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# Copyright 2020 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.
# ==============================================================================
"""Input pipelines."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import tensorflow.compat.v2 as tf
def decode_record(record, name_to_features):
"""Decodes a record to a TensorFlow example."""
example = tf.io.parse_single_example(record, name_to_features)
# tf.Example only supports tf.int64, but the TPU only supports tf.int32.
# So cast all int64 to int32.
for name in list(example.keys()):
t = example[name]
if t.dtype == tf.int64:
t = tf.cast(t, tf.int32)
example[name] = t
return example
def process_singledoc_dataset(dataset, batch_size, params):
"""Parses and batches single-doc dataset."""
name_to_features = {
"input_ids_a": tf.io.FixedLenFeature([params.len_title], tf.int64),
"input_ids_b": tf.io.FixedLenFeature([params.len_passage], tf.int64),
"input_mask_b": tf.io.FixedLenFeature([params.len_passage], tf.int64),
"segment_ids_b": tf.io.FixedLenFeature([params.len_passage], tf.int64),
}
decode_fn = lambda record: decode_record(record, name_to_features)
dataset = dataset.map(
decode_fn, num_parallel_calls=tf.data.experimental.AUTOTUNE)
def _select_data_from_record(record):
"""Filter out features to use for pretraining."""
return {
"input_ids": record["input_ids_b"],
"input_mask": record["input_mask_b"],
"segment_ids": record["segment_ids_b"],
"target_ids": record["input_ids_a"],
}
dataset = dataset.map(
_select_data_from_record,
num_parallel_calls=tf.data.experimental.AUTOTUNE)
dataset = dataset.batch(batch_size, drop_remainder=True)
return dataset
def decode_sparse_record(record, name_to_features):
"""Decodes a sparse record to a TensorFlow example."""
example = tf.io.parse_single_example(record, name_to_features)
# tf.Example only supports tf.int64, but the TPU only supports tf.int32.
# So cast all int64 to int32.
for name in list(example.keys()):
t = example[name]
if t.dtype == tf.int64:
t = tf.cast(t, tf.int32)
example[name] = tf.sparse.to_dense(t)
return example
def _filter_max_length(example, max_title_length=256):
"""Indicates whether the example's length is lower than the maximum length."""
return tf.size(example["targets"]) <= max_title_length
def process_singledoc_transformer_dataset(dataset, batch_size, params):
"""Parses, batches and pads single-doc dataset."""
name_to_features = {
"inputs": tf.io.VarLenFeature(tf.int64),
"targets": tf.io.VarLenFeature(tf.int64),
}
decode_fn = lambda record: decode_sparse_record(record, name_to_features)
dataset = dataset.map(
decode_fn, num_parallel_calls=tf.data.experimental.AUTOTUNE)
def _select_data_from_record(record):
"""Filter out features to use for pretraining."""
input_ids = record["inputs"][:params.len_passage]
target_ids = record["targets"]
input_mask = tf.ones_like(input_ids)
segment_ids = tf.zeros_like(input_ids)
return {
"input_ids": input_ids,
"input_mask": input_mask,
"segment_ids": segment_ids,
"target_ids": target_ids,
}
dataset = dataset.filter(lambda x: _filter_max_length(x, params.len_title))
dataset = dataset.map(
_select_data_from_record,
num_parallel_calls=tf.data.experimental.AUTOTUNE)
dataset = dataset.padded_batch(
batch_size, {
"input_ids": [params.len_passage],
"input_mask": [params.len_passage],
"segment_ids": [params.len_passage],
"target_ids": [params.len_title],
},
padding_values={
"input_ids": params.pad_token_id,
"input_mask": 0,
"segment_ids": 0,
"target_ids": params.pad_token_id,
},
drop_remainder=True)
return dataset
def multidoc_parse_spec(params, training=True):
"""Gets the mutli-doc tf.Example parsing spec."""
