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Add NASNet models

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Somshubra Majumdar
2017-11-16 22:27:47 -06:00
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keras_contrib/applications/__init__.py
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from .densenet import DenseNet
from .ror import ResidualOfResidual
from .resnet import ResNet, ResNet18, ResNet34, ResNet50, ResNet101, ResNet152
from .wide_resnet import WideResidualNetwork
from .nasnet import NASNet, NASNetLarge, NASNetMobile
keras_contrib/applications/nasnet.py
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"""NASNet (Neural Architecture Search Networks) for Keras
# References
- [Learning Transferable Architectures for Scalable Image Recognition]
(https://arxiv.org/abs/1707.07012)
Reference material for extended functionality:
- https://github.com/tensorflow/models/blob/master/research/slim/nets/
nasnet/nasnet.py
- https://github.com/taehoonlee/tensornets/blob/master/tensornets/nasnets.py
"""
from __future__ import print_function
from __future__ import absolute_import
from __future__ import division
import warnings
from keras.models import Model
from keras.layers import Input
from keras.layers import Activation
from keras.layers import Dense
from keras.layers import Dropout
from keras.layers import BatchNormalization
from keras.layers import MaxPooling2D
from keras.layers import AveragePooling2D
from keras.layers import GlobalAveragePooling2D
from keras.layers import GlobalMaxPooling2D
from keras.layers import Conv2D
from keras.layers import SeparableConv2D
from keras.layers import concatenate
from keras.layers import add
from keras.utils.data_utils import get_file
from keras.engine.topology import get_source_inputs
from keras.applications.imagenet_utils import _obtain_input_shape
from keras.applications.inception_v3 import preprocess_input
from keras.applications.imagenet_utils import decode_predictions
from keras import backend as K
_BN_DECAY = 0.9997
_BN_EPSILON = 1e-3
def NASNet(input_shape=None,
penultimate_filters=4032,
nb_blocks=6,
stem_filters=96,
skip_reduction=True,
use_auxilary_branch=False,
filters_multiplier=2,
dropout=0.5,
include_top=True,
weights='imagenet',
input_tensor=None,
pooling=None,
classes=1000,
default_size=None):
"""Instantiates a NASNet architecture.
Note that only TensorFlow is supported for now,
therefore it only works with the data format
`image_data_format='channels_last'` in your Keras config
at `~/.keras/keras.json`.
# Arguments
input_shape: optional shape tuple, only to be specified
if `include_top` is False (otherwise the input shape
has to be `(331, 331, 3)` for NASNetLarge or
`(224, 224, 3)` for NASNetMobile
It should have exactly 3 inputs channels,
and width and height should be no smaller than 32.
E.g. `(224, 224, 3)` would be one valid value.
penultimate_filters: number of filters in the penultimate layer.
NASNet models use the notation `NASNet (N @ P)`, where:
- N is the number of blocks
- P is the number of penultimate filters
nb_blocks: number of repeated blocks of the NASNet model.
NASNet models use the notation `NASNet (N @ P)`, where:
- N is the number of blocks
- P is the number of penultimate filters
stem_filters: number of filters in the initial stem block
skip_reduction: Whether to skip the reduction step at the tail
end of the network. Set to `False` for CIFAR models.
use_auxilary_branch: Whether to use the auxilary branch during
training or evaluation.
filters_multiplier: controls the width of the network.
- If `filters_multiplier` < 1.0, proportionally decreases the number
of filters in each layer.
- If `filters_multiplier` > 1.0, proportionally increases the number
of filters in each layer.
- If `filters_multiplier` = 1, default number of filters from the paper
are used at each layer.
dropout: dropout rate
include_top: whether to include the fully-connected
layer at the top of the network.
weights: `None` (random initialization) or
`imagenet` (ImageNet weights)
input_tensor: optional Keras tensor (i.e. output of
`layers.Input()`)
to use as image input for the model.
pooling: Optional pooling mode for feature extraction
when `include_top` is `False`.
- `None` means that the output of the model
will be the 4D tensor output of the
last convolutional layer.
- `avg` means that global average pooling
will be applied to the output of the
last convolutional layer, and thus
the output of the model will be a
2D tensor.
