def classifier_model(bert_config,
num_labels,
max_seq_length,
final_layer_initializer=None,
hub_module_url=None):
"""BERT classifier model in functional API style.
Construct a Keras model for predicting `num_labels` outputs from an input with
maximum sequence length `max_seq_length`.
Args:
bert_config: BertConfig or AlbertConfig, the config defines the core
BERT or ALBERT model.
num_labels: integer, the number of classes.
max_seq_length: integer, the maximum input sequence length.
final_layer_initializer: Initializer for final dense layer. Defaulted
TruncatedNormal initializer.
hub_module_url: TF-Hub path/url to Bert module.
Returns:
Combined prediction model (words, mask, type) -> (one-hot labels)
BERT sub-model (words, mask, type) -> (bert_outputs)
"""
if final_layer_initializer is not None:
initializer = final_layer_initializer
else:
initializer = tf.keras.initializers.TruncatedNormal(
stddev=bert_config.initializer_range)
if not hub_module_url:
bert_encoder = get_transformer_encoder(bert_config, max_seq_length)
return bert_classifier.BertClassifier(
bert_encoder,
num_classes=num_labels,
dropout_rate=bert_config.hidden_dropout_prob,
initializer=initializer), bert_encoder
input_word_ids = tf.keras.layers.Input(
shape=(max_seq_length,), dtype=tf.int32, name='input_word_ids')
input_mask = tf.keras.layers.Input(
shape=(max_seq_length,), dtype=tf.int32, name='input_mask')
input_type_ids = tf.keras.layers.Input(
shape=(max_seq_length,), dtype=tf.int32, name='input_type_ids')
bert_model = hub.KerasLayer(hub_module_url, trainable=True)
pooled_output, _ = bert_model([input_word_ids, input_mask, input_type_ids])
output = tf.keras.layers.Dropout(rate=bert_config.hidden_dropout_prob)(
pooled_output)
output = tf.keras.layers.Dense(
num_labels,
kernel_initializer=initializer,
name='output')(
output)
return tf.keras.Model(
inputs={
'input_word_ids': input_word_ids,
'input_mask': input_mask,
'input_type_ids': input_type_ids
},
outputs=output), bert_model
def test_bert_trainer(self):
"""Validate that the Keras object can be created."""
# Build a transformer network to use within the BERT trainer.
vocab_size = 100
sequence_length = 512
test_network = networks.TransformerEncoder(
vocab_size=vocab_size, num_layers=2, sequence_length=sequence_length)
# Create a BERT trainer with the created network.
num_classes = 3
bert_trainer_model = bert_classifier.BertClassifier(
test_network,
num_classes=num_classes)
# Create a set of 2-dimensional inputs (the first dimension is implicit).
word_ids = tf.keras.Input(shape=(sequence_length,), dtype=tf.int32)
mask = tf.keras.Input(shape=(sequence_length,), dtype=tf.int32)
type_ids = tf.keras.Input(shape=(sequence_length,), dtype=tf.int32)
# Invoke the trainer model on the inputs. This causes the layer to be built.
cls_outs = bert_trainer_model([word_ids, mask, type_ids])
# Validate that the outputs are of the expected shape.
expected_classification_shape = [None, num_classes]
self.assertAllEqual(expected_classification_shape, cls_outs.shape.as_list())
def test_bert_trainer_tensor_call(self):
"""Validate that the Keras object can be invoked."""
# Build a transformer network to use within the BERT trainer. (Here, we use
# a short sequence_length for convenience.)
test_network = networks.TransformerEncoder(
vocab_size=100, num_layers=2, sequence_length=2)
# Create a BERT trainer with the created network.
bert_trainer_model = bert_classifier.BertClassifier(
test_network, num_classes=2)
# Create a set of 2-dimensional data tensors to feed into the model.
word_ids = tf.constant([[1, 1], [2, 2]], dtype=tf.int32)
mask = tf.constant([[1, 1], [1, 0]], dtype=tf.int32)
type_ids = tf.constant([[1, 1], [2, 2]], dtype=tf.int32)
# Invoke the trainer model on the tensors. In Eager mode, this does the
# actual calculation. (We can't validate the outputs, since the network is
# too complex: this simply ensures we're not hitting runtime errors.)
_ = bert_trainer_model([word_ids, mask, type_ids])
def test_serialize_deserialize(self):
"""Validate that the BERT trainer can be serialized and deserialized."""
