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# Licensed under the Apache License, Version 2.0 (the "License");
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from __future__ import division, print_function
import math
import paddle
__all__ = ["DistributedBatchSampler"]
[docs]class DistributedBatchSampler(paddle.io.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(paddle.io.Dataset): this could be a `paddle.io.Dataset` implement
or other python object which implemented
`__len__` for BatchSampler to get sample
number of data source.
batch_size(int): sample indice number in a mini-batch indices.
num_replicas(int, optional): porcess number in distributed training.
If :attr:`num_replicas` is None, :attr:`num_replicas` will be
retrieved from :code:`paddle.distributed.ParallenEnv`.
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
:code:`paddle.distributed.ParallenEnv`. Default None.
shuffle(bool): whther to shuffle indices order before genrating
batch indices. Default False.
drop_last(bool): whether drop the last incomplete batch dataset size
is not divisible by the batch size. Default False
Examples:
.. code-block:: python
import numpy as np
from paddle.io import Dataset, DistributedBatchSampler
# init with dataset
class RandomDataset(Dataset):
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
"""
def __init__(
self, dataset, batch_size, num_replicas=None, rank=None, shuffle=False, drop_last=False, consumed_samples=0
):
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.consumed_samples = consumed_samples
if self.dataset is None:
# In pre-training mode when using distributed dataloader, the input dataset can be None. We should handle this situation.
self.num_samples = 0
else:
self.num_samples = int(math.ceil(len(self.dataset) * 1.0 / self.nranks))
self.total_size = self.num_samples * self.nranks
def get_start_end_idx(self):
start_idx = self.local_rank * self.batch_size
end_idx = start_idx + self.batch_size
return start_idx, end_idx
def __iter__(self):
assert (
self.consumed_samples % self.nranks == 0
), "The consumed_samples should be divided by nranks. consumed_samples=%d, nranks=%s" % (
self.consumed_samples,
self.nranks,
)
self.remain_num_samples = int(math.ceil((len(self.dataset) - self.consumed_samples) * 1.0 / self.nranks))
self.remain_total_size = self.remain_num_samples * self.nranks
self.batch_size_times_rank_size = self.batch_size * self.nranks
batch_indices = []
for idx in range(self.consumed_samples, self.total_size):
batch_indices.append(idx)
if len(batch_indices) == self.batch_size_times_rank_size:
start_idx, end_idx = self.get_start_end_idx()
yield batch_indices[start_idx:end_idx]
batch_indices = []
if not self.drop_last and len(batch_indices) > 0:
yield batch_indices
def __len__(self):
num_samples = self.num_samples
num_samples += int(not self.drop_last) * (self.batch_size - 1)
return num_samples // self.batch_size
[docs] def set_epoch(self, epoch=0, consumed_samples=0):
"""
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 epoches.
Arguments:
epoch (int): Epoch number.
Examples:
.. code-block:: python
from paddle.io import Dataset, DistributedBatchSampler
# init with dataset
class RandomDataset(Dataset):
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
# if we reset the epoch, the consumed_samples should be set to 0.
self.consumed_samples = consumed_samples
