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Commit e5f021ce authored by Hongkun Yu's avatar Hongkun Yu Committed by A. Unique TensorFlower
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[Refactor] Deprecate nlp/bert_modeling.py as the bert models are using new implementation. 

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# Copyright 2019 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.
# ==============================================================================
"""The main BERT model and related functions."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import copy
import math
import tensorflow as tf
from tensorflow.python.util import deprecation
from official.modeling import tf_utils
from official.nlp.bert import configs
@deprecation.deprecated(None, "The function should not be used any more.")
def get_bert_model(input_word_ids,
input_mask,
input_type_ids,
config=None,
name=None,
float_type=tf.float32):
"""Wraps the core BERT model as a keras.Model."""
bert_model_layer = BertModel(config=config, float_type=float_type, name=name)
pooled_output, sequence_output = bert_model_layer(input_word_ids, input_mask,
input_type_ids)
bert_model = tf.keras.Model(
inputs=[input_word_ids, input_mask, input_type_ids],
outputs=[pooled_output, sequence_output])
return bert_model
class BertModel(tf.keras.layers.Layer):
"""BERT model ("Bidirectional Encoder Representations from Transformers").
Example usage:
```python
# Already been converted into WordPiece token ids
input_word_ids = tf.constant([[31, 51, 99], [15, 5, 0]])
input_mask = tf.constant([[1, 1, 1], [1, 1, 0]])
input_type_ids = tf.constant([[0, 0, 1], [0, 2, 0]])
config = configs.BertConfig(vocab_size=32000, hidden_size=512,
num_hidden_layers=8, num_attention_heads=6, intermediate_size=1024)
pooled_output, sequence_output = modeling.BertModel(config=config)(
input_word_ids=input_word_ids,
input_mask=input_mask,
input_type_ids=input_type_ids)
...
```
"""
@deprecation.deprecated(
None, "Please use `nlp.modeling.networks.TransformerEncoder` instead.")
def __init__(self, config, float_type=tf.float32, **kwargs):
super(BertModel, self).__init__(**kwargs)
self.config = (
configs.BertConfig.from_dict(config)
if isinstance(config, dict) else copy.deepcopy(config))
self.float_type = float_type
def build(self, unused_input_shapes):
"""Implements build() for the layer."""
self.embedding_lookup = EmbeddingLookup(
vocab_size=self.config.vocab_size,
embedding_size=self.config.hidden_size,
initializer_range=self.config.initializer_range,
dtype=tf.float32,
name="word_embeddings")
self.embedding_postprocessor = EmbeddingPostprocessor(
use_type_embeddings=True,
token_type_vocab_size=self.config.type_vocab_size,
use_position_embeddings=True,
max_position_embeddings=self.config.max_position_embeddings,
dropout_prob=self.config.hidden_dropout_prob,
initializer_range=self.config.initializer_range,
dtype=tf.float32,
name="embedding_postprocessor")
self.encoder = Transformer(
num_hidden_layers=self.config.num_hidden_layers,
hidden_size=self.config.hidden_size,
num_attention_heads=self.config.num_attention_heads,
intermediate_size=self.config.intermediate_size,
intermediate_activation=self.config.hidden_act,
hidden_dropout_prob=self.config.hidden_dropout_prob,
attention_probs_dropout_prob=self.config.attention_probs_dropout_prob,
initializer_range=self.config.initializer_range,
backward_compatible=self.config.backward_compatible,
float_type=self.float_type,
name="encoder")
self.pooler_transform = tf.keras.layers.Dense(
units=self.config.hidden_size,
activation="tanh",
kernel_initializer=get_initializer(self.config.initializer_range),
name="pooler_transform")
super(BertModel, self).build(unused_input_shapes)
def __call__(self,
input_word_ids,
input_mask=None,
input_type_ids=None,
**kwargs):
inputs = tf_utils.pack_inputs([input_word_ids, input_mask, input_type_ids])
return super(BertModel, self).__call__(inputs, **kwargs)
def call(self, inputs, mode="bert"):
"""Implements call() for the layer.
Args:
inputs: packed input tensors.
mode: string, `bert` or `encoder`.
