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# Copyright 2017 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.
# ==============================================================================
"""Contains the definition for the NASNet classification networks.
Paper: https://arxiv.org/abs/1707.07012
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import copy
import tensorflow as tf
from nets.nasnet import nasnet_utils
arg_scope = tf.contrib.framework.arg_scope
slim = tf.contrib.slim
# Notes for training NASNet Cifar Model
# -------------------------------------
# batch_size: 32
# learning rate: 0.025
# cosine (single period) learning rate decay
# auxiliary head loss weighting: 0.4
# clip global norm of all gradients by 5
def cifar_config():
return tf.contrib.training.HParams(
stem_multiplier=3.0,
drop_path_keep_prob=0.6,
num_cells=18,
use_aux_head=1,
num_conv_filters=32,
dense_dropout_keep_prob=1.0,
filter_scaling_rate=2.0,
num_reduction_layers=2,
data_format='NHWC',
skip_reduction_layer_input=0,
# 600 epochs with a batch size of 32
# This is used for the drop path probabilities since it needs to increase
# the drop out probability over the course of training.
total_training_steps=937500,
use_bounded_activation=False,
)
# Notes for training large NASNet model on ImageNet
# -------------------------------------
# batch size (per replica): 16
# learning rate: 0.015 * 100
# learning rate decay factor: 0.97
# num epochs per decay: 2.4
# sync sgd with 100 replicas
# auxiliary head loss weighting: 0.4
# label smoothing: 0.1
# clip global norm of all gradients by 10
def large_imagenet_config():
return tf.contrib.training.HParams(
stem_multiplier=3.0,
dense_dropout_keep_prob=0.5,
num_cells=18,
filter_scaling_rate=2.0,
num_conv_filters=168,
drop_path_keep_prob=0.7,
use_aux_head=1,
num_reduction_layers=2,
data_format='NHWC',
skip_reduction_layer_input=1,
total_training_steps=250000,
use_bounded_activation=False,
)
# Notes for training the mobile NASNet ImageNet model
# -------------------------------------
# batch size (per replica): 32
# learning rate: 0.04 * 50
# learning rate scaling factor: 0.97
# num epochs per decay: 2.4
# sync sgd with 50 replicas
# auxiliary head weighting: 0.4
# label smoothing: 0.1
# clip global norm of all gradients by 10
def mobile_imagenet_config():
return tf.contrib.training.HParams(
stem_multiplier=1.0,
dense_dropout_keep_prob=0.5,
num_cells=12,
filter_scaling_rate=2.0,
drop_path_keep_prob=1.0,
num_conv_filters=44,
use_aux_head=1,
num_reduction_layers=2,
data_format='NHWC',
skip_reduction_layer_input=0,
total_training_steps=250000,
use_bounded_activation=False,
)
def _update_hparams(hparams, is_training):
"""Update hparams for given is_training option."""
if not is_training:
hparams.set_hparam('drop_path_keep_prob', 1.0)
def nasnet_cifar_arg_scope(weight_decay=5e-4,
batch_norm_decay=0.9,
batch_norm_epsilon=1e-5):
"""Defines the default arg scope for the NASNet-A Cifar model.
Args:
weight_decay: The weight decay to use for regularizing the model.
batch_norm_decay: Decay for batch norm moving average.
batch_norm_epsilon: Small float added to variance to avoid dividing by zero
in batch norm.
Returns:
An `arg_scope` to use for the NASNet Cifar Model.
"""
batch_norm_params = {
# Decay for the moving averages.
'decay': batch_norm_decay,
# epsilon to prevent 0s in variance.
'epsilon': batch_norm_epsilon,
'scale': True,
'fused': True,
}
weights_regularizer = tf.contrib.layers.l2_regularizer(weight_decay)
weights_initializer = tf.contrib.layers.variance_scaling_initializer(
mode='FAN_OUT')
with arg_scope([slim.fully_connected, slim.conv2d, slim.separable_conv2d],
weights_regularizer=weights_regularizer,
weights_initializer=weights_initializer):
with arg_scope([slim.fully_connected],
activation_fn=None, scope='FC'):
with arg_scope([slim.conv2d, slim.separable_conv2d],
activation_fn=None, biases_initializer=None):
with arg_scope([slim.batch_norm], **batch_norm_params) as sc:
return sc
def nasnet_mobile_arg_scope(weight_decay=4e-5,
batch_norm_decay=0.9997,
batch_norm_epsilon=1e-3):
"""Defines the default arg scope for the NASNet-A Mobile ImageNet model.
Args:
weight_decay: The weight decay to use for regularizing the model.
batch_norm_decay: Decay for batch norm moving average.
batch_norm_epsilon: Small float added to variance to avoid dividing by zero
in batch norm.