- `max` means that global max pooling will
be applied.
classes: optional number of classes to classify images
into, only to be specified if `include_top` is True, and
if no `weights` argument is specified.
default_size: specifies the default image size of the model
# Returns
A Keras model instance.
# Raises
ValueError: in case of invalid argument for `weights`,
or invalid input shape.
RuntimeError: If attempting to run this model with a
backend that does not support separable convolutions.
"""
if K.backend() != 'tensorflow':
raise RuntimeError('Only Tensorflow backend is currently supported, '
'as other backends do not support '
'separable convolution.')
if weights not in {'imagenet', None}:
raise ValueError('The `weights` argument should be either '
'`None` (random initialization) or `imagenet` '
'(pre-training on ImageNet).')
if weights == 'imagenet' and include_top and classes != 1000:
raise ValueError('If using `weights` as ImageNet with `include_top` '
'as true, `classes` should be 1000')
if default_size is None:
default_size = 331
# Determine proper input shape and default size.
input_shape = _obtain_input_shape(input_shape,
default_size=default_size,
min_size=32,
data_format=K.image_data_format(),
require_flatten=include_top or weights)
if K.image_data_format() != 'channels_last':
warnings.warn('The MobileNet family of models is only available '
'for the input data format "channels_last" '
'(width, height, channels). '
'However your settings specify the default '
'data format "channels_first" (channels, width, height).'
' You should set `image_data_format="channels_last"` '
'in your Keras config located at ~/.keras/keras.json. '
'The model being returned right now will expect inputs '
'to follow the "channels_last" data format.')
K.set_image_data_format('channels_last')
old_data_format = 'channels_first'
else:
old_data_format = None
if input_tensor is None:
img_input = Input(shape=input_shape)
else:
if not K.is_keras_tensor(input_tensor):
img_input = Input(tensor=input_tensor, shape=input_shape)
else:
img_input = input_tensor
assert penultimate_filters % ((2 ** nb_blocks) * 6), "`penultimate_filters` needs to be divisible " \
"by 6 * (2^N)."
filters = penultimate_filters // ((2 ** nb_blocks) * 6)
x = Conv2D(stem_filters, (3, 3), strides=(2, 2), padding='valid', use_bias=False, name='stem_conv1',
kernel_initializer='he_normal')(img_input)
x, p = _reduction_A(x, None, filters // (filters_multiplier ** 2), id='stem_1')
x, p = _reduction_A(x, p, filters // filters_multiplier, id='stem_2')
for i in range(nb_blocks):
x, p = _normal_A(x, p, filters, id='%d' % (i))
x, p0 = _reduction_A(x, p, filters * filters_multiplier, id='reduce_%d' % (nb_blocks))
p = p0 if not skip_reduction else p
for i in range(nb_blocks):
x, p = _normal_A(x, p, filters * filters_multiplier, id='%d' % (nb_blocks + i + 1))
auxilary_x = None
if use_auxilary_branch:
channel_dim = 1 if K.image_data_format() == 'channels_first' else -1
img_dim = 2 if K.image_data_format() == 'channels_first' else -2
auxilary_x = Activation('relu')(x)
auxilary_x = AveragePooling2D((5, 5), strides=(3, 3), padding='valid', name='aux_pool')(auxilary_x)
auxilary_x = Conv2D(128, (1, 1), padding='same', use_bias=False, name='aux_conv_projection',
kernel_initializer='he_normal')(auxilary_x)
auxilary_x = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name='aux_bn_projection')(auxilary_x)
auxilary_x = Activation('relu')(auxilary_x)
auxilary_x = Conv2D(768, auxilary_x._keras_shape[img_dim], padding='valid', use_bias=False,
kernel_initializer='he_normal', name='aux_conv_reduction')(auxilary_x)
auxilary_x = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name='aux_bn_reduction')(auxilary_x)
auxilary_x = Activation('relu')(auxilary_x)
auxilary_x = GlobalAveragePooling2D()(auxilary_x)
auxilary_x = Dense(classes, activation='softmax')(auxilary_x)
x, p0 = _reduction_A(x, p, filters * filters_multiplier ** 2, id='reduce_%d' % (2 * nb_blocks))
p = p0 if not skip_reduction else p
for i in range(nb_blocks):
x, p = _normal_A(x, p, filters * filters_multiplier ** 2, id='%d' % (2 * nb_blocks + i + 1))
x = Activation('relu')(x)
if include_top:
x = GlobalAveragePooling2D()(x)
x = Dropout(dropout)(x)
x = Dense(classes, activation='softmax')(x)
else:
if pooling == 'avg':
x = GlobalAveragePooling2D()(x)
elif pooling == 'max':
x = GlobalMaxPooling2D()(x)
