Compatibility aliases
# pylint: disable=invalid-name
zero = zeros = Zeros
one = ones = Ones
constant = Constant
uniform = random_uniform = RandomUniform
normal = random_normal = RandomNormal
truncated_normal = TruncatedNormal
identity = Identity
orthogonal = Orthogonal
# pylint: enable=invalid-name
# Utility functions
@tf_export('keras.initializers.serialize')
def serialize(initializer):
return serialize_keras_object(initializer)
@tf_export('keras.initializers.deserialize')
def deserialize(config, custom_objects=None):
return deserialize_keras_object(
config,
module_objects=globals(),
custom_objects=custom_objects,
printable_module_name='initializer')
@tf_export('keras.initializers.get')
def get(identifier):
if identifier is None:
return None
if isinstance(identifier, dict):
return deserialize(identifier)
elif isinstance(identifier, six.string_types):
config = {'class_name': str(identifier), 'config': {}}
return deserialize(config)
elif callable(identifier):
return identifier
else:
raise ValueError('Could not interpret initializer identifier: ' +
str(identifier))
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