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# Copyright 2018 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.
# ==============================================================================
"""Builds the Wide-ResNet Model."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import custom_ops as ops
import numpy as np
import tensorflow as tf
def residual_block(
x, in_filter, out_filter, stride, activate_before_residual=False):
"""Adds residual connection to `x` in addition to applying BN->ReLU->3x3 Conv.
Args:
x: Tensor that is the output of the previous layer in the model.
in_filter: Number of filters `x` has.
out_filter: Number of filters that the output of this layer will have.
stride: Integer that specified what stride should be applied to `x`.
activate_before_residual: Boolean on whether a BN->ReLU should be applied
to x before the convolution is applied.
Returns:
A Tensor that is the result of applying two sequences of BN->ReLU->3x3 Conv
and then adding that Tensor to `x`.
"""
if activate_before_residual: # Pass up RELU and BN activation for resnet
with tf.variable_scope('shared_activation'):
x = ops.batch_norm(x, scope='init_bn')
x = tf.nn.relu(x)
orig_x = x
else:
orig_x = x
block_x = x
if not activate_before_residual:
with tf.variable_scope('residual_only_activation'):
block_x = ops.batch_norm(block_x, scope='init_bn')
block_x = tf.nn.relu(block_x)
with tf.variable_scope('sub1'):
block_x = ops.conv2d(
block_x, out_filter, 3, stride=stride, scope='conv1')
with tf.variable_scope('sub2'):
block_x = ops.batch_norm(block_x, scope='bn2')
block_x = tf.nn.relu(block_x)
block_x = ops.conv2d(
block_x, out_filter, 3, stride=1, scope='conv2')
with tf.variable_scope(
'sub_add'): # If number of filters do not agree then zero pad them
if in_filter != out_filter:
orig_x = ops.avg_pool(orig_x, stride, stride)
orig_x = ops.zero_pad(orig_x, in_filter, out_filter)
x = orig_x + block_x
return x
def _res_add(in_filter, out_filter, stride, x, orig_x):
"""Adds `x` with `orig_x`, both of which are layers in the model.
Args:
in_filter: Number of filters in `orig_x`.
out_filter: Number of filters in `x`.
stride: Integer specifying the stide that should be applied `orig_x`.
x: Tensor that is the output of the previous layer.
orig_x: Tensor that is the output of an earlier layer in the network.
Returns:
A Tensor that is the result of `x` and `orig_x` being added after
zero padding and striding are applied to `orig_x` to get the shapes
to match.
"""
if in_filter != out_filter:
orig_x = ops.avg_pool(orig_x, stride, stride)
orig_x = ops.zero_pad(orig_x, in_filter, out_filter)
x = x + orig_x
orig_x = x
return x, orig_x
def build_wrn_model(images, num_classes, wrn_size):
"""Builds the WRN model.
Build the Wide ResNet model from https://arxiv.org/abs/1605.07146.
Args:
images: Tensor of images that will be fed into the Wide ResNet Model.
num_classes: Number of classed that the model needs to predict.
wrn_size: Parameter that scales the number of filters in the Wide ResNet
model.
Returns:
The logits of the Wide ResNet model.
"""
kernel_size = wrn_size
filter_size = 3
num_blocks_per_resnet = 4
filters = [
min(kernel_size, 16), kernel_size, kernel_size * 2, kernel_size * 4
]
strides = [1, 2, 2] # stride for each resblock
# Run the first conv
with tf.variable_scope('init'):
x = images
output_filters = filters[0]
x = ops.conv2d(x, output_filters, filter_size, scope='init_conv')
first_x = x # Res from the beginning
orig_x = x # Res from previous block
for block_num in range(1, 4):
with tf.variable_scope('unit_{}_0'.format(block_num)):
activate_before_residual = True if block_num == 1 else False
x = residual_block(
x,
filters[block_num - 1],
filters[block_num],
strides[block_num - 1],
activate_before_residual=activate_before_residual)
for i in range(1, num_blocks_per_resnet):
with tf.variable_scope('unit_{}_{}'.format(block_num, i)):
x = residual_block(
x,
filters[block_num],
filters[block_num],
1,
activate_before_residual=False)
x, orig_x = _res_add(filters[block_num - 1], filters[block_num],
strides[block_num - 1], x, orig_x)
final_stride_val = np.prod(strides)
x, _ = _res_add(filters[0], filters[3], final_stride_val, x, first_x)
with tf.variable_scope('unit_last'):
x = ops.batch_norm(x, scope='final_bn')
x = tf.nn.relu(x)
x = ops.global_avg_pool(x)
logits = ops.fc(x, num_classes)
return logits
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