Training settings
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Neural network architecture
sys.path.append('./resources/libraries')
import os
import tensorflow as tf
from tensorflow.keras.optimizers.legacy import Adam
from tensorflow.keras.applications import MobileNetV2
from tensorflow.keras.layers import BatchNormalization, Conv2D, Softmax, Reshape
from tensorflow.keras.models import Model
from ei_tensorflow.constrained_object_detection import models, dataset, metrics, util
from ei_tensorflow.velo import train_keras_model_with_velo
from ei_shared.pretrained_weights import get_or_download_pretrained_weights
import ei_tensorflow.training
WEIGHTS_PREFIX = os.environ.get('WEIGHTS_PREFIX', os.getcwd())
def build_model(input_shape: tuple, weights: str, alpha: float,
num_classes: int) -> tf.keras.Model:
""" Construct a constrained object detection model.
Args:
input_shape: Passed to MobileNet construction.
weights: Weights for initialization of MobileNet where None implies
random initialization.
alpha: MobileNet alpha value.
num_classes: Number of classes, i.e. final dimension size, in output.
Returns:
Uncompiled keras model.
Model takes (B, H, W, C) input and
returns (B, H//8, W//8, num_classes) logits.
"""
#! First create full mobile_net_V2 from (HW, HW, C) input
#! to (HW/8, HW/8, C) output
mobile_net_v2 = MobileNetV2(input_shape=input_shape,
weights=weights,
alpha=alpha,
include_top=True)
#! Default batch norm is configured for huge networks, let's speed it up
for layer in mobile_net_v2.layers:
if type(layer) == BatchNormalization:
layer.momentum = 0.9
#! Cut MobileNet where it hits 1/8th input resolution; i.e. (HW/8, HW/8, C)
cut_point = mobile_net_v2.get_layer('block_6_expand_relu')
#! Now attach a small additional head on the MobileNet
model = Conv2D(filters=32, kernel_size=1, strides=1,
activation='relu', name='head')(cut_point.output)
logits = Conv2D(filters=num_classes, kernel_size=1, strides=1,
activation=None, name='logits')(model)
return Model(inputs=mobile_net_v2.input, outputs=logits)
def train(num_classes: int, learning_rate: float, num_epochs: int,
alpha: float, object_weight: float,
train_dataset: tf.data.Dataset,
validation_dataset: tf.data.Dataset,
best_model_path: str,
input_shape: tuple,
batch_size: int,
use_velo: bool = False,
ensure_determinism: bool = False) -> tf.keras.Model:
""" Construct and train a constrained object detection model.
Args:
num_classes: Number of classes in datasets. This does not include
implied background class introduced by segmentation map dataset
conversion.
learning_rate: Learning rate for Adam.
num_epochs: Number of epochs passed to model.fit
alpha: Alpha used to construct MobileNet. Pretrained weights will be
used if there is a matching set.
object_weight: The weighting to give the object in the loss function
where background has an implied weight of 1.0.
train_dataset: Training dataset of (x, (bbox, one_hot_y))
validation_dataset: Validation dataset of (x, (bbox, one_hot_y))
best_model_path: location to save best model path. note: weights
will be restored from this path based on best val_f1 score.
input_shape: The shape of the model's input
batch_size: Training batch size
ensure_determinism: If true, functions that may be non-
deterministic are disabled (e.g. autotuning prefetch). This
should be true in test environments.
Returns:
Trained keras model.
Constructs a new constrained object detection model with num_classes+1
outputs (denoting the classes with an implied background class of 0).
Both training and validation datasets are adapted from
(x, (bbox, one_hot_y)) to (x, segmentation_map). Model is trained with a
custom weighted cross entropy function.
