"""NASNet-A models for Keras NASNet refers to Neural Architecture Search Network, a family of models that were designed automatically by learning the model architectures directly on the dataset of interest. Here we consider NASNet-A, the highest performance model that was found for the CIFAR-10 dataset, and then extended to ImageNet 2012 dataset, obtaining state of the art performance on CIFAR-10 and ImageNet 2012. Only the NASNet-A models, and their respective weights, which are suited for ImageNet 2012 are provided. The below table describes the performance on ImageNet 2012: ------------------------------------------------------------------------------------ Architecture | Top-1 Acc | Top-5 Acc | Multiply-Adds | Params (M) ------------------------------------------------------------------------------------ | NASNet-A (4 @ 1056) | 74.0 % | 91.6 % | 564 M | 5.3 | | NASNet-A (6 @ 4032) | 82.7 % | 96.2 % | 23.8 B | 88.9 | ------------------------------------------------------------------------------------ Weights obtained from the official Tensorflow repository found at https://github.com/tensorflow/models/tree/master/research/slim/nets/nasnet # References: - [Learning Transferable Architectures for Scalable Image Recognition] (https://arxiv.org/abs/1707.07012) Based on the following implementations: - [TF Slim Implementation] (https://github.com/tensorflow/models/blob/master/research/slim/nets/nasnet/nasnet.) - [TensorNets implementation] (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 ZeroPadding2D from keras.layers import Cropping2D from keras.layers import concatenate from keras.layers import add from keras.regularizers import l2 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 NASNET_MOBILE_WEIGHT_PATH = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.0/NASNet-mobile.h5" NASNET_MOBILE_WEIGHT_PATH_NO_TOP = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.0/NASNet-mobile-no-top.h5" NASNET_MOBILE_WEIGHT_PATH_WITH_AUXULARY = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.0/NASNet-auxiliary-mobile.h5" NASNET_MOBILE_WEIGHT_PATH_WITH_AUXULARY_NO_TOP = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.0/NASNet-auxiliary-mobile-no-top.h5" NASNET_LARGE_WEIGHT_PATH = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.1/NASNet-large.h5" NASNET_LARGE_WEIGHT_PATH_NO_TOP = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.1/NASNet-large-no-top.h5" NASNET_LARGE_WEIGHT_PATH_WITH_auxiliary = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.1/NASNet-auxiliary-large.h5" NASNET_LARGE_WEIGHT_PATH_WITH_auxiliary_NO_TOP = "https://github.com/titu1994/Keras-NASNet/releases/download/v1.1/NASNet-auxiliary-large-no-top.h5" def NASNet(input_shape=None, penultimate_filters=4032, nb_blocks=6, stem_filters=96, skip_reduction=True, use_auxiliary_branch=False, filters_multiplier=2, dropout=0.5, weight_decay=5e-5, include_top=True, weights=None, 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_auxiliary_branch: Whether to use the auxiliary 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 weight_decay: l2 regularization weight 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, weights=weights) if K.image_data_format() != 'channels_last': warnings.warn('The NASNet 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 % 24 == 0, "`penultimate_filters` needs to be divisible " \ "by 24." channel_dim = 1 if K.image_data_format() == 'channels_first' else -1 filters = penultimate_filters // 24 if not skip_reduction: x = Conv2D(stem_filters, (3, 3), strides=(2, 2), padding='valid', use_bias=False, name='stem_conv1', kernel_initializer='he_normal', kernel_regularizer=l2(weight_decay))(img_input) else: x = Conv2D(stem_filters, (3, 3), strides=(1, 1), padding='same', use_bias=False, name='stem_conv1', kernel_initializer='he_normal', kernel_regularizer=l2(weight_decay))(img_input) x = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON, name='stem_bn1')(x) p = None if not skip_reduction: # imagenet / mobile mode x, p = _reduction_A(x, p, filters // (filters_multiplier ** 2), weight_decay, id='stem_1') x, p = _reduction_A(x, p, filters // filters_multiplier, weight_decay, id='stem_2') for i in range(nb_blocks): x, p = _normal_A(x, p, filters, weight_decay, id='%d' % (i)) x, p0 = _reduction_A(x, p, filters * filters_multiplier, weight_decay, 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, weight_decay, id='%d' % (nb_blocks + i + 1)) auxiliary_x = None if not skip_reduction: # imagenet / mobile mode if use_auxiliary_branch: auxiliary_x = _add_auxiliary_head(x, classes, weight_decay) x, p0 = _reduction_A(x, p, filters * filters_multiplier ** 2, weight_decay, id='reduce_%d' % (2 * nb_blocks)) if skip_reduction: # CIFAR mode if use_auxiliary_branch: auxiliary_x = _add_auxiliary_head(x, classes, weight_decay) p = p0 if not skip_reduction else p for i in range(nb_blocks): x, p = _normal_A(x, p, filters * filters_multiplier ** 2, weight_decay, 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', kernel_regularizer=l2(weight_decay), name='predictions')(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_auxiliary_branch: model = Model(inputs, [x, auxiliary_x], name='NASNet_with_auxiliary') else: model = Model(inputs, x, name='NASNet') # load weights if weights == 'imagenet': if default_size == 224: # mobile version if include_top: if use_auxiliary_branch: weight_path = NASNET_MOBILE_WEIGHT_PATH_WITH_AUXULARY model_name = 'nasnet_mobile_with_aux.h5' else: weight_path = NASNET_MOBILE_WEIGHT_PATH model_name = 'nasnet_mobile.h5' else: if use_auxiliary_branch: weight_path = NASNET_MOBILE_WEIGHT_PATH_WITH_AUXULARY_NO_TOP model_name = 'nasnet_mobile_with_aux_no_top.h5' else: weight_path = NASNET_MOBILE_WEIGHT_PATH_NO_TOP model_name = 'nasnet_mobile_no_top.h5' weights_file = get_file(model_name, weight_path, cache_subdir='models') model.load_weights(weights_file, by_name=True) elif default_size == 331: # large version if include_top: if use_auxiliary_branch: weight_path = NASNET_LARGE_WEIGHT_PATH_WITH_auxiliary model_name = 'nasnet_large_with_aux.h5' else: weight_path = NASNET_LARGE_WEIGHT_PATH model_name = 'nasnet_large.h5' else: if use_auxiliary_branch: weight_path = NASNET_LARGE_WEIGHT_PATH_WITH_auxiliary_NO_TOP model_name = 'nasnet_large_with_aux_no_top.h5' else: weight_path = NASNET_LARGE_WEIGHT_PATH_NO_TOP model_name = 'nasnet_large_no_top.h5' weights_file = get_file(model_name, weight_path, cache_subdir='models') model.load_weights(weights_file, by_name=True) else: raise ValueError('ImageNet weights can only be loaded on NASNetLarge or NASNetMobile') if old_data_format: K.set_image_data_format(old_data_format) return model def NASNetLarge(input_shape=(331, 331, 3), dropout=0.5, weight_decay=5e-5, use_auxiliary_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_auxiliary_branch: Whether to use the auxiliary branch during training or evaluation. dropout: dropout rate weight_decay: l2 regularization weight 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. """ global _BN_DECAY, _BN_EPSILON _BN_DECAY = 0.9997 _BN_EPSILON = 1e-3 return NASNet(input_shape, penultimate_filters=4032, nb_blocks=6, stem_filters=96, skip_reduction=False, use_auxiliary_branch=use_auxiliary_branch, filters_multiplier=2, dropout=dropout, weight_decay=weight_decay, include_top=include_top, weights=weights, input_tensor=input_tensor, pooling=pooling, classes=classes, default_size=331) def NASNetMobile(input_shape=(224, 224, 3), dropout=0.5, weight_decay=4e-5, use_auxiliary_branch=False, include_top=True, weights='imagenet', input_tensor=None, pooling=None, classes=1000): """Instantiates a NASNet architecture in Mobile 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 `(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_auxiliary_branch: Whether to use the auxiliary branch during training or evaluation. dropout: dropout rate weight_decay: l2 regularization weight 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. """ global _BN_DECAY, _BN_EPSILON _BN_DECAY = 0.9997 _BN_EPSILON = 1e-3 return NASNet(input_shape, penultimate_filters=1056, nb_blocks=4, stem_filters=32, skip_reduction=False, use_auxiliary_branch=use_auxiliary_branch, filters_multiplier=2, dropout=dropout, weight_decay=weight_decay, include_top=include_top, weights=weights, input_tensor=input_tensor, pooling=pooling, classes=classes, default_size=224) def NASNetCIFAR(input_shape=(32, 32, 3), dropout=0.0, weight_decay=5e-4, use_auxiliary_branch=False, include_top=True, weights=None, input_tensor=None, pooling=None, classes=10): """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 `(32, 32, 3)` for NASNetMobile It should have exactly 3 inputs channels, and width and height should be no smaller than 32. E.g. `(32, 32, 3)` would be one valid value. use_auxiliary_branch: Whether to use the auxiliary branch during training or evaluation. dropout: dropout rate weight_decay: l2 regularization weight 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. """ global _BN_DECAY, _BN_EPSILON _BN_DECAY = 0.9 _BN_EPSILON = 1e-5 return NASNet(input_shape, penultimate_filters=768, nb_blocks=6, stem_filters=32, skip_reduction=True, use_auxiliary_branch=use_auxiliary_branch, filters_multiplier=2, dropout=dropout, weight_decay=weight_decay, 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), weight_decay=5e-5, 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 weight_decay: l2 regularization weight id: string id # Returns: a Keras tensor ''' channel_dim = 1 if K.image_data_format() == 'channels_first' else -1 with K.name_scope('separable_conv_block_%s' % id): 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', kernel_regularizer=l2(weight_decay))(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', kernel_regularizer=l2(weight_decay))(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, weight_decay=5e-5, 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 weight_decay: l2 regularization weight 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 with K.name_scope('adjust_block'): if p is None: p = ip elif p._keras_shape[img_dim] != ip._keras_shape[img_dim]: with K.name_scope('adjust_reduction_block_%s' % id): 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, kernel_regularizer=l2(weight_decay), name='adjust_conv_1_%s' % id, kernel_initializer='he_normal')(p1) p2 = ZeroPadding2D(padding=((0, 1), (0, 1)))(p) p2 = Cropping2D(cropping=((1, 0), (1, 0)))(p2) p2 = AveragePooling2D((1, 1), strides=(2, 2), padding='valid', name='adjust_avg_pool_2_%s' % id)(p2) p2 = Conv2D(filters // 2, (1, 1), padding='same', use_bias=False, kernel_regularizer=l2(weight_decay), 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: with K.name_scope('adjust_projection_block_%s' % id): p = Activation('relu')(p) p = Conv2D(filters, (1, 1), strides=(1, 1), padding='same', name='adjust_conv_projection_%s' % id, use_bias=False, kernel_regularizer=l2(weight_decay), 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, weight_decay=5e-5, 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 weight_decay: l2 regularization weight id: string id # Returns: a Keras tensor ''' channel_dim = 1 if K.image_data_format() == 'channels_first' else -1 with K.name_scope('normal_A_block_%s' % id): p = _adjust_block(p, ip, filters, weight_decay, 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', kernel_regularizer=l2(weight_decay))(h) h = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON, name='normal_bn_1_%s' % id)(h) with K.name_scope('block_1'): x1_1 = _separable_conv_block(h, filters, kernel_size=(5, 5), weight_decay=weight_decay, id='normal_left1_%s' % id) x1_2 = _separable_conv_block(p, filters, weight_decay=weight_decay, id='normal_right1_%s' % id) x1 = add([x1_1, x1_2], name='normal_add_1_%s' % id) with K.name_scope('block_2'): x2_1 = _separable_conv_block(p, filters, (5, 5), weight_decay=weight_decay, id='normal_left2_%s' % id) x2_2 = _separable_conv_block(p, filters, (3, 3), weight_decay=weight_decay, id='normal_right2_%s' % id) x2 = add([x2_1, x2_2], name='normal_add_2_%s' % id) with K.name_scope('block_3'): 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) with K.name_scope('block_4'): 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) with