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# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
"""
This module contains collection of classes which implement
collate functionalities for various tasks.
Collaters should know what data to expect for each sample
and they should pack / collate them into batches
"""
from __future__ import absolute_import, division, print_function, unicode_literals
import numpy as np
import torch
from fairseq.data import data_utils as fairseq_data_utils
class Seq2SeqCollater(object):
"""
Implements collate function mainly for seq2seq tasks
This expects each sample to contain feature (src_tokens) and
targets.
This collator is also used for aligned training task.
"""
def __init__(
self,
feature_index=0,
label_index=1,
pad_index=1,
eos_index=2,
move_eos_to_beginning=True,
):
self.feature_index = feature_index
self.label_index = label_index
self.pad_index = pad_index
self.eos_index = eos_index
self.move_eos_to_beginning = move_eos_to_beginning
def _collate_frames(self, frames):
"""Convert a list of 2d frames into a padded 3d tensor
Args:
frames (list): list of 2d frames of size L[i]*f_dim. Where L[i] is
length of i-th frame and f_dim is static dimension of features
Returns:
3d tensor of size len(frames)*len_max*f_dim where len_max is max of L[i]
"""
len_max = max(frame.size(0) for frame in frames)
f_dim = frames[0].size(1)
res = frames[0].new(len(frames), len_max, f_dim).fill_(0.0)
for i, v in enumerate(frames):
res[i, : v.size(0)] = v
return res
def collate(self, samples):
"""
utility function to collate samples into batch for speech recognition.
"""
if len(samples) == 0:
return {}
# parse samples into torch tensors
parsed_samples = []
for s in samples:
# skip invalid samples
if s["data"][self.feature_index] is None:
continue
source = s["data"][self.feature_index]
if isinstance(source, (np.ndarray, np.generic)):
source = torch.from_numpy(source)
target = s["data"][self.label_index]
if isinstance(target, (np.ndarray, np.generic)):
target = torch.from_numpy(target).long()
elif isinstance(target, list):
target = torch.LongTensor(target)
parsed_sample = {"id": s["id"], "source": source, "target": target}
parsed_samples.append(parsed_sample)
samples = parsed_samples
id = torch.LongTensor([s["id"] for s in samples])
frames = self._collate_frames([s["source"] for s in samples])
# sort samples by descending number of frames
frames_lengths = torch.LongTensor([s["source"].size(0) for s in samples])
frames_lengths, sort_order = frames_lengths.sort(descending=True)
id = id.index_select(0, sort_order)
frames = frames.index_select(0, sort_order)
target = None
target_lengths = None
prev_output_tokens = None
if samples[0].get("target", None) is not None:
ntokens = sum(len(s["target"]) for s in samples)
target = fairseq_data_utils.collate_tokens(
[s["target"] for s in samples],
self.pad_index,
self.eos_index,
left_pad=False,
move_eos_to_beginning=False,
)
target = target.index_select(0, sort_order)
target_lengths = torch.LongTensor(
[s["target"].size(0) for s in samples]
).index_select(0, sort_order)
prev_output_tokens = fairseq_data_utils.collate_tokens(
[s["target"] for s in samples],
self.pad_index,
self.eos_index,
left_pad=False,
move_eos_to_beginning=self.move_eos_to_beginning,
)
prev_output_tokens = prev_output_tokens.index_select(0, sort_order)
else:
ntokens = sum(len(s["source"]) for s in samples)
batch = {
"id": id,
"ntokens": ntokens,
"net_input": {"src_tokens": frames, "src_lengths": frames_lengths},
"target": target,
"target_lengths": target_lengths,
"nsentences": len(samples),
}
if prev_output_tokens is not None:
batch["net_input"]["prev_output_tokens"] = prev_output_tokens
return batch
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