Returns:
Output tensor of the last layer for BERT training (mode=`bert`) which
is a float Tensor of shape [batch_size, seq_length, hidden_size] or
a list of output tensors for encoder usage (mode=`encoder`).
"""
unpacked_inputs = tf_utils.unpack_inputs(inputs)
input_word_ids = unpacked_inputs[0]
input_mask = unpacked_inputs[1]
input_type_ids = unpacked_inputs[2]
word_embeddings = self.embedding_lookup(input_word_ids)
embedding_tensor = self.embedding_postprocessor(
word_embeddings=word_embeddings, token_type_ids=input_type_ids)
if self.float_type == tf.float16:
embedding_tensor = tf.cast(embedding_tensor, tf.float16)
attention_mask = None
if input_mask is not None:
attention_mask = create_attention_mask_from_input_mask(
input_word_ids, input_mask)
if mode == "encoder":
return self.encoder(
embedding_tensor, attention_mask, return_all_layers=True)
sequence_output = self.encoder(embedding_tensor, attention_mask)
first_token_tensor = tf.squeeze(sequence_output[:, 0:1, :], axis=1)
pooled_output = self.pooler_transform(first_token_tensor)
return (pooled_output, sequence_output)
def get_config(self):
config = {"config": self.config.to_dict()}
base_config = super(BertModel, self).get_config()
return dict(list(base_config.items()) + list(config.items()))
class EmbeddingLookup(tf.keras.layers.Layer):
"""Looks up words embeddings for id tensor."""
def __init__(self,
vocab_size,
embedding_size=768,
initializer_range=0.02,
**kwargs):
super(EmbeddingLookup, self).__init__(**kwargs)
self.vocab_size = vocab_size
self.embedding_size = embedding_size
self.initializer_range = initializer_range
def build(self, unused_input_shapes):
"""Implements build() for the layer."""
self.embeddings = self.add_weight(
"embeddings",
shape=[self.vocab_size, self.embedding_size],
initializer=get_initializer(self.initializer_range),
dtype=self.dtype)
super(EmbeddingLookup, self).build(unused_input_shapes)
def call(self, inputs):
"""Implements call() for the layer."""
input_shape = tf_utils.get_shape_list(inputs)
flat_input = tf.reshape(inputs, [-1])
output = tf.gather(self.embeddings, flat_input)
output = tf.reshape(output, input_shape + [self.embedding_size])
return output
class EmbeddingPostprocessor(tf.keras.layers.Layer):
"""Performs various post-processing on a word embedding tensor."""
def __init__(self,
use_type_embeddings=False,
token_type_vocab_size=None,
use_position_embeddings=True,
max_position_embeddings=512,
dropout_prob=0.0,
initializer_range=0.02,
initializer=None,
**kwargs):
super(EmbeddingPostprocessor, self).__init__(**kwargs)
self.use_type_embeddings = use_type_embeddings
self.token_type_vocab_size = token_type_vocab_size
self.use_position_embeddings = use_position_embeddings
self.max_position_embeddings = max_position_embeddings
self.dropout_prob = dropout_prob
self.initializer_range = initializer_range
if not initializer:
self.initializer = get_initializer(self.initializer_range)
else:
self.initializer = initializer
if self.use_type_embeddings and not self.token_type_vocab_size:
raise ValueError("If `use_type_embeddings` is True, then "
"`token_type_vocab_size` must be specified.")
def build(self, input_shapes):
"""Implements build() for the layer."""
(word_embeddings_shape, _) = input_shapes
width = word_embeddings_shape.as_list()[-1]
self.type_embeddings = None
if self.use_type_embeddings:
self.type_embeddings = self.add_weight(
"type_embeddings",
shape=[self.token_type_vocab_size, width],
initializer=get_initializer(self.initializer_range),
dtype=self.dtype)
self.position_embeddings = None
if self.use_position_embeddings:
self.position_embeddings = self.add_weight(
"position_embeddings",
shape=[self.max_position_embeddings, width],
initializer=get_initializer(self.initializer_range),
dtype=self.dtype)
self.output_layer_norm = tf.keras.layers.LayerNormalization(
name="layer_norm", axis=-1, epsilon=1e-12, dtype=tf.float32)
self.output_dropout = tf.keras.layers.Dropout(
rate=self.dropout_prob, dtype=tf.float32)
super(EmbeddingPostprocessor, self).build(input_shapes)
def __call__(self, word_embeddings, token_type_ids=None, **kwargs):
inputs = tf_utils.pack_inputs([word_embeddings, token_type_ids])
return super(EmbeddingPostprocessor, self).__call__(inputs, **kwargs)
def call(self, inputs):
"""Implements call() for the layer."""
