def init_model(backbone_model_name,
freeze_backbone_for_N_epochs,
input_shape,
region_num,
attribute_name_to_label_encoder_dict,
kernel_regularization_factor,
bias_regularization_factor,
gamma_regularization_factor,
beta_regularization_factor,
use_adaptive_l1_l2_regularizer,
min_value_in_clipping,
max_value_in_clipping,
share_last_block=False):
def _add_objective_module(input_tensor):
# Add GlobalAveragePooling2D
if len(K.int_shape(input_tensor)) == 4:
global_average_pooling_tensor = GlobalAveragePooling2D()(
input_tensor)
else:
global_average_pooling_tensor = input_tensor
if min_value_in_clipping is not None and max_value_in_clipping is not None:
global_average_pooling_tensor = Lambda(
lambda x: K.clip(x,
min_value=min_value_in_clipping,
max_value=max_value_in_clipping))(
global_average_pooling_tensor)
# https://arxiv.org/abs/1801.07698v1 Section 3.2.2 Output setting
# https://arxiv.org/abs/1807.11042
classification_input_tensor = global_average_pooling_tensor
classification_embedding_tensor = BatchNormalization(
scale=True, epsilon=2e-5)(classification_input_tensor)
# Add categorical crossentropy loss
assert len(attribute_name_to_label_encoder_dict) == 1
# label_encoder = attribute_name_to_label_encoder_dict["identity_ID"]
# class_num = len(label_encoder.classes_)
# TODO: hardcoded for Market1501 model
class_num = 751
classification_output_tensor = Dense(
units=class_num,
use_bias=False,
kernel_initializer=RandomNormal(
mean=0.0, stddev=0.001))(classification_embedding_tensor)
classification_output_tensor = Activation("softmax")(
classification_output_tensor)
# Add miscellaneous loss
miscellaneous_input_tensor = global_average_pooling_tensor
miscellaneous_embedding_tensor = miscellaneous_input_tensor
miscellaneous_output_tensor = miscellaneous_input_tensor
return classification_output_tensor, classification_embedding_tensor, miscellaneous_output_tensor, miscellaneous_embedding_tensor
def _apply_concatenation(tensor_list):
if len(tensor_list) == 1:
return tensor_list[0]
else:
return Concatenate()(tensor_list)
def _triplet_hermans_loss(y_true,
y_pred,
metric="euclidean",
margin="soft"):
# Create the loss in two steps:
# 1. Compute all pairwise distances according to the specified metric.
# 2. For each anchor along the first dimension, compute its loss.
dists = cdist(y_pred, y_pred, metric=metric)
loss = batch_hard(dists=dists,
pids=tf.argmax(y_true, axis=-1),
margin=margin)
return loss
# Initiation
classification_output_tensor_list = []
classification_embedding_tensor_list = []
miscellaneous_output_tensor_list = []
miscellaneous_embedding_tensor_list = []
# Initiate the early blocks
model_instantiation = getattr(applications, backbone_model_name, None)
assert model_instantiation is not None, "Backbone {} is not supported.".format(
backbone_model_name)
submodel_list, preprocess_input = model_instantiation(
input_shape=input_shape)
vanilla_input_tensor = Input(shape=K.int_shape(submodel_list[0].input)[1:])
intermediate_output_tensor = vanilla_input_tensor
for submodel in submodel_list[:-1]:
if freeze_backbone_for_N_epochs > 0:
submodel.trainable = False
intermediate_output_tensor = submodel(intermediate_output_tensor)
# Initiate the last blocks
last_block = submodel_list[-1]
last_block_for_global_branch_model = replicate_model(
last_block, name="last_block_for_global_branch")
if freeze_backbone_for_N_epochs > 0:
last_block_for_global_branch_model.trainable = False
if share_last_block:
last_block_for_regional_branch_model = last_block_for_global_branch_model
else:
last_block_for_regional_branch_model = replicate_model(
last_block, name="last_block_for_regional_branch")
if freeze_backbone_for_N_epochs > 0:
last_block_for_regional_branch_model.trainable = False
