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paddlepaddle--paddle/python/paddle/io/dataloader/batch_sampler.py
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2026-07-13 12:40:42 +08:00

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# Copyright (c) 2020 PaddlePaddle 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.
from __future__ import annotations
import math
from collections.abc import Iterable, Iterator, Sequence, Sized
from typing import overload
import numpy as np
from paddle.utils.decorator_utils import batch_sampler_decorator
from .dataset import IterableDataset
from .sampler import RandomSampler, Sampler, SequenceSampler
class BatchSampler(Sampler[Sequence[int]]):
"""
A base implement of batch sampler used by `paddle.io.DataLoader`
which yield mini-batch indices(a list/tuple with length as
mini-batch size and holds sample indices) iterably.
Batch sampler used by :code:`paddle.io.DataLoader` should be a subclass
of :code:`paddle.io.BatchSampler`, BatchSampler subclasses should
implement following methods:
:code:`__iter__`: return mini-batch indices iterably.
:code:`__len__`: get mini-batch number in an epoch.
Args:
dataset(Dataset, optional): this should be an instance of a subclass of :ref:`api_paddle_io_Dataset` or
:ref:`api_paddle_io_IterableDataset` or other python object which implemented
:code:`__len__` for BatchSampler to get indices as the
range of :attr:`dataset` length. Default None, disabled.
sampler (Sampler, Iterable, optional): this should be a :ref:`api_paddle_io_Sample` or Iterable
instance which implemented :code:`__iter__` to generate
sample indices. :attr:`sampler` and :attr:`dataset`
can not be set in the same time. If :attr:`sampler`
is set, :attr:`dataset` should not be set. Default None, disabled.
shuffle(bool, optional): whether to shuffle indices order before generating
batch indices. Default False, don't shuffle indices before generating batch indices.
batch_size(int, optional): sample indice number in a mini-batch indices. default 1, each mini-batch includes 1 sample.
drop_last(bool, optional): whether drop the last incomplete (less than 1 mini-batch) batch dataset. Default False, keep it.
see :ref:`api_paddle_io_DataLoader`
Returns:
BatchSampler: an iterable object for indices iterating
Examples:
.. code-block:: pycon
>>> import numpy as np
>>> from paddle.io import RandomSampler, BatchSampler, Dataset
>>> np.random.seed(2023)
>>> # init with dataset
>>> class RandomDataset(Dataset): # type: ignore[type-arg]
... def __init__(self, num_samples):
... self.num_samples = num_samples
...
... def __getitem__(self, idx):
... image = np.random.random([784]).astype('float32')
... label = np.random.randint(0, 9, (1,)).astype('int64')
... return image, label
...
... def __len__(self):
... return self.num_samples
>>> bs = BatchSampler(
... dataset=RandomDataset(100),
... shuffle=False,
... batch_size=16,
... drop_last=False,
... )
>>> for batch_indices in bs:
... print(batch_indices)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
...
[96, 97, 98, 99]
>>> # init with sampler
>>> sampler = RandomSampler(RandomDataset(100))
>>> bs = BatchSampler(
... sampler=sampler,
... batch_size=8,
... drop_last=True,
... )
>>> for batch_indices in bs:
... print(batch_indices)
[56, 12, 68, 0, 82, 66, 91, 44]
...
[53, 17, 22, 86, 52, 3, 92, 33]
"""
sampler: Sampler[int] | Iterable[int]
batch_size: int
shuffle: bool
drop_last: bool
@overload
def __init__(
self,
dataset: Sized | None = None,
sampler: Sampler | Iterable[int] | None = None,
shuffle: bool = False,
batch_size: int = 1,
drop_last: bool = False,
) -> None: ...
@overload
def __init__(
self,
sampler: Sampler | Iterable[int] | None = None,
batch_size: int = 1,
drop_last: bool = False,
) -> None: ...