unpacked_inputs = tf_utils.unpack_inputs(inputs)
word_embeddings = unpacked_inputs[0]
token_type_ids = unpacked_inputs[1]
input_shape = tf_utils.get_shape_list(word_embeddings, expected_rank=3)
batch_size = input_shape[0]
seq_length = input_shape[1]
width = input_shape[2]
output = word_embeddings
if self.use_type_embeddings:
flat_token_type_ids = tf.reshape(token_type_ids, [-1])
token_type_embeddings = tf.gather(self.type_embeddings,
flat_token_type_ids)
token_type_embeddings = tf.reshape(token_type_embeddings,
[batch_size, seq_length, width])
output += token_type_embeddings
if self.use_position_embeddings:
position_embeddings = tf.expand_dims(
tf.slice(self.position_embeddings, [0, 0], [seq_length, width]),
axis=0)
output += position_embeddings
output = self.output_layer_norm(output)
output = self.output_dropout(output)
return output
class Attention(tf.keras.layers.Layer):
"""Performs multi-headed attention from `from_tensor` to `to_tensor`.
This is an implementation of multi-headed attention based on "Attention
is all you Need". If `from_tensor` and `to_tensor` are the same, then
this is self-attention. Each timestep in `from_tensor` attends to the
corresponding sequence in `to_tensor`, and returns a fixed-with vector.
This function first projects `from_tensor` into a "query" tensor and
`to_tensor` into "key" and "value" tensors. These are (effectively) a list
of tensors of length `num_attention_heads`, where each tensor is of shape
[batch_size, seq_length, size_per_head].
Then, the query and key tensors are dot-producted and scaled. These are
softmaxed to obtain attention probabilities. The value tensors are then
interpolated by these probabilities, then concatenated back to a single
tensor and returned.
In practice, the multi-headed attention are done with tf.einsum as follows:
Input_tensor: [BFD]
Wq, Wk, Wv: [DNH]
Q:[BFNH] = einsum('BFD,DNH->BFNH', Input_tensor, Wq)
K:[BTNH] = einsum('BTD,DNH->BTNH', Input_tensor, Wk)
V:[BTNH] = einsum('BTD,DNH->BTNH', Input_tensor, Wv)
attention_scores:[BNFT] = einsum('BTNH,BFNH->BNFT', K, Q) / sqrt(H)
attention_probs:[BNFT] = softmax(attention_scores)
context_layer:[BFNH] = einsum('BNFT,BTNH->BFNH', attention_probs, V)
Wout:[DNH]
Output:[BFD] = einsum('BFNH,DNH>BFD', context_layer, Wout)
"""
def __init__(self,
num_attention_heads=12,
size_per_head=64,
attention_probs_dropout_prob=0.0,
initializer_range=0.02,
backward_compatible=False,
**kwargs):
super(Attention, self).__init__(**kwargs)
self.num_attention_heads = num_attention_heads
self.size_per_head = size_per_head
self.attention_probs_dropout_prob = attention_probs_dropout_prob
self.initializer_range = initializer_range
self.backward_compatible = backward_compatible
def build(self, unused_input_shapes):
"""Implements build() for the layer."""
self.query_dense = self._projection_dense_layer("query")
self.key_dense = self._projection_dense_layer("key")
self.value_dense = self._projection_dense_layer("value")
self.attention_probs_dropout = tf.keras.layers.Dropout(
rate=self.attention_probs_dropout_prob)
super(Attention, self).build(unused_input_shapes)
def reshape_to_matrix(self, input_tensor):
"""Reshape N > 2 rank tensor to rank 2 tensor for performance."""
ndims = input_tensor.shape.ndims
if ndims < 2:
raise ValueError("Input tensor must have at least rank 2."
