"""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) (CVPR 2018) This model is based on the following implementations: - [TF Slim Implementation] (https://github.com/tensorflow/models/blob/master/research/slim/nets/nasnet/nasnet.py) - [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 os import warnings from . import correct_pad from . import get_submodules_from_kwargs from . import imagenet_utils from .imagenet_utils import decode_predictions from .imagenet_utils import _obtain_input_shape BASE_WEIGHTS_PATH = ('https://github.com/titu1994/Keras-NASNet/' 'releases/download/v1.2/') NASNET_MOBILE_WEIGHT_PATH = BASE_WEIGHTS_PATH + 'NASNet-mobile.h5' NASNET_MOBILE_WEIGHT_PATH_NO_TOP = BASE_WEIGHTS_PATH + 'NASNet-mobile-no-top.h5' NASNET_LARGE_WEIGHT_PATH = BASE_WEIGHTS_PATH + 'NASNet-large.h5' NASNET_LARGE_WEIGHT_PATH_NO_TOP = BASE_WEIGHTS_PATH + 'NASNet-large-no-top.h5' backend = None layers = None models = None keras_utils = None def NASNet(input_shape=None, penultimate_filters=4032, num_blocks=6, stem_block_filters=96, skip_reduction=True, filter_multiplier=2, include_top=True, weights=None, input_tensor=None, pooling=None, classes=1000, default_size=None, **kwargs): '''Instantiates a NASNet model. Optionally loads weights pre-trained on ImageNet. Note that the data format convention used by the model is the one specified in your Keras config at `~/.keras/keras.json`. # Arguments input_shape: Optional shape tuple, the input shape is by default `(331, 331, 3)` for NASNetLarge and `(224, 224, 3)` for NASNetMobile. It should have exactly 3 input 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 num_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_block_filters: Number of filters in the initial stem block skip_reduction: Whether to skip the reduction step at the tail end of the network. filter_multiplier: Controls the width of the network. - If `filter_multiplier` < 1.0, proportionally decreases the number of filters in each layer. - If `filter_multiplier` > 1.0, proportionally increases the number of filters in each layer. - If `filter_multiplier` = 1, default number of filters from the paper are used at each layer. 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 block. - `avg` means that global average pooling will be applied to the output of the last convolutional block, 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`, invalid input shape or invalid `penultimate_filters` value. ''' global backend, layers, models, keras_utils backend, layers, models, keras_utils = get_submodules_from_kwargs(kwargs) if not (weights in {'imagenet', None} or os.path.exists(weights)): raise ValueError('The `weights` argument should be either ' '`None` (random initialization), `imagenet` ' '(pre-training on ImageNet), ' 'or the path to the weights file to be loaded.') 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 (isinstance(input_shape, tuple) and None in input_shape and weights == 'imagenet'): raise ValueError('When specifying the input shape of a NASNet' ' and loading `ImageNet` weights, ' 'the input_shape argument must be static ' '(no None entries). Got: `input_shape=' + str(input_shape) + '`.') 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=backend.image_data_format(), require_flatten=True, weights=weights) if backend.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.') backend.set_image_data_format('channels_last') old_data_format = 'channels_first' else: old_data_format = None if input_tensor is None: img_input = layers.Input(shape=input_shape) else: if not backend.is_keras_tensor(input_tensor): img_input = layers.Input(tensor=input_tensor, shape=input_shape) else: img_input = input_tensor if penultimate_filters % (24 * (filter_multiplier ** 2)) != 0: raise ValueError( 'For NASNet-A models, the `penultimate_filters` must be a multiple ' 'of 24 * (`filter_multiplier` ** 2). Current value: %d' % penultimate_filters) channel_dim = 1 if backend.image_data_format() == 'channels_first' else -1 filters = penultimate_filters // 24 x = layers.Conv2D(stem_block_filters, (3, 3), strides=(2, 2), padding='valid', use_bias=False, name='stem_conv1', kernel_initializer='he_normal')(img_input) x = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='stem_bn1')(x) p = None x, p = _reduction_a_cell(x, p, filters // (filter_multiplier ** 2), block_id='stem_1') x, p = _reduction_a_cell(x, p, filters // filter_multiplier, block_id='stem_2') for i in range(num_blocks): x, p = _normal_a_cell(x, p, filters, block_id='%d' % (i)) x, p0 = _reduction_a_cell(x, p, filters * filter_multiplier, block_id='reduce_%d' % (num_blocks)) p = p0 if not skip_reduction else p for i in range(num_blocks): x, p = _normal_a_cell(x, p, filters * filter_multiplier, block_id='%d' % (num_blocks + i + 1)) x, p0 = _reduction_a_cell(x, p, filters * filter_multiplier ** 2, block_id='reduce_%d' % (2 * num_blocks)) p = p0 if not skip_reduction else p for i in range(num_blocks): x, p = _normal_a_cell(x, p, filters * filter_multiplier ** 2, block_id='%d' % (2 * num_blocks + i + 1)) x = layers.Activation('relu')(x) if include_top: x = layers.GlobalAveragePooling2D()(x) x = layers.Dense(classes, activation='softmax', name='predictions')(x) else: if pooling == 'avg': x = layers.GlobalAveragePooling2D()(x) elif pooling == 'max': x = layers.GlobalMaxPooling2D()(x) # Ensure that the model takes into account # any potential predecessors of `input_tensor`. if input_tensor is not None: inputs = keras_utils.get_source_inputs(input_tensor) else: inputs = img_input model = models.Model(inputs, x, name='NASNet') # Load weights. if weights == 'imagenet': if default_size == 224: # mobile version if include_top: weights_path = keras_utils.get_file( 'nasnet_mobile.h5', NASNET_MOBILE_WEIGHT_PATH, cache_subdir='models', file_hash='020fb642bf7360b370c678b08e0adf61') else: weights_path = keras_utils.get_file( 'nasnet_mobile_no_top.h5', NASNET_MOBILE_WEIGHT_PATH_NO_TOP, cache_subdir='models', file_hash='1ed92395b5b598bdda52abe5c0dbfd63') model.load_weights(weights_path) elif default_size == 331: # large version if include_top: weights_path = keras_utils.get_file( 'nasnet_large.h5', NASNET_LARGE_WEIGHT_PATH, cache_subdir='models', file_hash='11577c9a518f0070763c2b964a382f17') else: weights_path = keras_utils.get_file( 'nasnet_large_no_top.h5', NASNET_LARGE_WEIGHT_PATH_NO_TOP, cache_subdir='models', file_hash='d81d89dc07e6e56530c4e77faddd61b5') model.load_weights(weights_path) else: raise ValueError( 'ImageNet weights can only be loaded with NASNetLarge' ' or NASNetMobile') elif weights is not None: model.load_weights(weights) if old_data_format: backend.set_image_data_format(old_data_format) return model def NASNetLarge(input_shape=None, include_top=True, weights='imagenet', input_tensor=None, pooling=None, classes=1000, **kwargs): '''Instantiates a NASNet model in ImageNet mode. Optionally loads weights pre-trained on ImageNet. Note that the data format convention used by the model is the one specified 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. 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. # 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, num_blocks=6, stem_block_filters=96, skip_reduction=True, filter_multiplier=2, include_top=include_top, weights=weights, input_tensor=input_tensor, pooling=pooling, classes=classes, default_size=331, **kwargs) def NASNetMobile(input_shape=None, include_top=True, weights='imagenet', input_tensor=None, pooling=None, classes=1000, **kwargs): '''Instantiates a Mobile NASNet model in ImageNet mode. Optionally loads weights pre-trained on ImageNet. Note that the data format convention used by the model is the one specified 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. 