Returns:
An `arg_scope` to use for the NASNet Mobile Model.
"""
batch_norm_params = {
# Decay for the moving averages.
'decay': batch_norm_decay,
# epsilon to prevent 0s in variance.
'epsilon': batch_norm_epsilon,
'scale': True,
'fused': True,
}
weights_regularizer = tf.contrib.layers.l2_regularizer(weight_decay)
weights_initializer = tf.contrib.layers.variance_scaling_initializer(
mode='FAN_OUT')
with arg_scope([slim.fully_connected, slim.conv2d, slim.separable_conv2d],
weights_regularizer=weights_regularizer,
weights_initializer=weights_initializer):
with arg_scope([slim.fully_connected],
activation_fn=None, scope='FC'):
with arg_scope([slim.conv2d, slim.separable_conv2d],
activation_fn=None, biases_initializer=None):
with arg_scope([slim.batch_norm], **batch_norm_params) as sc:
return sc
def nasnet_large_arg_scope(weight_decay=5e-5,
batch_norm_decay=0.9997,
batch_norm_epsilon=1e-3):
"""Defines the default arg scope for the NASNet-A Large ImageNet model.
Args:
weight_decay: The weight decay to use for regularizing the model.
batch_norm_decay: Decay for batch norm moving average.
batch_norm_epsilon: Small float added to variance to avoid dividing by zero
in batch norm.
Returns:
An `arg_scope` to use for the NASNet Large Model.
"""
batch_norm_params = {
# Decay for the moving averages.
'decay': batch_norm_decay,
# epsilon to prevent 0s in variance.
'epsilon': batch_norm_epsilon,
'scale': True,
'fused': True,
}
weights_regularizer = tf.contrib.layers.l2_regularizer(weight_decay)
weights_initializer = tf.contrib.layers.variance_scaling_initializer(
mode='FAN_OUT')
with arg_scope([slim.fully_connected, slim.conv2d, slim.separable_conv2d],
weights_regularizer=weights_regularizer,
weights_initializer=weights_initializer):
with arg_scope([slim.fully_connected],
activation_fn=None, scope='FC'):
with arg_scope([slim.conv2d, slim.separable_conv2d],
activation_fn=None, biases_initializer=None):
with arg_scope([slim.batch_norm], **batch_norm_params) as sc:
return sc
def _build_aux_head(net, end_points, num_classes, hparams, scope):
"""Auxiliary head used for all models across all datasets."""
activation_fn = tf.nn.relu6 if hparams.use_bounded_activation else tf.nn.relu
with tf.variable_scope(scope):
aux_logits = tf.identity(net)
with tf.variable_scope('aux_logits'):
aux_logits = slim.avg_pool2d(
aux_logits, [5, 5], stride=3, padding='VALID')
aux_logits = slim.conv2d(aux_logits, 128, [1, 1], scope='proj')
aux_logits = slim.batch_norm(aux_logits, scope='aux_bn0')
aux_logits = activation_fn(aux_logits)
# Shape of feature map before the final layer.
shape = aux_logits.shape
if hparams.data_format == 'NHWC':
shape = shape[1:3]
else:
shape = shape[2:4]
aux_logits = slim.conv2d(aux_logits, 768, shape, padding='VALID')
aux_logits = slim.batch_norm(aux_logits, scope='aux_bn1')
aux_logits = activation_fn(aux_logits)
aux_logits = tf.contrib.layers.flatten(aux_logits)
aux_logits = slim.fully_connected(aux_logits, num_classes)
end_points['AuxLogits'] = aux_logits
def _imagenet_stem(inputs, hparams, stem_cell, current_step=None):
"""Stem used for models trained on ImageNet."""
num_stem_cells = 2
# 149 x 149 x 32
num_stem_filters = int(32 * hparams.stem_multiplier)
net = slim.conv2d(
inputs, num_stem_filters, [3, 3], stride=2, scope='conv0',
padding='VALID')
net = slim.batch_norm(net, scope='conv0_bn')
# Run the reduction cells
cell_outputs = [None, net]
filter_scaling = 1.0 / (hparams.filter_scaling_rate**num_stem_cells)
for cell_num in range(num_stem_cells):
net = stem_cell(
net,
scope='cell_stem_{}'.format(cell_num),
filter_scaling=filter_scaling,
stride=2,
prev_layer=cell_outputs[-2],
cell_num=cell_num,
current_step=current_step)
cell_outputs.append(net)
filter_scaling *= hparams.filter_scaling_rate
return net, cell_outputs
def _cifar_stem(inputs, hparams):
"""Stem used for models trained on Cifar."""