"Shape = %s" % (input_tensor.shape))
if ndims == 2:
return input_tensor
width = input_tensor.shape[-1]
output_tensor = tf.reshape(input_tensor, [-1, width])
return output_tensor
def __call__(self, from_tensor, to_tensor, attention_mask=None, **kwargs):
inputs = tf_utils.pack_inputs([from_tensor, to_tensor, attention_mask])
return super(Attention, self).__call__(inputs, **kwargs)
def call(self, inputs):
"""Implements call() for the layer."""
(from_tensor, to_tensor, attention_mask) = tf_utils.unpack_inputs(inputs)
# Scalar dimensions referenced here:
# B = batch size (number of sequences)
# F = `from_tensor` sequence length
# T = `to_tensor` sequence length
# N = `num_attention_heads`
# H = `size_per_head`
# `query_tensor` = [B, F, N ,H]
query_tensor = self.query_dense(from_tensor)
# `key_tensor` = [B, T, N, H]
key_tensor = self.key_dense(to_tensor)
# `value_tensor` = [B, T, N, H]
value_tensor = self.value_dense(to_tensor)
# Take the dot product between "query" and "key" to get the raw
# attention scores.
attention_scores = tf.einsum("BTNH,BFNH->BNFT", key_tensor, query_tensor)
attention_scores = tf.multiply(attention_scores,
1.0 / math.sqrt(float(self.size_per_head)))
if attention_mask is not None:
# `attention_mask` = [B, 1, F, T]
attention_mask = tf.expand_dims(attention_mask, axis=[1])
# Since attention_mask is 1.0 for positions we want to attend and 0.0 for
# masked positions, this operation will create a tensor which is 0.0 for
# positions we want to attend and -10000.0 for masked positions.
adder = (1.0 - tf.cast(attention_mask, attention_scores.dtype)) * -10000.0
# Since we are adding it to the raw scores before the softmax, this is
# effectively the same as removing these entirely.
attention_scores += adder
# Normalize the attention scores to probabilities.
# `attention_probs` = [B, N, F, T]
attention_probs = tf.nn.softmax(attention_scores)
# This is actually dropping out entire tokens to attend to, which might
# seem a bit unusual, but is taken from the original Transformer paper.
attention_probs = self.attention_probs_dropout(attention_probs)
# `context_layer` = [B, F, N, H]
context_tensor = tf.einsum("BNFT,BTNH->BFNH", attention_probs, value_tensor)
return context_tensor
def _projection_dense_layer(self, name):
"""A helper to define a projection layer."""
return Dense3D(
num_attention_heads=self.num_attention_heads,
size_per_head=self.size_per_head,
kernel_initializer=get_initializer(self.initializer_range),
output_projection=False,
backward_compatible=self.backward_compatible,
name=name)
class Dense3D(tf.keras.layers.Layer):
"""A Dense Layer using 3D kernel with tf.einsum implementation.
Attributes:
num_attention_heads: An integer, number of attention heads for each
multihead attention layer.
size_per_head: An integer, hidden size per attention head.
hidden_size: An integer, dimension of the hidden layer.
kernel_initializer: An initializer for the kernel weight.
bias_initializer: An initializer for the bias.
activation: An activation function to use. If nothing is specified, no
activation is applied.
use_bias: A bool, whether the layer uses a bias.
output_projection: A bool, whether the Dense3D layer is used for output
linear projection.
backward_compatible: A bool, whether the variables shape are compatible with
checkpoints converted from TF 1.x.
"""
def __init__(self,
num_attention_heads=12,
size_per_head=72,
kernel_initializer=None,
bias_initializer="zeros",
activation=None,
use_bias=True,
output_projection=False,
backward_compatible=False,
**kwargs):
"""Inits Dense3D."""