K.name_scope('block_5'): x5 = _separable_conv_block(h, filters, weight_decay=weight_decay, id='normal_left5_%s' % id) x5 = add([x5, h], name='normal_add_5_%s' % id) x = concatenate([p, x1, x2, x3, x4, x5], axis=channel_dim, name='normal_concat_%s' % id) return x, ip def _reduction_A(ip, p, filters, weight_decay=5e-5, 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 weight_decay: l2 regularization weight id: string id # Returns: a Keras tensor ''' """""" channel_dim = 1 if K.image_data_format() == 'channels_first' else -1 with K.name_scope('reduction_A_block_%s' % id): p = _adjust_block(p, ip, filters, weight_decay, 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', kernel_regularizer=l2(weight_decay))(h) h = BatchNormalization(axis=channel_dim, momentum=_BN_DECAY, epsilon=_BN_EPSILON, name='reduction_bn_1_%s' % id)(h) with K.name_scope('block_1'): x1_1 = _separable_conv_block(h, filters, (5, 5), strides=(2, 2), weight_decay=weight_decay, id='reduction_left1_%s' % id) x1_2 = _separable_conv_block(p, filters, (7, 7), strides=(2, 2), weight_decay=weight_decay, id='reduction_1_%s' % id) x1 = add([x1_1, x1_2], name='reduction_add_1_%s' % id) with K.name_scope('block_2'): 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), weight_decay=weight_decay, id='reduction_right2_%s' % id) x2 = add([x2_1, x2_2], name='reduction_add_2_%s' % id) with K.name_scope('block_3'): 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), weight_decay=weight_decay, id='reduction_right3_%s' % id) x3 = add([x3_1, x3_2], name='reduction_add3_%s' % id) with K.name_scope('block_4'): x4 = AveragePooling2D((3, 3), strides=(1, 1), padding='same', name='reduction_left4_%s' % id)(x1) x4 = add([x2, x4]) with K.name_scope('block_5'): x5_1 = _separable_conv_block(x1, filters, (3, 3), weight_decay=weight_decay, id='reduction_left4_%s' % id) x5_2 = MaxPooling2D((3, 3), strides=(2, 2), padding='same', name='reduction_right5_%s' % id)(h) x5 = add([x5_1, x5_2], name='reduction_add4_%s' % id) x = concatenate([x2, x3, x4, x5], axis=channel_dim, name='reduction_concat_%s' % id) return x, ip def _add_auxiliary_head(x, classes, weight_decay): '''Adds an auxiliary head for training the model From section A.7 "Training of ImageNet models" of the paper, all NASNet models are trained using an auxiliary classifier around 2/3 of the depth of the network, with a loss weight of 0.4 # Arguments x: input tensor classes: number of output classes weight_decay: l2 regularization weight # Returns a keras Tensor ''' img_height = 1 if K.image_data_format() == 'channels_last' else 2 img_width = 2 if K.image_data_format() == 'channels_last' else 3 channel_axis = 1 if K.image_data_format() == 'channels_first' else -1 with K.name_scope('auxiliary_branch'): auxiliary_x = Activation('relu')(x) auxiliary_x = AveragePooling2D((5, 5), strides=(3, 3), padding='valid', name='aux_pool')(auxiliary_x) auxiliary_x = Conv2D(128, (1, 1), padding='same', use_bias=False, name='aux_conv_projection', kernel_initializer='he_normal', kernel_regularizer=l2(weight_decay))(auxiliary_x) auxiliary_x = BatchNormalization(axis=channel_axis, momentum=_BN_DECAY, epsilon=_BN_EPSILON, name='aux_bn_projection')(auxiliary_x) auxiliary_x = Activation('relu')(auxiliary_x) auxiliary_x = Conv2D(768, (auxiliary_x._keras_shape[img_height], auxiliary_x._keras_shape[img_width]), padding='valid', use_bias=False, kernel_initializer='he_normal', kernel_regularizer=l2(weight_decay), name='aux_conv_reduction')(auxiliary_x) auxiliary_x = BatchNormalization(axis=channel_axis, momentum=_BN_DECAY, epsilon=_BN_EPSILON, name='aux_bn_reduction')(auxiliary_x) auxiliary_x = Activation('relu')(auxiliary_x) auxiliary_x = GlobalAveragePooling2D()(auxiliary_x) auxiliary_x = Dense(classes, activation='softmax', kernel_regularizer=l2(weight_decay), name='aux_predictions')(auxiliary_x) return auxiliary_x if __name__ == '__main__': import tensorflow as tf sess = tf.Session() K.set_session(sess) model = NASNetLarge((331, 331, 3)) model.summary() writer = tf.summary.FileWriter('./logs/', graph=K.get_session().graph) writer.close()