len_p = params.len_passage
name_to_features = {}
feature_list = ["input_ids", "input_mask", "segment_ids"]
for idx in params.passage_list:
for feature in feature_list:
name_to_features["%s_%s" % (feature, idx)] = tf.io.FixedLenFeature(
[len_p], tf.int64)
if training:
# Cluster title.
name_to_features["input_ids_a"] = tf.io.FixedLenFeature([params.len_title],
tf.int64)
return name_to_features, feature_list
def process_multidoc_dataset(dataset, batch_size, params):
"""Parses, organizes and batches multi-doc dataset."""
name_to_features, feature_list = multidoc_parse_spec(params)
decode_fn = lambda record: decode_record(record, name_to_features)
dataset = dataset.map(
decode_fn, num_parallel_calls=tf.data.experimental.AUTOTUNE)
def _select_data_from_record(record):
"""Filter out features to use for pretraining."""
features = {"target_ids": record["input_ids_a"]}
for feature in feature_list:
tensors = [record["%s_%s" % (feature, i)] for i in params.passage_list]
features[feature] = tf.stack(tensors)
return features
dataset = dataset.map(
_select_data_from_record,
num_parallel_calls=tf.data.experimental.AUTOTUNE)
dataset = dataset.batch(batch_size, drop_remainder=True)
return dataset
def create_dataset(file_paths,
batch_size,
params,
is_training=True,
input_pipeline_context=None):
"""Creates input dataset from (tf)records files for pretraining."""
dataset = tf.data.Dataset.list_files(file_paths, shuffle=is_training)
if input_pipeline_context and input_pipeline_context.num_input_pipelines > 1:
if not is_training or params.input_sharding:
dataset = dataset.shard(input_pipeline_context.num_input_pipelines,
input_pipeline_context.input_pipeline_id)
if is_training:
dataset = dataset.repeat()
# We set shuffle buffer to exactly match total number of
# training files to ensure that training data is well shuffled.
dataset = dataset.shuffle(len(file_paths))
# In parallel, create tf record dataset for each train files.
# cycle_length = 8 means that up to 8 files will be read and deserialized in
# parallel. You may want to increase this number if you have a large number of
# CPU cores.
dataset = dataset.interleave(
tf.data.TFRecordDataset,
cycle_length=8,
num_parallel_calls=tf.data.experimental.AUTOTUNE)
if is_training:
dataset = dataset.shuffle(100)
if params.get("multi_channel_cross_attention", value=False):
dataset = process_multidoc_dataset(dataset, batch_size, params)
else:
if not params.input_data_not_padded:
dataset = process_singledoc_dataset(dataset, batch_size, params)
else:
dataset = process_singledoc_transformer_dataset(dataset, batch_size,
params)
dataset = dataset.prefetch(tf.data.experimental.AUTOTUNE)
return dataset
def get_input_dataset(input_file_pattern,
batch_size,
params,
is_training,
strategy=None):
"""Returns input dataset from input file string."""
# When using TPU pods, we need to clone dataset across
# workers and need to pass in function that returns the dataset rather
# than passing dataset instance itself.
use_dataset_fn = isinstance(strategy, tf.distribute.experimental.TPUStrategy)
if use_dataset_fn:
if batch_size % strategy.num_replicas_in_sync != 0:
raise ValueError(
"Batch size must be divisible by number of replicas : {}".format(
strategy.num_replicas_in_sync))
# As auto rebatching is not supported in
# `experimental_distribute_datasets_from_function()` API, which is
# required when cloning dataset to multiple workers in eager mode,
# we use per-replica batch size.
batch_size = int(batch_size / strategy.num_replicas_in_sync)
def _dataset_fn(ctx=None):
"""Returns tf.data.Dataset for distributed BERT pretraining."""
input_files = []
for input_pattern in input_file_pattern.split(","):
input_files.extend(tf.io.gfile.glob(input_pattern))
return create_dataset(
input_files,
batch_size,
params,
is_training=is_training,
input_pipeline_context=ctx)
if use_dataset_fn:
return strategy.experimental_distribute_datasets_from_function(_dataset_fn)
else:
return strategy.experimental_distribute_dataset(_dataset_fn())
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