super(Dense3D, self).__init__(**kwargs)
self.num_attention_heads = num_attention_heads
self.size_per_head = size_per_head
self.hidden_size = num_attention_heads * size_per_head
self.kernel_initializer = kernel_initializer
self.bias_initializer = bias_initializer
self.activation = activation
self.use_bias = use_bias
self.output_projection = output_projection
self.backward_compatible = backward_compatible
@property
def compatible_kernel_shape(self):
if self.output_projection:
return [self.hidden_size, self.hidden_size]
return [self.last_dim, self.hidden_size]
@property
def compatible_bias_shape(self):
return [self.hidden_size]
@property
def kernel_shape(self):
if self.output_projection:
return [self.num_attention_heads, self.size_per_head, self.hidden_size]
return [self.last_dim, self.num_attention_heads, self.size_per_head]
@property
def bias_shape(self):
if self.output_projection:
return [self.hidden_size]
return [self.num_attention_heads, self.size_per_head]
def build(self, input_shape):
"""Implements build() for the layer."""
dtype = tf.as_dtype(self.dtype or tf.keras.backend.floatx())
if not (dtype.is_floating or dtype.is_complex):
raise TypeError("Unable to build `Dense3D` layer with non-floating "
"point (and non-complex) dtype %s" % (dtype,))
input_shape = tf.TensorShape(input_shape)
if tf.compat.dimension_value(input_shape[-1]) is None:
raise ValueError("The last dimension of the inputs to `Dense3D` "
"should be defined. Found `None`.")
self.last_dim = tf.compat.dimension_value(input_shape[-1])
self.input_spec = tf.keras.layers.InputSpec(
min_ndim=3, axes={-1: self.last_dim})
# Determines variable shapes.
if self.backward_compatible:
kernel_shape = self.compatible_kernel_shape
bias_shape = self.compatible_bias_shape
else:
kernel_shape = self.kernel_shape
bias_shape = self.bias_shape
self.kernel = self.add_weight(
"kernel",
shape=kernel_shape,
initializer=self.kernel_initializer,
dtype=self.dtype,
trainable=True)
if self.use_bias:
self.bias = self.add_weight(
"bias",
shape=bias_shape,
initializer=self.bias_initializer,
dtype=self.dtype,
trainable=True)
else:
self.bias = None
super(Dense3D, self).build(input_shape)
def call(self, inputs):
"""Implements ``call()`` for Dense3D.
Args:
inputs: A float tensor of shape [batch_size, sequence_length, hidden_size]
when output_projection is False, otherwise a float tensor of shape
[batch_size, sequence_length, num_heads, dim_per_head].
Returns:
The projected tensor with shape [batch_size, sequence_length, num_heads,
dim_per_head] when output_projection is False, otherwise [batch_size,
sequence_length, hidden_size].
"""
if self.backward_compatible:
kernel = tf.keras.backend.reshape(self.kernel, self.kernel_shape)
bias = (
tf.keras.backend.reshape(self.bias, self.bias_shape)
if self.use_bias else None)
else:
kernel = self.kernel
bias = self.bias
if self.output_projection:
ret = tf.einsum("abcd,cde->abe", inputs, kernel)
else:
ret = tf.einsum("abc,cde->abde", inputs, kernel)
if self.use_bias:
ret += bias
if self.activation is not None:
return self.activation(ret)
return ret
class Dense2DProjection(tf.keras.layers.Layer):
"""A 2D projection layer with tf.einsum implementation."""
def __init__(self,
output_size,
kernel_initializer=None,
bias_initializer="zeros",
activation=None,
fp32_activation=False,
**kwargs):
super(Dense2DProjection, self).__init__(**kwargs)
self.output_size = output_size
self.kernel_initializer = kernel_initializer
self.bias_initializer = bias_initializer
self.activation = activation
self.fp32_activation = fp32_activation
def build(self, input_shape):
"""Implements build() for the layer."""
dtype = tf.as_dtype(self.dtype or tf.keras.backend.floatx())
if not (dtype.is_floating or dtype.is_complex):
raise TypeError("Unable to build `Dense2DProjection` layer with "
"non-floating point (and non-complex) "
"dtype %s" % (dtype,))
input_shape = tf.TensorShape(input_shape)
if tf.compat.dimension_value(input_shape[-1]) is None:
raise ValueError("The last dimension of the inputs to "
"`Dense2DProjection` should be defined. "
"Found `None`.")
last_dim = tf.compat.dimension_value(input_shape[-1])
self.input_spec = tf.keras.layers.InputSpec(min_ndim=3, axes={-1: last_dim})
self.kernel = self.add_weight(
"kernel",
shape=[last_dim, self.output_size],
initializer=self.kernel_initializer,
dtype=self.dtype,
trainable=True)
self.bias = self.add_weight(
"bias",
shape=[self.output_size],
initializer=self.bias_initializer,
dtype=self.dtype,
trainable=True)
super(Dense2DProjection, self).build(input_shape)
def call(self, inputs):
"""Implements call() for Dense2DProjection.