@batch_sampler_decorator
def __init__(
self,
dataset: Sized | None = None,
sampler: Sampler | Iterable[int] | None = None,
shuffle: bool = False,
batch_size: int = 1,
drop_last: bool = False,
) -> None:
if dataset is None:
assert sampler is not None, (
"either dataset or sampler should be set"
)
assert isinstance(sampler, (Sampler, Iterable)), (
f"sampler should be either paddle.io.Sampler or Iterable, but got {type(sampler)}"
)
assert not shuffle, "shuffle should be False when sampler is set"
self.sampler = sampler
else:
assert not isinstance(dataset, IterableDataset), (
"dataset should not be a paddle.io.IterableDataset"
)
assert sampler is None, "should not set both dataset and sampler"
assert isinstance(shuffle, bool), (
f"shuffle should be a boolean value, but got {type(shuffle)}"
)
if shuffle:
self.sampler = RandomSampler(dataset)
else:
self.sampler = SequenceSampler(dataset)
assert isinstance(batch_size, int) and batch_size > 0, (
f"batch_size should be a positive integer, but got {batch_size}"
)
self.batch_size = batch_size # per_device_batch_size or mini_batch_size
self.shuffle = shuffle
assert isinstance(drop_last, bool), (
f"drop_last should be a boolean value, but got {type(drop_last)}"
)
self.drop_last = drop_last
# TODO(dev): consider to make it as public argument, acc_steps is only used
# in auto-parallel
self._acc_steps = 1
def __iter__(self) -> Iterator[list[int]]:
local_batch_size = self.batch_size * self._acc_steps
batch_indices = []
for idx in self.sampler:
batch_indices.append(idx)
if len(batch_indices) == local_batch_size:
yield batch_indices
batch_indices = []
if not self.drop_last and len(batch_indices) > 0:
yield batch_indices
def __len__(self) -> int:
local_batch_size = self.batch_size * self._acc_steps
num_samples = len(self.sampler)
num_samples += int(not self.drop_last) * (local_batch_size - 1)
return num_samples // local_batch_size
class _InfiniteIterableSampler(Sampler[Sequence[None]]):
dataset: IterableDataset
batch_size: int
def __init__(self, dataset: IterableDataset, batch_size: int = 1) -> None:
assert isinstance(dataset, IterableDataset), (
"dataset should be an instance of paddle.io.IterableDataset"
)
self.dataset = dataset
self.batch_size = batch_size
def __iter__(self) -> Iterator[list[None]]:
while True:
yield [None] * self.batch_size
class DistributedBatchSampler(BatchSampler):
"""Sampler that restricts data loading to a subset of the dataset.
In such case, each process can pass a DistributedBatchSampler instance
as a DataLoader sampler, and load a subset of the original dataset that
is exclusive to it.
.. note::
Dataset is assumed to be of constant size.
Args:
dataset(Dataset): this could be an instance of subclass of :ref:`api_paddle_io_Dataset`
or other python object which implemented
`__len__` for BatchSampler to get indices of samples.
batch_size(int): sample size of each mini-batch.
num_replicas(int, optional): process number in distributed training.
If :attr:`num_replicas` is None, :attr:`num_replicas` will be
retrieved from :ref:`api_paddle_distributed_ParallelEnv` .
Default None.
rank(int, optional): the rank of the current process among :attr:`num_replicas`
processes. If :attr:`rank` is None, :attr:`rank` is retrieved from
:ref:`api_paddle_distributed_ParallelEnv`. Default None.
shuffle(bool, optional): whether to shuffle indices order before generating
batch indices. Default False.
drop_last(bool, optional): whether drop the last incomplete(less than a mini-batch) batch dataset size.
Default False.
seed(int, optional): random seed used to shuffle indices order if
:attr:`shuffle=True`. This number should be identical across all
processes in the distributed group. Default 0.
Returns:
DistributedBatchSampler, return an iterable object for indices iterating.
Examples:
.. code-block:: pycon
>>> import numpy as np
>>> from paddle.io import Dataset, DistributedBatchSampler
>>> # init with dataset
>>> class RandomDataset(Dataset): # type: ignore[type-arg]
... def __init__(self, num_samples):
... self.num_samples = num_samples
...
... def __getitem__(self, idx):
... image = np.random.random([784]).astype('float32')
... label = np.random.randint(0, 9, (1,)).astype('int64')
... return image, label
...
