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import math
import torch
from torch.utils.data import Sampler
import torch.distributed as dist
class OrderedDistributedSampler(Sampler):
"""Sampler that restricts data loading to a subset of the dataset.
It is especially useful in conjunction with
:class:`torch.nn.parallel.DistributedDataParallel`. In such case, each
process can pass a DistributedSampler 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.
Arguments:
dataset: Dataset used for sampling.
num_replicas (optional): Number of processes participating in
distributed training.
rank (optional): Rank of the current process within num_replicas.
"""
def __init__(self, dataset, num_replicas=None, rank=None):
if num_replicas is None:
if not dist.is_available():
raise RuntimeError("Requires distributed package to be available")
num_replicas = dist.get_world_size()
if rank is None:
if not dist.is_available():
raise RuntimeError("Requires distributed package to be available")
rank = dist.get_rank()
self.dataset = dataset
self.num_replicas = num_replicas
self.rank = rank
self.num_samples = int(math.ceil(len(self.dataset) * 1.0 / self.num_replicas))
self.total_size = self.num_samples * self.num_replicas
def __iter__(self):
indices = list(range(len(self.dataset)))
# add extra samples to make it evenly divisible
indices += indices[:(self.total_size - len(indices))]
assert len(indices) == self.total_size
# subsample
indices = indices[self.rank:self.total_size:self.num_replicas]
assert len(indices) == self.num_samples
return iter(indices)
def __len__(self):
return self.num_samples
class RepeatAugSampler(Sampler):
"""Sampler that restricts data loading to a subset of the dataset for distributed,
with repeated augmentation.
It ensures that different each augmented version of a sample will be visible to a
different process (GPU). Heavily based on torch.utils.data.DistributedSampler
This sampler was taken from https://github.com/facebookresearch/deit/blob/0c4b8f60/samplers.py
Used in
Copyright (c) 2015-present, Facebook, Inc.
"""
def __init__(
self,
dataset,
num_replicas=None,
rank=None,
shuffle=True,
num_repeats=3,
selected_round=256,
selected_ratio=0,
):
if num_replicas is None:
if not dist.is_available():
raise RuntimeError("Requires distributed package to be available")
num_replicas = dist.get_world_size()
if rank is None:
if not dist.is_available():
raise RuntimeError("Requires distributed package to be available")
rank = dist.get_rank()
self.dataset = dataset
self.num_replicas = num_replicas
self.rank = rank
self.shuffle = shuffle
self.num_repeats = num_repeats
self.epoch = 0
self.num_samples = int(math.ceil(len(self.dataset) * num_repeats / self.num_replicas))
self.total_size = self.num_samples * self.num_replicas
# Determine the number of samples to select per epoch for each rank.
# num_selected logic defaults to be the same as original RASampler impl, but this one can be tweaked
# via selected_ratio and selected_round args.
selected_ratio = selected_ratio or num_replicas # ratio to reduce selected samples by, num_replicas if 0
if selected_round:
self.num_selected_samples = int(math.floor(
len(self.dataset) // selected_round * selected_round / selected_ratio))
else:
self.num_selected_samples = int(math.ceil(len(self.dataset) / selected_ratio))
def __iter__(self):
# deterministically shuffle based on epoch
g = torch.Generator()
g.manual_seed(self.epoch)
if self.shuffle:
indices = torch.randperm(len(self.dataset), generator=g)
else:
indices = torch.arange(start=0, end=len(self.dataset))
# produce repeats e.g. [0, 0, 0, 1, 1, 1, 2, 2, 2....]
if isinstance(self.num_repeats, float) and not self.num_repeats.is_integer():
# resample for repeats w/ non-integer ratio
repeat_size = math.ceil(self.num_repeats * len(self.dataset))
indices = indices[torch.tensor([int(i // self.num_repeats) for i in range(repeat_size)])]
else:
indices = torch.repeat_interleave(indices, repeats=int(self.num_repeats), dim=0)
indices = indices.tolist() # leaving as tensor thrashes dataloader memory
# add extra samples to make it evenly divisible
padding_size = self.total_size - len(indices)
if padding_size > 0:
indices += indices[:padding_size]
assert len(indices) == self.total_size
# subsample per rank
indices = indices[self.rank:self.total_size:self.num_replicas]
assert len(indices) == self.num_samples
# return up to num selected samples
return iter(indices[:self.num_selected_samples])
def __len__(self):
return self.num_selected_samples
def set_epoch(self, epoch):
self.epoch = epoch
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