Args:
inputs: float Tensor of shape [batch, from_seq_length,
num_attention_heads, size_per_head].
Returns:
A 3D Tensor.
"""
ret = tf.einsum("abc,cd->abd", inputs, self.kernel)
ret += self.bias
if self.activation is not None:
if self.dtype == tf.float16 and self.fp32_activation:
ret = tf.cast(ret, tf.float32)
return self.activation(ret)
return ret
class TransformerBlock(tf.keras.layers.Layer):
"""Single transformer layer.
It has two sub-layers. The first is a multi-head self-attention mechanism, and
the second is a positionwise fully connected feed-forward network.
"""
def __init__(self,
hidden_size=768,
num_attention_heads=12,
intermediate_size=3072,
intermediate_activation="gelu",
hidden_dropout_prob=0.0,
attention_probs_dropout_prob=0.0,
initializer_range=0.02,
backward_compatible=False,
float_type=tf.float32,
**kwargs):
super(TransformerBlock, self).__init__(**kwargs)
self.hidden_size = hidden_size
self.num_attention_heads = num_attention_heads
self.intermediate_size = intermediate_size
self.intermediate_activation = tf_utils.get_activation(
intermediate_activation)
self.hidden_dropout_prob = hidden_dropout_prob
self.attention_probs_dropout_prob = attention_probs_dropout_prob
self.initializer_range = initializer_range
self.backward_compatible = backward_compatible
self.float_type = float_type
if self.hidden_size % self.num_attention_heads != 0:
raise ValueError(
"The hidden size (%d) is not a multiple of the number of attention "
"heads (%d)" % (self.hidden_size, self.num_attention_heads))
self.attention_head_size = int(self.hidden_size / self.num_attention_heads)
def build(self, unused_input_shapes):
"""Implements build() for the layer."""
self.attention_layer = Attention(
num_attention_heads=self.num_attention_heads,
size_per_head=self.attention_head_size,
attention_probs_dropout_prob=self.attention_probs_dropout_prob,
initializer_range=self.initializer_range,
backward_compatible=self.backward_compatible,
name="self_attention")
self.attention_output_dense = Dense3D(
num_attention_heads=self.num_attention_heads,
size_per_head=int(self.hidden_size / self.num_attention_heads),
kernel_initializer=get_initializer(self.initializer_range),
output_projection=True,
backward_compatible=self.backward_compatible,
name="self_attention_output")
self.attention_dropout = tf.keras.layers.Dropout(
rate=self.hidden_dropout_prob)
self.attention_layer_norm = (
tf.keras.layers.LayerNormalization(
name="self_attention_layer_norm",
axis=-1,
epsilon=1e-12,
# We do layer norm in float32 for numeric stability.
dtype=tf.float32))
self.intermediate_dense = Dense2DProjection(
output_size=self.intermediate_size,
kernel_initializer=get_initializer(self.initializer_range),
activation=self.intermediate_activation,
# Uses float32 so that gelu activation is done in float32.
fp32_activation=True,
name="intermediate")
self.output_dense = Dense2DProjection(
output_size=self.hidden_size,
kernel_initializer=get_initializer(self.initializer_range),
name="output")
self.output_dropout = tf.keras.layers.Dropout(rate=self.hidden_dropout_prob)
self.output_layer_norm = tf.keras.layers.LayerNormalization(
name="output_layer_norm", axis=-1, epsilon=1e-12, dtype=tf.float32)
super(TransformerBlock, self).build(unused_input_shapes)
def common_layers(self):
"""Explicitly gets all layer objects inside a Transformer encoder block."""
return [
self.attention_layer, self.attention_output_dense,
self.attention_dropout, self.attention_layer_norm,
self.intermediate_dense, self.output_dense, self.output_dropout,
self.output_layer_norm
]
def __call__(self, input_tensor, attention_mask=None, **kwargs):
inputs = tf_utils.pack_inputs([input_tensor, attention_mask])
return super(TransformerBlock, self).__call__(inputs, **kwargs)
def call(self, inputs):
"""Implements call() for the layer."""