... def __len__(self):
... return self.num_samples
>>> dataset = RandomDataset(100)
>>> sampler = DistributedBatchSampler(dataset, batch_size=64)
>>> for data in sampler:
... # do something
... break
"""
dataset: Sized
batch_size: int
drop_last: bool
nranks: int
epoch: int
local_rank: int
num_samples: int
total_size: int
def __init__(
self,
dataset: Sized,
batch_size: int,
num_replicas: int | None = None,
rank: int | None = None,
shuffle: bool = False,
drop_last: bool = False,
seed: int = 0,
) -> None:
self.dataset = dataset
assert isinstance(batch_size, int) and batch_size > 0, (
"batch_size should be a positive integer"
)
self.batch_size = batch_size
assert isinstance(shuffle, bool), "shuffle should be a boolean value"
self.shuffle = shuffle
assert isinstance(drop_last, bool), (
"drop_last should be a boolean number"
)
from paddle.distributed import ParallelEnv
if num_replicas is not None:
assert isinstance(num_replicas, int) and num_replicas > 0, (
"num_replicas should be a positive integer"
)
self.nranks = num_replicas
else:
self.nranks = ParallelEnv().nranks
if rank is not None:
assert isinstance(rank, int) and rank >= 0, (
"rank should be a non-negative integer"
)
self.local_rank = rank
else:
self.local_rank = ParallelEnv().local_rank
self.drop_last = drop_last
self.epoch = 0
self.num_samples = int(math.ceil(len(self.dataset) * 1.0 / self.nranks))
self.total_size = self.num_samples * self.nranks
self.seed = seed
# TODO(dev): consider to make it as public argument, acc_steps is only used
# in auto-parallel
self._acc_steps = 1
def __iter__(self) -> Iterator[list[int]]:
local_batch_size = self.batch_size * self._acc_steps
num_samples = len(self.dataset)
indices = np.arange(num_samples).tolist()
# add extra samples to make it evenly divisible
padding_size = self.total_size - len(indices)
if padding_size <= len(indices):
indices += indices[:padding_size]
else:
indices += (indices * math.ceil(padding_size / len(indices)))[
:padding_size
]
assert len(indices) == self.total_size
if self.shuffle:
np.random.RandomState(self.seed + self.epoch).shuffle(indices)
self.epoch += 1
# subsample
def _get_indices_by_batch_size(indices):
subsampled_indices = []
last_batch_size = self.total_size % (self.batch_size * self.nranks)
assert last_batch_size % self.nranks == 0
last_local_batch_size = last_batch_size // self.nranks
for i in range(
self.local_rank * self.batch_size,
len(indices) - last_batch_size,
self.batch_size * self.nranks,
):
subsampled_indices.extend(indices[i : i + self.batch_size])
indices = indices[len(indices) - last_batch_size :]
subsampled_indices.extend(
indices[
self.local_rank * last_local_batch_size : (
self.local_rank + 1
)
* last_local_batch_size
]
)
return subsampled_indices
if self.nranks > 1:
indices = _get_indices_by_batch_size(indices)
assert len(indices) == self.num_samples
_sample_iter = iter(indices)
batch_indices = []
for idx in _sample_iter:
batch_indices.append(idx)
if len(batch_indices) == local_batch_size:
yield batch_indices
batch_indices = []
if not self.drop_last and len(batch_indices) > 0:
yield batch_indices
def __len__(self) -> int:
local_batch_size = self.batch_size * self._acc_steps
num_samples = self.num_samples
num_samples += int(not self.drop_last) * (local_batch_size - 1)
return num_samples // local_batch_size
def set_epoch(self, epoch: int) -> None:
"""
Sets the epoch number. When :attr:`shuffle=True`, this number is used
as seeds of random numbers. By default, users may not set this, all
replicas (workers) use a different random ordering for each epoch.
If set same number at each epoch, this sampler will yield the same
ordering at all epochs.
Arguments:
epoch (int): Epoch number.
Examples:
.. code-block:: pycon
>>> import numpy as np
>>> from paddle.io import Dataset, DistributedBatchSampler
>>> # init with dataset
>>> class RandomDataset(Dataset): # type: ignore[type-arg]
... def __init__(self, num_samples):
... self.num_samples = num_samples
...
... def __getitem__(self, idx):
... image = np.random.random([784]).astype('float32')
... label = np.random.randint(0, 9, (1,)).astype('int64')
... return image, label
...
... def __len__(self):
... return self.num_samples
>>> dataset = RandomDataset(100)
>>> sampler = DistributedBatchSampler(dataset, batch_size=64)
>>> for epoch in range(10):
... sampler.set_epoch(epoch)
"""
self.epoch = epoch