num_stem_filters = int(hparams.num_conv_filters * hparams.stem_multiplier)
net = slim.conv2d(
inputs,
num_stem_filters,
3,
scope='l1_stem_3x3')
net = slim.batch_norm(net, scope='l1_stem_bn')
return net, [None, net]
def build_nasnet_cifar(images, num_classes,
is_training=True,
config=None,
current_step=None):
"""Build NASNet model for the Cifar Dataset."""
hparams = cifar_config() if config is None else copy.deepcopy(config)
_update_hparams(hparams, is_training)
if tf.test.is_gpu_available() and hparams.data_format == 'NHWC':
tf.logging.info('A GPU is available on the machine, consider using NCHW '
'data format for increased speed on GPU.')
if hparams.data_format == 'NCHW':
images = tf.transpose(images, [0, 3, 1, 2])
# Calculate the total number of cells in the network
# Add 2 for the reduction cells
total_num_cells = hparams.num_cells + 2
normal_cell = nasnet_utils.NasNetANormalCell(
hparams.num_conv_filters, hparams.drop_path_keep_prob,
total_num_cells, hparams.total_training_steps,
hparams.use_bounded_activation)
reduction_cell = nasnet_utils.NasNetAReductionCell(
hparams.num_conv_filters, hparams.drop_path_keep_prob,
total_num_cells, hparams.total_training_steps,
hparams.use_bounded_activation)
with arg_scope([slim.dropout, nasnet_utils.drop_path, slim.batch_norm],
is_training=is_training):
with arg_scope([slim.avg_pool2d,
slim.max_pool2d,
slim.conv2d,
slim.batch_norm,
slim.separable_conv2d,
nasnet_utils.factorized_reduction,
nasnet_utils.global_avg_pool,
nasnet_utils.get_channel_index,
nasnet_utils.get_channel_dim],
data_format=hparams.data_format):
return _build_nasnet_base(images,
normal_cell=normal_cell,
reduction_cell=reduction_cell,
num_classes=num_classes,
hparams=hparams,
is_training=is_training,
stem_type='cifar',
current_step=current_step)
build_nasnet_cifar.default_image_size = 32
def build_nasnet_mobile(images, num_classes,
is_training=True,
final_endpoint=None,
config=None,
current_step=None):
"""Build NASNet Mobile model for the ImageNet Dataset."""
hparams = (mobile_imagenet_config() if config is None
else copy.deepcopy(config))
_update_hparams(hparams, is_training)
if tf.test.is_gpu_available() and hparams.data_format == 'NHWC':
tf.logging.info('A GPU is available on the machine, consider using NCHW '
'data format for increased speed on GPU.')
if hparams.data_format == 'NCHW':
images = tf.transpose(images, [0, 3, 1, 2])
# Calculate the total number of cells in the network
# Add 2 for the reduction cells
total_num_cells = hparams.num_cells + 2
# If ImageNet, then add an additional two for the stem cells
total_num_cells += 2
normal_cell = nasnet_utils.NasNetANormalCell(
hparams.num_conv_filters, hparams.drop_path_keep_prob,
total_num_cells, hparams.total_training_steps,
hparams.use_bounded_activation)
reduction_cell = nasnet_utils.NasNetAReductionCell(
hparams.num_conv_filters, hparams.drop_path_keep_prob,
total_num_cells, hparams.total_training_steps,
hparams.use_bounded_activation)
with arg_scope([slim.dropout, nasnet_utils.drop_path, slim.batch_norm],
is_training=is_training):
with arg_scope([slim.avg_pool2d,
slim.max_pool2d,
slim.conv2d,
slim.batch_norm,
slim.separable_conv2d,
nasnet_utils.factorized_reduction,
nasnet_utils.global_avg_pool,
nasnet_utils.get_channel_index,
nasnet_utils.get_channel_dim],
data_format=hparams.data_format):
return _build_nasnet_base(images,
normal_cell=normal_cell,
reduction_cell=reduction_cell,
num_classes=num_classes,
hparams=hparams,
is_training=is_training,
stem_type='imagenet',
final_endpoint=final_endpoint,
current_step=current_step)
build_nasnet_mobile.default_image_size = 224
def build_nasnet_large(images, num_classes,
is_training=True,
final_endpoint=None,
config=None,
current_step=None):
"""Build NASNet Large model for the ImageNet Dataset."""
hparams = (large_imagenet_config() if config is None
else copy.deepcopy(config))
_update_hparams(hparams, is_training)
if tf.test.is_gpu_available() and hparams.data_format == 'NHWC':
tf.logging.info('A GPU is available on the machine, consider using NCHW '
'data format for increased speed on GPU.')