# Ensure that the model takes into account
# any potential predecessors of `input_tensor`.
if input_tensor is not None:
inputs = get_source_inputs(input_tensor)
else:
inputs = img_input
# Create model.
if use_auxilary_branch:
model = Model(inputs, [x, auxilary_x], name='NASNet_with_auxilary')
else:
model = Model(inputs, x, name='NASNet')
# load weights (when available)
warnings.warn('Weights of NASNet models have not been ported yet for Keras.')
if old_data_format:
K.set_image_data_format(old_data_format)
return model
def NASNetLarge(input_shape=None,
dropout=0.5,
use_auxilary_branch=False,
include_top=True,
weights='imagenet',
input_tensor=None,
pooling=None,
classes=1000):
"""Instantiates a NASNet architecture in ImageNet mode.
Note that only TensorFlow is supported for now,
therefore it only works with the data format
`image_data_format='channels_last'` in your Keras config
at `~/.keras/keras.json`.
# Arguments
input_shape: optional shape tuple, only to be specified
if `include_top` is False (otherwise the input shape
has to be `(331, 331, 3)` for NASNetLarge.
It should have exactly 3 inputs channels,
and width and height should be no smaller than 32.
E.g. `(224, 224, 3)` would be one valid value.
use_auxilary_branch: Whether to use the auxilary branch during
training or evaluation.
dropout: dropout rate
include_top: whether to include the fully-connected
layer at the top of the network.
weights: `None` (random initialization) or
`imagenet` (ImageNet weights)
input_tensor: optional Keras tensor (i.e. output of
`layers.Input()`)
to use as image input for the model.
pooling: Optional pooling mode for feature extraction
when `include_top` is `False`.
- `None` means that the output of the model
will be the 4D tensor output of the
last convolutional layer.
- `avg` means that global average pooling
will be applied to the output of the
last convolutional layer, and thus
the output of the model will be a
2D tensor.
- `max` means that global max pooling will
be applied.
classes: optional number of classes to classify images
into, only to be specified if `include_top` is True, and
if no `weights` argument is specified.
default_size: specifies the default image size of the model
# Returns
A Keras model instance.
# Raises
ValueError: in case of invalid argument for `weights`,
or invalid input shape.
RuntimeError: If attempting to run this model with a
backend that does not support separable convolutions.
"""
return NASNet(input_shape,
penultimate_filters=4032,
nb_blocks=6,
stem_filters=96,
skip_reduction=True,
use_auxilary_branch=use_auxilary_branch,
filters_multiplier=2,
dropout=dropout,
include_top=include_top,
weights=weights,
input_tensor=input_tensor,
pooling=pooling,
classes=classes,
default_size=331)
def NASNetMobile(input_shape=None,
dropout=0.5,
use_auxilary_branch=False,
include_top=True,
weights='imagenet',
input_tensor=None,
pooling=None,
classes=1000):
"""Instantiates a NASNet architecture in CIFAR mode.
Note that only TensorFlow is supported for now,
therefore it only works with the data format
`image_data_format='channels_last'` in your Keras config
at `~/.keras/keras.json`.
# Arguments
input_shape: optional shape tuple, only to be specified
if `include_top` is False (otherwise the input shape
has to be `(224, 224, 3)` for NASNetMobile
It should have exactly 3 inputs channels,
and width and height should be no smaller than 32.
E.g. `(224, 224, 3)` would be one valid value.
use_auxilary_branch: Whether to use the auxilary branch during
training or evaluation.
dropout: dropout rate
include_top: whether to include the fully-connected
layer at the top of the network.
weights: `None` (random initialization) or
`imagenet` (ImageNet weights)
input_tensor: optional Keras tensor (i.e. output of
`layers.Input()`)
to use as image input for the model.
pooling: Optional pooling mode for feature extraction
when `include_top` is `False`.