# Add the global branch
classification_output_tensor, classification_embedding_tensor, miscellaneous_output_tensor, miscellaneous_embedding_tensor = _add_objective_module(
last_block_for_global_branch_model(intermediate_output_tensor))
classification_output_tensor_list.append(classification_output_tensor)
classification_embedding_tensor_list.append(
classification_embedding_tensor)
miscellaneous_output_tensor_list.append(miscellaneous_output_tensor)
miscellaneous_embedding_tensor_list.append(miscellaneous_embedding_tensor)
# Add the regional branch
if region_num > 0:
# Process each region
regional_branch_output_tensor = last_block_for_regional_branch_model(
intermediate_output_tensor)
total_height = K.int_shape(regional_branch_output_tensor)[1]
region_size = total_height // region_num
for region_index in np.arange(region_num):
# Get a slice of feature maps
start_index = region_index * region_size
end_index = (region_index + 1) * region_size
if region_index == region_num - 1:
end_index = total_height
sliced_regional_branch_output_tensor = Lambda(
lambda x, start_index=start_index, end_index=end_index:
x[:, start_index:end_index])(regional_branch_output_tensor)
# Downsampling
sliced_regional_branch_output_tensor = Conv2D(
filters=K.int_shape(sliced_regional_branch_output_tensor)[-1]
// region_num,
kernel_size=3,
padding="same")(sliced_regional_branch_output_tensor)
sliced_regional_branch_output_tensor = Activation("relu")(
sliced_regional_branch_output_tensor)
# Add the regional branch
classification_output_tensor, classification_embedding_tensor, miscellaneous_output_tensor, miscellaneous_embedding_tensor = _add_objective_module(
sliced_regional_branch_output_tensor)
classification_output_tensor_list.append(
classification_output_tensor)
classification_embedding_tensor_list.append(
classification_embedding_tensor)
miscellaneous_output_tensor_list.append(
miscellaneous_output_tensor)
miscellaneous_embedding_tensor_list.append(
miscellaneous_embedding_tensor)
# Define the merged model
embedding_tensor_list = [
_apply_concatenation(miscellaneous_embedding_tensor_list)
]
embedding_size_list = [
K.int_shape(embedding_tensor)[1]
for embedding_tensor in embedding_tensor_list
]
merged_embedding_tensor = _apply_concatenation(embedding_tensor_list)
merged_model = Model(inputs=[vanilla_input_tensor],
outputs=classification_output_tensor_list +
miscellaneous_output_tensor_list +
[merged_embedding_tensor])
merged_model = specify_regularizers(merged_model,
kernel_regularization_factor,
bias_regularization_factor,
gamma_regularization_factor,
beta_regularization_factor,
use_adaptive_l1_l2_regularizer)
# Define the models for training/inference
training_model = Model(inputs=[merged_model.input],
outputs=merged_model.output[:-1],
name="training_model")
inference_model = Model(inputs=[merged_model.input],
outputs=[merged_model.output[-1]],
name="inference_model")
inference_model.embedding_size_list = embedding_size_list
# Compile the model
classification_loss_function_list = [
"categorical_crossentropy"
] * len(classification_output_tensor_list)
triplet_hermans_loss_function = lambda y_true, y_pred: 1.0 * _triplet_hermans_loss(
y_true, y_pred)
miscellaneous_loss_function_list = [
triplet_hermans_loss_function
] * len(miscellaneous_output_tensor_list)
training_model.compile_kwargs = {
"optimizer":
Adam(),
"loss":
classification_loss_function_list + miscellaneous_loss_function_list
}
training_model.compile(**training_model.compile_kwargs)
# Print the summary of the models
# summarize_model(training_model)
# summarize_model(inference_model)
return training_model, inference_model, preprocess_input
def init_model(backbone_model_name, freeze_backbone_for_N_epochs, input_shape,
region_num, attribute_name_to_label_encoder_dict,