"""
nonlocal callbacks
num_classes_with_background = num_classes + 1
width, height, input_num_channels = input_shape
if width != height:
raise Exception(f"Only square inputs are supported; not {input_shape}")
#! Use pretrained weights, if we have them for configured
allowed_combinations = [{'num_channels': 1, 'alpha': 0.1},
{'num_channels': 1, 'alpha': 0.35},
{'num_channels': 3, 'alpha': 0.1},
{'num_channels': 3, 'alpha': 0.35}]
weights = get_or_download_pretrained_weights(WEIGHTS_PREFIX, input_num_channels, alpha, allowed_combinations)
model = build_model(
input_shape=input_shape,
weights=weights,
alpha=alpha,
num_classes=num_classes_with_background
)
#! Derive output size from model
model_output_shape = model.layers[-1].output.shape
_batch, width, height, num_classes = model_output_shape
if width != height:
raise Exception(f"Only square outputs are supported; not {model_output_shape}")
output_width_height = width
#! Build weighted cross entropy loss specific to this model size
weighted_xent = models.construct_weighted_xent_fn(model.output.shape, object_weight)
prefetch_policy = 1 if ensure_determinism else tf.data.experimental.AUTOTUNE
#! Transform bounding box labels into segmentation maps
def as_segmentation(ds, shuffle):
ds = ds.map(dataset.bbox_to_segmentation(output_width_height, num_classes_with_background))
if not ensure_determinism and shuffle:
ds = ds.shuffle(buffer_size=batch_size*4)
ds = ds.batch(batch_size, drop_remainder=False).prefetch(prefetch_policy)
return ds
train_segmentation_dataset = as_segmentation(train_dataset, True)
validation_segmentation_dataset = as_segmentation(validation_dataset, False)
validation_dataset_for_callback = (validation_dataset
.batch(batch_size, drop_remainder=False)
.prefetch(prefetch_policy))
#! Initialise bias of final classifier based on training data prior.
util.set_classifier_biases_from_dataset(
model, train_segmentation_dataset)
if not use_velo:
model.compile(loss=weighted_xent,
optimizer=Adam(learning_rate=learning_rate))
#! Create callback that will do centroid scoring on end of epoch against
#! validation data. Include a callback to show % progress in slow cases.
callbacks = callbacks if callbacks else []
callbacks.append(metrics.CentroidScoring(validation_dataset_for_callback,
output_width_height, num_classes_with_background))
callbacks.append(metrics.PrintPercentageTrained(num_epochs))
#! Include a callback for model checkpointing based on the best validation f1.
callbacks.append(
tf.keras.callbacks.ModelCheckpoint(best_model_path,
monitor='val_f1', save_best_only=True, mode='max',
save_weights_only=True, verbose=0))
if use_velo:
from tensorflow.python.framework.errors_impl import ResourceExhaustedError
try:
train_keras_model_with_velo(
model,
train_segmentation_dataset,
validation_segmentation_dataset,
loss_fn=weighted_xent,
num_epochs=num_epochs,
callbacks=callbacks
)
except ResourceExhaustedError as e:
print(str(e))
raise Exception(
"ResourceExhaustedError caught during train_keras_model_with_velo."
" Though VeLO encourages a large batch size, the current"
f" size of {batch_size} may be too large. Please try a lower"
" value. For further assistance please contact support"
" at https://forum.edgeimpulse.com/")
else:
model.fit(train_segmentation_dataset,
validation_data=validation_segmentation_dataset,
epochs=num_epochs, callbacks=callbacks, verbose=0)
#! Restore best weights.
model.load_weights(best_model_path)
#! Add explicit softmax layer before export.
softmax_layer = Softmax()(model.layers[-1].output)
model = Model(model.input, softmax_layer)
return model
EPOCHS = args.epochs or 60
LEARNING_RATE = args.learning_rate or 0.001
BATCH_SIZE = args.batch_size or 32
model = train(num_classes=classes,
learning_rate=LEARNING_RATE,
num_epochs=EPOCHS,
alpha=0.35,
object_weight=100,
train_dataset=train_dataset,
validation_dataset=validation_dataset,
best_model_path=BEST_MODEL_PATH,
input_shape=MODEL_INPUT_SHAPE,
batch_size=BATCH_SIZE,
use_velo=False,
ensure_determinism=ensure_determinism)
disable_per_channel_quantization = False
Input layer (4,096 features)
FOMO (Faster Objects, More Objects) MobileNetV2 0.35
Output layer (1 classes)
Model
Model version: