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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.
import bisect
import numpy as np
from torch.utils.data.dataloader import default_collate
from . import FairseqDataset
class ConcatDataset(FairseqDataset):
@staticmethod
def cumsum(sequence, sample_ratios):
r, s = [], 0
for e, ratio in zip(sequence, sample_ratios):
curr_len = int(ratio * len(e))
r.append(curr_len + s)
s += curr_len
return r
def __init__(self, datasets, sample_ratios=1):
super(ConcatDataset, self).__init__()
assert len(datasets) > 0, "datasets should not be an empty iterable"
self.datasets = list(datasets)
if isinstance(sample_ratios, int):
sample_ratios = [sample_ratios] * len(self.datasets)
self.sample_ratios = sample_ratios
self.cumulative_sizes = self.cumsum(self.datasets, sample_ratios)
self.real_sizes = [len(d) for d in self.datasets]
def __len__(self):
return self.cumulative_sizes[-1]
def __getitem__(self, idx):
dataset_idx, sample_idx = self._get_dataset_and_sample_index(idx)
return self.datasets[dataset_idx][sample_idx]
def _get_dataset_and_sample_index(self, idx: int):
dataset_idx = bisect.bisect_right(self.cumulative_sizes, idx)
if dataset_idx == 0:
sample_idx = idx
else:
sample_idx = idx - self.cumulative_sizes[dataset_idx - 1]
sample_idx = sample_idx % self.real_sizes[dataset_idx]
return dataset_idx, sample_idx
def collater(self, samples, **extra_args):
# For now only supports datasets with same underlying collater implementations
if hasattr(self.datasets[0], "collater"):
return self.datasets[0].collater(samples, **extra_args)
else:
return default_collate(samples, **extra_args)
def size(self, idx: int):
"""
Return an example's size as a float or tuple.
"""
dataset_idx, sample_idx = self._get_dataset_and_sample_index(idx)
return self.datasets[dataset_idx].size(sample_idx)
def num_tokens(self, index: int):
return np.max(self.size(index))
def attr(self, attr: str, index: int):
dataset_idx = bisect.bisect_right(self.cumulative_sizes, index)
return getattr(self.datasets[dataset_idx], attr, None)
@property
def sizes(self):
_dataset_sizes = []
for ds, sr in zip(self.datasets, self.sample_ratios):
if isinstance(ds.sizes, np.ndarray):
_dataset_sizes.append(np.tile(ds.sizes, sr))
else:
# Only support underlying dataset with single size array.
assert isinstance(ds.sizes, list)
_dataset_sizes.append(np.tile(ds.sizes[0], sr))
return np.concatenate(_dataset_sizes)
@property
def supports_prefetch(self):
return all(d.supports_prefetch for d in self.datasets)
def ordered_indices(self):
"""
Returns indices sorted by length. So less padding is needed.
"""
if isinstance(self.sizes, np.ndarray) and len(self.sizes.shape) > 1:
# special handling for concatenating lang_pair_datasets
indices = np.arange(len(self))
sizes = self.sizes
tgt_sizes = (
sizes[:, 1] if len(sizes.shape) > 0 and sizes.shape[1] > 1 else None
)
src_sizes = (
sizes[:, 0] if len(sizes.shape) > 0 and sizes.shape[1] > 1 else sizes
)
# sort by target length, then source length
if tgt_sizes is not None:
indices = indices[np.argsort(tgt_sizes[indices], kind="mergesort")]
return indices[np.argsort(src_sizes[indices], kind="mergesort")]
else:
return np.argsort(self.sizes)
def prefetch(self, indices):
frm = 0
for to, ds in zip(self.cumulative_sizes, self.datasets):
real_size = len(ds)
if getattr(ds, "supports_prefetch", False):
ds.prefetch([(i - frm) % real_size for i in indices if frm <= i < to])
frm = to
@property
def can_reuse_epoch_itr_across_epochs(self):
return all(d.can_reuse_epoch_itr_across_epochs for d in self.datasets)
def set_epoch(self, epoch):
super().set_epoch(epoch)
for ds in self.datasets:
if hasattr(ds, "set_epoch"):
ds.set_epoch(epoch)
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