kernel_regularization_factor, bias_regularization_factor,
gamma_regularization_factor, beta_regularization_factor,
pooling_mode, min_value, max_value, use_horizontal_flipping):
def _add_pooling_module(input_tensor):
# Add a global pooling layer
output_tensor = input_tensor
if len(K.int_shape(output_tensor)) == 4:
if pooling_mode == "Average":
output_tensor = GlobalAveragePooling2D()(output_tensor)
elif pooling_mode == "Max":
output_tensor = GlobalMaxPooling2D()(output_tensor)
elif pooling_mode == "GeM":
output_tensor = GlobalGeMPooling2D()(output_tensor)
else:
assert False, "{} is an invalid argument!".format(pooling_mode)
# Add the clipping operation
if min_value is not None and max_value is not None:
output_tensor = Lambda(lambda x: K.clip(
x, min_value=min_value, max_value=max_value))(output_tensor)
return output_tensor
def _add_classification_module(input_tensor):
# Add a batch normalization layer
output_tensor = input_tensor
output_tensor = BatchNormalization(epsilon=2e-5)(output_tensor)
# Add a dense layer with softmax activation
label_encoder = attribute_name_to_label_encoder_dict["identity_ID"]
class_num = len(label_encoder.classes_)
output_tensor = Dense(units=class_num,
use_bias=False,
kernel_initializer=RandomNormal(
mean=0.0, stddev=0.001))(output_tensor)
output_tensor = Activation("softmax")(output_tensor)
return output_tensor
def _triplet_hermans_loss(y_true,
y_pred,
metric="euclidean",
margin="soft"):
# Create the loss in two steps:
# 1. Compute all pairwise distances according to the specified metric.
# 2. For each anchor along the first dimension, compute its loss.
dists = cdist(y_pred, y_pred, metric=metric)
loss = batch_hard(dists=dists,
pids=tf.argmax(y_true, axis=-1),
margin=margin)
return loss
# Initiation
miscellaneous_output_tensor_list = []
# Initiate the early blocks
applications_instance = Applications()
model_name_to_model_function = applications_instance.get_model_name_to_model_function(
)
assert backbone_model_name in model_name_to_model_function.keys(
), "Backbone {} is not supported.".format(backbone_model_name)
model_function = model_name_to_model_function[backbone_model_name]
blocks = applications_instance.get_model_in_blocks(
model_function=model_function, include_top=False)
vanilla_input_tensor = Input(shape=input_shape)
intermediate_output_tensor = vanilla_input_tensor
for block in blocks[:-1]:
block = Applications.wrap_block(block, intermediate_output_tensor)
intermediate_output_tensor = block(intermediate_output_tensor)
# Initiate the last blocks
last_block = Applications.wrap_block(blocks[-1],
intermediate_output_tensor)
last_block_for_global_branch_model = replicate_model(
model=last_block, suffix="global_branch")
last_block_for_regional_branch_model = replicate_model(
model=last_block, suffix="regional_branch")
# Add the global branch
miscellaneous_output_tensor = _add_pooling_module(
input_tensor=last_block_for_global_branch_model(
intermediate_output_tensor))
miscellaneous_output_tensor_list.append(miscellaneous_output_tensor)
# Add the regional branch
if region_num > 0:
# Process each region
regional_branch_output_tensor = last_block_for_regional_branch_model(
intermediate_output_tensor)
total_height = K.int_shape(regional_branch_output_tensor)[1]
region_size = total_height // region_num
for region_index in np.arange(region_num):
# Get a slice of feature maps
start_index = region_index * region_size
end_index = (region_index + 1) * region_size
if region_index == region_num - 1:
end_index = total_height
sliced_regional_branch_output_tensor = Lambda(
lambda x, start_index=start_index, end_index=end_index:
x[:, start_index:end_index])(regional_branch_output_tensor)
# Downsampling
sliced_regional_branch_output_tensor = Conv2D(