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. # 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, num_blocks=4, stem_block_filters=32, skip_reduction=False, filter_multiplier=2, include_top=include_top, weights=weights, input_tensor=input_tensor, pooling=pooling, classes=classes, default_size=224, **kwargs) def _separable_conv_block(ip, filters, kernel_size=(3, 3), strides=(1, 1), block_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 block_id: String block_id # Returns A Keras tensor ''' channel_dim = 1 if backend.image_data_format() == 'channels_first' else -1 with backend.name_scope('separable_conv_block_%s' % block_id): x = layers.Activation('relu')(ip) if strides == (2, 2): x = layers.ZeroPadding2D( padding=correct_pad(backend, x, kernel_size), name='separable_conv_1_pad_%s' % block_id)(x) conv_pad = 'valid' else: conv_pad = 'same' x = layers.SeparableConv2D(filters, kernel_size, strides=strides, name='separable_conv_1_%s' % block_id, padding=conv_pad, use_bias=False, kernel_initializer='he_normal')(x) x = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='separable_conv_1_bn_%s' % (block_id))(x) x = layers.Activation('relu')(x) x = layers.SeparableConv2D(filters, kernel_size, name='separable_conv_2_%s' % block_id, padding='same', use_bias=False, kernel_initializer='he_normal')(x) x = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='separable_conv_2_bn_%s' % (block_id))(x) return x def _adjust_block(p, ip, filters, block_id=None): '''Adjusts the input `previous path` to match the shape of the `input`. Used in 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 block_id: String block_id # Returns Adjusted Keras tensor ''' channel_dim = 1 if backend.image_data_format() == 'channels_first' else -1 img_dim = 2 if backend.image_data_format() == 'channels_first' else -2 ip_shape = backend.int_shape(ip) if p is not None: p_shape = backend.int_shape(p) with backend.name_scope('adjust_block'): if p is None: p = ip elif p_shape[img_dim] != ip_shape[img_dim]: with backend.name_scope('adjust_reduction_block_%s' % block_id): p = layers.Activation('relu', name='adjust_relu_1_%s' % block_id)(p) p1 = layers.AveragePooling2D( (1, 1), strides=(2, 2), padding='valid', name='adjust_avg_pool_1_%s' % block_id)(p) p1 = layers.Conv2D( filters // 2, (1, 1), padding='same', use_bias=False, name='adjust_conv_1_%s' % block_id, kernel_initializer='he_normal')(p1) p2 = layers.ZeroPadding2D(padding=((0, 1), (0, 1)))(p) p2 = layers.Cropping2D(cropping=((1, 0), (1, 0)))(p2) p2 = layers.AveragePooling2D( (1, 1), strides=(2, 2), padding='valid', name='adjust_avg_pool_2_%s' % block_id)(p2) p2 = layers.Conv2D( filters // 2, (1, 1), padding='same', use_bias=False, name='adjust_conv_2_%s' % block_id, kernel_initializer='he_normal')(p2) p = layers.concatenate([p1, p2], axis=channel_dim) p = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='adjust_bn_%s' % block_id)(p) elif p_shape[channel_dim] != filters: with backend.name_scope('adjust_projection_block_%s' % block_id): p = layers.Activation('relu')(p) p = layers.Conv2D( filters, (1, 1), strides=(1, 1), padding='same', name='adjust_conv_projection_%s' % block_id, use_bias=False, kernel_initializer='he_normal')(p) p = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='adjust_bn_%s' % block_id)(p) return p def _normal_a_cell(ip, p, filters, block_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 block_id: String block_id # Returns A Keras tensor ''' channel_dim = 1 if backend.image_data_format() == 'channels_first' else -1 with backend.name_scope('normal_A_block_%s' % block_id): p = _adjust_block(p, ip, filters, block_id) h = layers.Activation('relu')(ip) h = layers.Conv2D( filters, (1, 1), strides=(1, 1), padding='same', name='normal_conv_1_%s' % block_id, use_bias=False, kernel_initializer='he_normal')(h) h = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='normal_bn_1_%s' % block_id)(h) with backend.name_scope('block_1'): x1_1 = _separable_conv_block( h, filters, kernel_size=(5, 5), block_id='normal_left1_%s' % block_id) x1_2 = _separable_conv_block( p, filters, block_id='normal_right1_%s' % block_id) x1 = layers.add([x1_1, x1_2], name='normal_add_1_%s' % block_id) with backend.name_scope('block_2'): x2_1 = _separable_conv_block( p, filters, (5, 5), block_id='normal_left2_%s' % block_id) x2_2 = _separable_conv_block( p, filters, (3, 3), block_id='normal_right2_%s' % block_id) x2 = layers.add([x2_1, x2_2], name='normal_add_2_%s' % block_id) with backend.name_scope('block_3'): x3 = layers.AveragePooling2D( (3, 3), strides=(1, 1), padding='same', name='normal_left3_%s' % (block_id))(h) x3 = layers.add([x3, p], name='normal_add_3_%s' % block_id) with backend.name_scope('block_4'): x4_1 = layers.AveragePooling2D( (3, 3), strides=(1, 1), padding='same', name='normal_left4_%s' % (block_id))(p) x4_2 = layers.AveragePooling2D( (3, 3), strides=(1, 1), padding='same', name='normal_right4_%s' % (block_id))(p) x4 = layers.add([x4_1, x4_2], name='normal_add_4_%s' % block_id) with backend.name_scope('block_5'): x5 = _separable_conv_block(h, filters, block_id='normal_left5_%s' % block_id) x5 = layers.add([x5, h], name='normal_add_5_%s' % block_id) x = layers.concatenate([p, x1, x2, x3, x4, x5], axis=channel_dim, name='normal_concat_%s' % block_id) return x, ip def _reduction_a_cell(ip, p, filters, block_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 block_id: String block_id # Returns A Keras tensor ''' channel_dim = 1 if backend.image_data_format() == 'channels_first' else -1 with backend.name_scope('reduction_A_block_%s' % block_id): p = _adjust_block(p, ip, filters, block_id) h = layers.Activation('relu')(ip) h = layers.Conv2D( filters, (1, 1), strides=(1, 1), padding='same', name='reduction_conv_1_%s' % block_id, use_bias=False, kernel_initializer='he_normal')(h) h = layers.BatchNormalization( axis=channel_dim, momentum=0.9997, epsilon=1e-3, name='reduction_bn_1_%s' % block_id)(h) h3 = layers.ZeroPadding2D( padding=correct_pad(backend, h, 3), name='reduction_pad_1_%s' % block_id)(h) with backend.name_scope('block_1'): x1_1 = _separable_conv_block( h, filters, (5, 5), strides=(2, 2), block_id='reduction_left1_%s' % block_id) x1_2 = _separable_conv_block( p, filters, (7, 7), strides=(2, 2), block_id='reduction_right1_%s' % block_id) x1 = layers.add([x1_1, x1_2], name='reduction_add_1_%s' % block_id) with backend.name_scope('block_2'): x2_1 = layers.MaxPooling2D( (3, 3), strides=(2, 2), padding='valid', name='reduction_left2_%s' % block_id)(h3) x2_2 = _separable_conv_block( p, filters, (7, 7), strides=(2, 2), block_id='reduction_right2_%s' % block_id) x2 = layers.add([x2_1, x2_2], name='reduction_add_2_%s' % block_id) with backend.name_scope('block_3'): x3_1 = layers.AveragePooling2D( (3, 3), strides=(2, 2), padding='valid', name='reduction_left3_%s' % block_id)(h3) x3_2 = _separable_conv_block( p, filters, (5, 5), strides=(2, 2), block_id='reduction_right3_%s' % block_id) x3 = layers.add([x3_1, x3_2], name='reduction_add3_%s' % block_id) with backend.name_scope('block_4'): x4 = layers.AveragePooling2D( (3, 3), strides=(1, 1), padding='same', name='reduction_left4_%s' % block_id)(x1) x4 = layers.add([x2, x4]) with backend.name_scope('block_5'): x5_1 = _separable_conv_block( x1, filters, (3, 3), block_id='reduction_left4_%s' % block_id) x5_2 = layers.MaxPooling2D( (3, 3), strides=(2, 2), padding='valid', name='reduction_right5_%s' % block_id)(h3) x5 = layers.add([x5_1, x5_2], name='reduction_add4_%s' % block_id) x = layers.concatenate( [x2, x3, x4, x5], axis=channel_dim, name='reduction_concat_%s' % block_id) return x, ip def preprocess_input(x, **kwargs): """Preprocesses a numpy array encoding a batch of images. # Arguments x: a 4D numpy array consists of RGB values within [0, 255]. # Returns Preprocessed array. """ return imagenet_utils.preprocess_input(x, mode='tf', **kwargs)