(input_tensor, attention_mask) = tf_utils.unpack_inputs(inputs)
attention_output = self.attention_layer(
from_tensor=input_tensor,
to_tensor=input_tensor,
attention_mask=attention_mask)
attention_output = self.attention_output_dense(attention_output)
attention_output = self.attention_dropout(attention_output)
# Use float32 in keras layer norm and the gelu activation in the
# intermediate dense layer for numeric stability
attention_output = self.attention_layer_norm(input_tensor +
attention_output)
if self.float_type == tf.float16:
attention_output = tf.cast(attention_output, tf.float16)
intermediate_output = self.intermediate_dense(attention_output)
if self.float_type == tf.float16:
intermediate_output = tf.cast(intermediate_output, tf.float16)
layer_output = self.output_dense(intermediate_output)
layer_output = self.output_dropout(layer_output)
# Use float32 in keras layer norm for numeric stability
layer_output = self.output_layer_norm(layer_output + attention_output)
if self.float_type == tf.float16:
layer_output = tf.cast(layer_output, tf.float16)
return layer_output
class Transformer(tf.keras.layers.Layer):
"""Multi-headed, multi-layer Transformer from "Attention is All You Need".
This is almost an exact implementation of the original Transformer encoder.
See the original paper:
https://arxiv.org/abs/1706.03762
Also see:
https://github.com/tensorflow/tensor2tensor/blob/master/tensor2tensor/models/transformer.py
"""
def __init__(self,
num_hidden_layers=12,
hidden_size=768,
num_attention_heads=12,
intermediate_size=3072,
intermediate_activation="gelu",
hidden_dropout_prob=0.0,
attention_probs_dropout_prob=0.0,
initializer_range=0.02,
backward_compatible=False,
float_type=tf.float32,
**kwargs):
super(Transformer, self).__init__(**kwargs)
self.num_hidden_layers = num_hidden_layers
self.hidden_size = hidden_size
self.num_attention_heads = num_attention_heads
self.intermediate_size = intermediate_size
self.intermediate_activation = tf_utils.get_activation(
intermediate_activation)
self.hidden_dropout_prob = hidden_dropout_prob
self.attention_probs_dropout_prob = attention_probs_dropout_prob
self.initializer_range = initializer_range
self.backward_compatible = backward_compatible
self.float_type = float_type
def build(self, unused_input_shapes):
"""Implements build() for the layer."""
self.layers = []
for i in range(self.num_hidden_layers):
self.layers.append(
TransformerBlock(
hidden_size=self.hidden_size,
num_attention_heads=self.num_attention_heads,
intermediate_size=self.intermediate_size,
intermediate_activation=self.intermediate_activation,
hidden_dropout_prob=self.hidden_dropout_prob,
attention_probs_dropout_prob=self.attention_probs_dropout_prob,
initializer_range=self.initializer_range,
backward_compatible=self.backward_compatible,
float_type=self.float_type,
name=("layer_%d" % i)))
super(Transformer, self).build(unused_input_shapes)
def __call__(self, input_tensor, attention_mask=None, **kwargs):
inputs = tf_utils.pack_inputs([input_tensor, attention_mask])
return super(Transformer, self).__call__(inputs=inputs, **kwargs)
def call(self, inputs, return_all_layers=False):
"""Implements call() for the layer.
Args:
inputs: packed inputs.
return_all_layers: bool, whether to return outputs of all layers inside
encoders.
Returns:
Output tensor of the last layer or a list of output tensors.
"""
unpacked_inputs = tf_utils.unpack_inputs(inputs)
input_tensor = unpacked_inputs[0]
attention_mask = unpacked_inputs[1]
output_tensor = input_tensor
all_layer_outputs = []
for layer in self.layers:
output_tensor = layer(output_tensor, attention_mask)
all_layer_outputs.append(output_tensor)
if return_all_layers:
return all_layer_outputs
return all_layer_outputs[-1]
def get_initializer(initializer_range=0.02):
"""Creates a `tf.initializers.truncated_normal` with the given range.