if hparams.data_format == 'NCHW':
images = tf.transpose(images, [0, 3, 1, 2])
# Calculate the total number of cells in the network
# Add 2 for the reduction cells
total_num_cells = hparams.num_cells + 2
# If ImageNet, then add an additional two for the stem cells
total_num_cells += 2
normal_cell = nasnet_utils.NasNetANormalCell(
hparams.num_conv_filters, hparams.drop_path_keep_prob,
total_num_cells, hparams.total_training_steps,
hparams.use_bounded_activation)
reduction_cell = nasnet_utils.NasNetAReductionCell(
hparams.num_conv_filters, hparams.drop_path_keep_prob,
total_num_cells, hparams.total_training_steps,
hparams.use_bounded_activation)
with arg_scope([slim.dropout, nasnet_utils.drop_path, slim.batch_norm],
is_training=is_training):
with arg_scope([slim.avg_pool2d,
slim.max_pool2d,
slim.conv2d,
slim.batch_norm,
slim.separable_conv2d,
nasnet_utils.factorized_reduction,
nasnet_utils.global_avg_pool,
nasnet_utils.get_channel_index,
nasnet_utils.get_channel_dim],
data_format=hparams.data_format):
return _build_nasnet_base(images,
normal_cell=normal_cell,
reduction_cell=reduction_cell,
num_classes=num_classes,
hparams=hparams,
is_training=is_training,
stem_type='imagenet',
final_endpoint=final_endpoint,
current_step=current_step)
build_nasnet_large.default_image_size = 331
def _build_nasnet_base(images,
normal_cell,
reduction_cell,
num_classes,
hparams,
is_training,
stem_type,
final_endpoint=None,
current_step=None):
"""Constructs a NASNet image model."""
end_points = {}
def add_and_check_endpoint(endpoint_name, net):
end_points[endpoint_name] = net
return final_endpoint and (endpoint_name == final_endpoint)
# Find where to place the reduction cells or stride normal cells
reduction_indices = nasnet_utils.calc_reduction_layers(
hparams.num_cells, hparams.num_reduction_layers)
stem_cell = reduction_cell
if stem_type == 'imagenet':
stem = lambda: _imagenet_stem(images, hparams, stem_cell)
elif stem_type == 'cifar':
stem = lambda: _cifar_stem(images, hparams)
else:
raise ValueError('Unknown stem_type: ', stem_type)
net, cell_outputs = stem()
if add_and_check_endpoint('Stem', net): return net, end_points
# Setup for building in the auxiliary head.
aux_head_cell_idxes = []
if len(reduction_indices) >= 2:
aux_head_cell_idxes.append(reduction_indices[1] - 1)
# Run the cells
filter_scaling = 1.0
# true_cell_num accounts for the stem cells
true_cell_num = 2 if stem_type == 'imagenet' else 0
activation_fn = tf.nn.relu6 if hparams.use_bounded_activation else tf.nn.relu
for cell_num in range(hparams.num_cells):
stride = 1
if hparams.skip_reduction_layer_input:
prev_layer = cell_outputs[-2]
if cell_num in reduction_indices:
filter_scaling *= hparams.filter_scaling_rate
net = reduction_cell(
net,
scope='reduction_cell_{}'.format(reduction_indices.index(cell_num)),
filter_scaling=filter_scaling,
stride=2,
prev_layer=cell_outputs[-2],
cell_num=true_cell_num,
current_step=current_step)
if add_and_check_endpoint(
'Reduction_Cell_{}'.format(reduction_indices.index(cell_num)), net):
return net, end_points
true_cell_num += 1
cell_outputs.append(net)
if not hparams.skip_reduction_layer_input:
prev_layer = cell_outputs[-2]
net = normal_cell(
net,
scope='cell_{}'.format(cell_num),
filter_scaling=filter_scaling,
stride=stride,
prev_layer=prev_layer,
cell_num=true_cell_num,
current_step=current_step)
if add_and_check_endpoint('Cell_{}'.format(cell_num), net):
return net, end_points
true_cell_num += 1
if (hparams.use_aux_head and cell_num in aux_head_cell_idxes and
num_classes and is_training):
aux_net = activation_fn(net)
_build_aux_head(aux_net, end_points, num_classes, hparams,
scope='aux_{}'.format(cell_num))
cell_outputs.append(net)
# Final softmax layer
with tf.variable_scope('final_layer'):
net = activation_fn(net)
net = nasnet_utils.global_avg_pool(net)
if add_and_check_endpoint('global_pool', net) or not num_classes:
return net, end_points
net = slim.dropout(net, hparams.dense_dropout_keep_prob, scope='dropout')
logits = slim.fully_connected(net, num_classes)
if add_and_check_endpoint('Logits', logits):
return net, end_points
predictions = tf.nn.softmax(logits, name='predictions')
if add_and_check_endpoint('Predictions', predictions):
return net, end_points
return logits, end_points
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