def build_model(self) -> tf.keras.Model:
"""Builds segmentation model."""
input_specs = tf.keras.layers.InputSpec(
shape=[None] + self.task_config.model.input_size +
[self.task_config.model.num_channels],
dtype=self.task_config.train_data.dtype)
l2_weight_decay = self.task_config.losses.l2_weight_decay
# Divide weight decay by 2.0 to match the implementation of tf.nn.l2_loss.
# (https://www.tensorflow.org/api_docs/python/tf/keras/regularizers/l2)
# (https://www.tensorflow.org/api_docs/python/tf/nn/l2_loss)
l2_regularizer = (tf.keras.regularizers.l2(l2_weight_decay / 2.0)
if l2_weight_decay else None)
model = factory.build_segmentation_model_3d(
input_specs=input_specs,
model_config=self.task_config.model,
l2_regularizer=l2_regularizer)
# Create a dummy input and call model instance to initialize the model. This
# is needed when launching multiple experiments using the same model
# directory. Since there is already a trained model, forward pass will not
# run and the model will never be built. This is only done when spatial
# partitioning is not enabled; otherwise it will fail with OOM due to
# extremely large input.
if (not self.task_config.train_input_partition_dims) and (
not self.task_config.eval_input_partition_dims):
dummy_input = tf.random.uniform(shape=[1] +
list(input_specs.shape[1:]))
_ = model(dummy_input)
return model
def _build_model(self) -> tf.keras.Model:
"""Builds and returns a segmentation model."""
num_channels = self.params.task.model.num_channels
input_specs = tf.keras.layers.InputSpec(
shape=[self._batch_size] + self._input_image_size + [num_channels])
return factory.build_segmentation_model_3d(
input_specs=input_specs,
model_config=self.params.task.model,
l2_regularizer=None)
def test_unet3d_builder(self, input_size, weight_decay):
num_classes = 3
input_specs = tf.keras.layers.InputSpec(
shape=[None, input_size[0], input_size[1], input_size[2], 3])
model_config = exp_cfg.SemanticSegmentationModel3D(num_classes=num_classes)
l2_regularizer = (
tf.keras.regularizers.l2(weight_decay) if weight_decay else None)
model = factory.build_segmentation_model_3d(
input_specs=input_specs,
model_config=model_config,
l2_regularizer=l2_regularizer)
self.assertIsInstance(
model, tf.keras.Model,
'Output should be a tf.keras.Model instance but got %s' % type(model))