Args:
initializer_range: float, initializer range for stddev.
Returns:
TruncatedNormal initializer with stddev = `initializer_range`.
"""
return tf.keras.initializers.TruncatedNormal(stddev=initializer_range)
def create_attention_mask_from_input_mask(from_tensor, to_mask):
"""Create 3D attention mask from a 2D tensor mask.
Args:
from_tensor: 2D or 3D Tensor of shape [batch_size, from_seq_length, ...].
to_mask: int32 Tensor of shape [batch_size, to_seq_length].
Returns:
float Tensor of shape [batch_size, from_seq_length, to_seq_length].
"""
from_shape = tf_utils.get_shape_list(from_tensor, expected_rank=[2, 3])
batch_size = from_shape[0]
from_seq_length = from_shape[1]
to_shape = tf_utils.get_shape_list(to_mask, expected_rank=2)
to_seq_length = to_shape[1]
to_mask = tf.cast(
tf.reshape(to_mask, [batch_size, 1, to_seq_length]),
dtype=from_tensor.dtype)
# We don't assume that `from_tensor` is a mask (although it could be). We
# don't actually care if we attend *from* padding tokens (only *to* padding)
# tokens so we create a tensor of all ones.
#
# `broadcast_ones` = [batch_size, from_seq_length, 1]
broadcast_ones = tf.ones(
shape=[batch_size, from_seq_length, 1], dtype=from_tensor.dtype)
# Here we broadcast along two dimensions to create the mask.
mask = broadcast_ones * to_mask
return mask
official/nlp/transformer/attention_layer.py
View file @ e5f021ce
...@@ -19,7 +19,7 @@ from __future__ import division ...@@ -19,7 +19,7 @@ from __future__ import division
from __future__ import print_function from __future__ import print_function
import tensorflow as tf import tensorflow as tf
from official.nlp import bert_modeling as common_layer from official.nlp.modeling import layers
class Attention(tf.keras.layers.Layer): class Attention(tf.keras.layers.Layer):
...@@ -47,18 +47,27 @@ class Attention(tf.keras.layers.Layer): ...@@ -47,18 +47,27 @@ class Attention(tf.keras.layers.Layer):
"""Builds the layer.""" """Builds the layer."""
# Layers for linearly projecting the queries, keys, and values. # Layers for linearly projecting the queries, keys, and values.
size_per_head = self.hidden_size // self.num_heads size_per_head = self.hidden_size // self.num_heads
self.query_dense_layer = common_layer.Dense3D( self.query_dense_layer = layers.DenseEinsum(
self.num_heads, size_per_head, kernel_initializer="glorot_uniform", output_shape=(self.num_heads, size_per_head),
use_bias=False, name="query") kernel_initializer="glorot_uniform",
self.key_dense_layer = common_layer.Dense3D( use_bias=False,
self.num_heads, size_per_head, kernel_initializer="glorot_uniform", name="query")
use_bias=False, name="key") self.key_dense_layer = layers.DenseEinsum(
self.value_dense_layer = common_layer.Dense3D( output_shape=(self.num_heads, size_per_head),
self.num_heads, size_per_head, kernel_initializer="glorot_uniform", kernel_initializer="glorot_uniform",
use_bias=False, name="value") use_bias=False,
self.output_dense_layer = common_layer.Dense3D( name="key")
self.num_heads, size_per_head, kernel_initializer="glorot_uniform", self.value_dense_layer = layers.DenseEinsum(
use_bias=False, output_projection=True, name="output_transform") output_shape=(self.num_heads, size_per_head),
kernel_initializer="glorot_uniform",
use_bias=False,
name="value")
self.output_dense_layer = layers.DenseEinsum(
output_shape=self.hidden_size,
num_summed_dimensions=2,
kernel_initializer="glorot_uniform",
use_bias=False,
name="output_transform")
super(Attention, self).build(input_shape) super(Attention, self).build(input_shape)
def get_config(self): def get_config(self):
......
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