- `None` means that the output of the model
will be the 4D tensor output of the
last convolutional layer.
- `avg` means that global average pooling
will be applied to the output of the
last convolutional layer, and thus
the output of the model will be a
2D tensor.
- `max` means that global max pooling will
be applied.
classes: optional number of classes to classify images
into, only to be specified if `include_top` is True, and
if no `weights` argument is specified.
default_size: specifies the default image size of the model
# Returns
A Keras model instance.
# Raises
ValueError: in case of invalid argument for `weights`,
or invalid input shape.
RuntimeError: If attempting to run this model with a
backend that does not support separable convolutions.
"""
return NASNet(input_shape,
penultimate_filters=1056,
nb_blocks=4,
stem_filters=32,
skip_reduction=False,
use_auxilary_branch=use_auxilary_branch,
filters_multiplier=2,
dropout=dropout,
include_top=include_top,
weights=weights,
input_tensor=input_tensor,
pooling=pooling,
classes=classes,
default_size=224)
def _separable_conv_block(ip, filters, kernel_size=(3, 3), strides=(1, 1), id=None):
'''Adds 2 blocks of [relu-separable conv-batchnorm]
# Arguments:
ip: input tensor
filters: number of output filters per layer
kernel_size: kernel size of separable convolutions
strides: strided convolution for downsampling
id: string id
# Returns:
a Keras tensor
'''
channel_dim = 1 if K.image_data_format() == 'channels_first' else -1
x = Activation('relu')(ip)
x = SeparableConv2D(filters, kernel_size, strides=strides, name='separable_conv_1_%s' % id,
padding='same', use_bias=False, kernel_initializer='he_normal')(x)
x = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name="separable_conv_1_bn_%s" % (id))(x)
x = Activation('relu')(x)
x = SeparableConv2D(filters, kernel_size, name='separable_conv_2_%s' % id,
padding='same', use_bias=False, kernel_initializer='he_normal')(x)
x = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name="separable_conv_2_bn_%s" % (id))(x)
return x
def _adjust_block(p, ip, filters, id=None):
'''
Adjusts the input `p` to match the shape of the `input`
or situations where the output number of filters needs to
be changed
# Arguments:
p: input tensor which needs to be modified
ip: input tensor whose shape needs to be matched
filters: number of output filters to be matched
id: string id
# Returns:
an adjusted Keras tensor
'''
channel_dim = 1 if K.image_data_format() == 'channels_first' else -1
img_dim = 2 if K.image_data_format() == 'channels_first' else -2
if p is None:
p = ip
elif p._keras_shape[img_dim] != ip._keras_shape[img_dim]:
p = Activation('relu', name='adjust_relu_1_%s' % id)(p)
p1 = AveragePooling2D((1, 1), strides=(2, 2), padding='valid', name='adjust_avg_pool_1_%s' % id)(p)
p1 = Conv2D(filters // 2, (1, 1), padding='same', use_bias=False,
name='adjust_conv_1_%s' % id, kernel_initializer='he_normal')(p1)
p2 = AveragePooling2D((1, 1), strides=(2, 2), padding='valid', name='adjust_avg_pool_2_%s' % id)(p)
p2 = Conv2D(filters // 2, (1, 1), padding='same', use_bias=False,
name='adjust_conv_2_%s' % id, kernel_initializer='he_normal')(p2)
p = concatenate([p1, p2], axis=channel_dim)
p = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name='adjust_bn_%s' % id)(p)
elif p._keras_shape[channel_dim] != filters:
p = Activation('relu')(p)
p = Conv2D(filters, (1, 1), strides=(1, 1), padding='same', name='adjust_conv_projection_%s' % id,
use_bias=False, kernel_initializer='he_normal')(p)
p = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name='adjust_bn_%s' % id)(p)
return p
def _normal_A(ip, p, filters, id=None):
'''Adds a Normal cell for NASNet-A (Fig. 4 in the paper)
# Arguments:
ip: input tensor `x`
p: input tensor `p`
filters: number of output filters
id: string id
# Returns:
a Keras tensor
'''
channel_dim = 1 if K.image_data_format() == 'channels_first' else -1
p = _adjust_block(p, ip, filters, id)
h = Activation('relu')(ip)
h = Conv2D(filters, (1, 1), strides=(1, 1), padding='same', name='normal_conv_1_%s' % id,
use_bias=False, kernel_initializer='he_normal')(h)
h = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name='normal_bn_1_%s' % id)(h)
x1 = _separable_conv_block(h, filters, id='normal_left1_%s' % id)
x1 = add([x1, h], name='normal_add_1_%s' % id)
x2_1 = _separable_conv_block(p, filters, id='normal_left2_%s' % id)
x2_2 = _separable_conv_block(h, filters, kernel_size=(5, 5), id='normal_right2_%s' % id)
x2 = add([x2_1, x2_2], name='normal_add_2_%s' % id)
x3 = AveragePooling2D((3, 3), strides=(1, 1), padding='same', name='normal_left3_%s' % (id))(h)
x3 = add([x3, p], name='normal_add_3_%s' % id)
x4_1 = AveragePooling2D((3, 3), strides=(1, 1), padding='same', name='normal_left4_%s' % (id))(p)
x4_2 = AveragePooling2D((3, 3), strides=(1, 1), padding='same', name='normal_right4_%s' % (id))(p)
x4 = add([x4_1, x4_2], name='normal_add_4_%s' % id)
x5_1 = _separable_conv_block(p, filters, (5, 5), id='normal_left5_%s' % id)
x5_2 = _separable_conv_block(p, filters, (3, 3), id='normal_right5_%s' % id)
x5 = add([x5_1, x5_2], name='normal_add_5_%s' % id)
x = concatenate([p, x2, x5, x3, x4, x1], axis=channel_dim, name='normal_concat_%s' % id)
return x, ip
def _reduction_A(ip, p, filters, id=None):
'''Adds a Reduction cell for NASNet-A (Fig. 4 in the paper)
# Arguments:
ip: input tensor `x`
p: input tensor `p`
filters: number of output filters
id: string id
# Returns:
a Keras tensor
'''
""""""
channel_dim = 1 if K.image_data_format() == 'channels_first' else -1
p = _adjust_block(p, ip, filters, id)
h = Activation('relu')(ip)
h = Conv2D(filters, (1, 1), strides=(1, 1), padding='same', name='reduction_conv_1_%s' % id,
use_bias=False, kernel_initializer='he_normal')(h)
h = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON,
name='reduction_bn_1_%s' % id)(h)
x1_1 = _separable_conv_block(p, filters, (7, 7), strides=(2, 2), id='reduction_left1_%s' % id)
x1_2 = _separable_conv_block(h, filters, (5, 5), strides=(2, 2), id='reduction_right1_%s' % id)
x1 = add([x1_1, x1_2], name='reduction_add_1_%s' % id)
x2_1 = MaxPooling2D((3, 3), strides=(2, 2), padding='same', name='reduction_left2_%s' % id)(h)
x2_2 = _separable_conv_block(p, filters, (7, 7), strides=(2, 2), id='reduction_right2_%s' % id)
x2 = add([x2_1, x2_2], name='reduction_add_2_%s' % id)
x3_1 = AveragePooling2D((3, 3), strides=(2, 2), padding='same', name='reduction_left3_%s' % id)(h)
x3_2 = _separable_conv_block(p, filters, (5, 5), strides=(2, 2), id='reduction_right3_%s' % id)
x3 = add([x3_1, x3_2], name='reduction_add3_%s' % id)
x4_1 = MaxPooling2D((3, 3), strides=(2, 2), padding='same', name='reduction_left4_%s' % id)(h)
x4_2 = _separable_conv_block(x1, filters, (3, 3), id='reduction_right4_%s' % id)
x4 = add([x4_1, x4_2], name='reduction_add4_%s' % id)
x5 = AveragePooling2D((3, 3), strides=(1, 1), padding='same', name='reduction_left5_%s' % id)(x1)
x = concatenate([x2, x3, x5, x4], axis=channel_dim, name='reduction_concat_%s' % id)
return x, ip