# Build a transformer network to use within the BERT trainer. (Here, we use
# a short sequence_length for convenience.)
test_network = networks.TransformerEncoder(
vocab_size=100, num_layers=2, sequence_length=5)
# Create a BERT trainer with the created network. (Note that all the args
# are different, so we can catch any serialization mismatches.)
bert_trainer_model = bert_classifier.BertClassifier(
test_network, num_classes=4, initializer='zeros', output='predictions')
# Create another BERT trainer via serialization and deserialization.
config = bert_trainer_model.get_config()
new_bert_trainer_model = bert_classifier.BertClassifier.from_config(config)
# Validate that the config can be forced to JSON.
_ = new_bert_trainer_model.to_json()
# If the serialization was successful, the new config should match the old.
self.assertAllEqual(bert_trainer_model.get_config(),
new_bert_trainer_model.get_config())
def classifier_model(bert_config,
float_type,
num_labels,
max_seq_length,
final_layer_initializer=None,
hub_module_url=None):
"""BERT classifier model in functional API style.
Construct a Keras model for predicting `num_labels` outputs from an input with
maximum sequence length `max_seq_length`.
Args:
bert_config: BertConfig, the config defines the core BERT model.
float_type: dtype, tf.float32 or tf.bfloat16.
num_labels: integer, the number of classes.
max_seq_length: integer, the maximum input sequence length.
final_layer_initializer: Initializer for final dense layer. Defaulted
TruncatedNormal initializer.
hub_module_url: TF-Hub path/url to Bert module.
Returns:
Combined prediction model (words, mask, type) -> (one-hot labels)
BERT sub-model (words, mask, type) -> (bert_outputs)
"""
if final_layer_initializer is not None:
initializer = final_layer_initializer
else:
initializer = tf.keras.initializers.TruncatedNormal(
stddev=bert_config.initializer_range)
if not hub_module_url:
bert_encoder = networks.TransformerEncoder(
vocab_size=bert_config.vocab_size,
hidden_size=bert_config.hidden_size,
num_layers=bert_config.num_hidden_layers,
num_attention_heads=bert_config.num_attention_heads,
intermediate_size=bert_config.intermediate_size,
activation=tf_utils.get_activation('gelu'),
dropout_rate=bert_config.hidden_dropout_prob,
attention_dropout_rate=bert_config.attention_probs_dropout_prob,
sequence_length=max_seq_length,
max_sequence_length=bert_config.max_position_embeddings,
type_vocab_size=bert_config.type_vocab_size,
initializer=tf.keras.initializers.TruncatedNormal(
stddev=bert_config.initializer_range))
return bert_classifier.BertClassifier(
bert_encoder,
num_classes=num_labels,
dropout_rate=bert_config.hidden_dropout_prob,
initializer=initializer), bert_encoder
input_word_ids = tf.keras.layers.Input(shape=(max_seq_length, ),
dtype=tf.int32,
name='input_word_ids')
input_mask = tf.keras.layers.Input(shape=(max_seq_length, ),
dtype=tf.int32,
name='input_mask')
input_type_ids = tf.keras.layers.Input(shape=(max_seq_length, ),
dtype=tf.int32,
name='input_type_ids')
bert_model = hub.KerasLayer(hub_module_url, trainable=True)
pooled_output, _ = bert_model([input_word_ids, input_mask, input_type_ids])
output = tf.keras.layers.Dropout(
rate=bert_config.hidden_dropout_prob)(pooled_output)
output = tf.keras.layers.Dense(num_labels,
kernel_initializer=initializer,
name='output',
dtype=float_type)(output)
return tf.keras.Model(inputs={
'input_word_ids': input_word_ids,
'input_mask': input_mask,
'input_type_ids': input_type_ids
},
outputs=output), bert_model