filters=K.int_shape(sliced_regional_branch_output_tensor)[-1]
// region_num,
kernel_size=3,
padding="same")(sliced_regional_branch_output_tensor)
sliced_regional_branch_output_tensor = Activation("relu")(
sliced_regional_branch_output_tensor)
# Add the regional branch
miscellaneous_output_tensor = _add_pooling_module(
input_tensor=sliced_regional_branch_output_tensor)
miscellaneous_output_tensor_list.append(
miscellaneous_output_tensor)
# Define the model used in inference
inference_model = Model(inputs=[vanilla_input_tensor],
outputs=miscellaneous_output_tensor_list,
name="inference_model")
specify_regularizers(inference_model, kernel_regularization_factor,
bias_regularization_factor,
gamma_regularization_factor,
beta_regularization_factor)
# Define the model used in classification
classification_input_tensor_list = [
Input(shape=K.int_shape(item)[1:])
for item in miscellaneous_output_tensor_list
]
classification_output_tensor_list = []
for classification_input_tensor in classification_input_tensor_list:
classification_output_tensor = _add_classification_module(
input_tensor=classification_input_tensor)
classification_output_tensor_list.append(classification_output_tensor)
classification_model = Model(inputs=classification_input_tensor_list,
outputs=classification_output_tensor_list,
name="classification_model")
specify_regularizers(classification_model, kernel_regularization_factor,
bias_regularization_factor,
gamma_regularization_factor,
beta_regularization_factor)
# Define the model used in training
expand = lambda x: x if isinstance(x, list) else [x]
vanilla_input_tensor = Input(shape=K.int_shape(inference_model.input)[1:])
vanilla_feature_tensor_list = expand(inference_model(vanilla_input_tensor))
if use_horizontal_flipping:
flipped_input_tensor = tf.image.flip_left_right(vanilla_input_tensor)
flipped_feature_tensor_list = expand(
inference_model(flipped_input_tensor))
merged_feature_tensor_list = [
sum(item_tuple) / 2 for item_tuple in zip(
vanilla_feature_tensor_list, flipped_feature_tensor_list)
]
else:
merged_feature_tensor_list = vanilla_feature_tensor_list
miscellaneous_output_tensor_list = merged_feature_tensor_list
classification_output_tensor_list = expand(
classification_model(merged_feature_tensor_list))
training_model = Model(inputs=[vanilla_input_tensor],
outputs=miscellaneous_output_tensor_list +
classification_output_tensor_list,
name="training_model")
# Add the flipping loss
if use_horizontal_flipping:
flipping_loss_list = [
K.mean(mean_squared_error(*item_tuple)) for item_tuple in zip(
vanilla_feature_tensor_list, flipped_feature_tensor_list)
]
flipping_loss = sum(flipping_loss_list)
training_model.add_metric(flipping_loss,
name="flipping",
aggregation="mean")
training_model.add_loss(1.0 * flipping_loss)
# Compile the model
triplet_hermans_loss_function = lambda y_true, y_pred: 1.0 * _triplet_hermans_loss(
y_true, y_pred)
miscellaneous_loss_function_list = [
triplet_hermans_loss_function
] * len(miscellaneous_output_tensor_list)
categorical_crossentropy_loss_function = lambda y_true, y_pred: 1.0 * categorical_crossentropy(
y_true, y_pred, from_logits=False, label_smoothing=0.0)
classification_loss_function_list = [
categorical_crossentropy_loss_function
] * len(classification_output_tensor_list)
training_model.compile_kwargs = {
"optimizer":
Adam(),
"loss":
miscellaneous_loss_function_list + classification_loss_function_list
}
if freeze_backbone_for_N_epochs > 0:
specify_trainable(model=training_model,
trainable=False,
keywords=[block.name for block in blocks])
training_model.compile(**training_model.compile_kwargs)
# Print the summary of the training model
summarize_model(training_model)
return training_model, inference_model
