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import torch
from torch.utils.data import DistributedSampler as _DistributedSampler
class DistributedSampler(_DistributedSampler):
def __init__(self,
dataset,
num_replicas=None,
rank=None,
shuffle=True,
round_up=True):
super().__init__(dataset, num_replicas=num_replicas, rank=rank)
self.shuffle = shuffle
self.round_up = round_up
if self.round_up:
self.total_size = self.num_samples * self.num_replicas
else:
self.total_size = len(self.dataset)
def __iter__(self):
# deterministically shuffle based on epoch
if self.shuffle:
g = torch.Generator()
g.manual_seed(self.epoch)
indices = torch.randperm(len(self.dataset), generator=g).tolist()
else:
indices = torch.arange(len(self.dataset)).tolist()
# add extra samples to make it evenly divisible
if self.round_up:
indices = (
indices *
int(self.total_size / len(indices) + 1))[:self.total_size]
assert len(indices) == self.total_size
# subsample
indices = indices[self.rank:self.total_size:self.num_replicas]
if self.round_up:
assert len(indices) == self.num_samples
return iter(indices)
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