如何解决错误：RuntimeError：收到 0 项 ancdata

Question

我有一个 torch.utils.data.DataLoader。我使用以下代码创建了它们。

transform_train = transforms.Compose([
    transforms.RandomCrop(32, padding=4),
    transforms.RandomHorizontalFlip(),
    transforms.ToTensor(),
    transforms.Normalize((0.4914, 0.4822, 0.4465), (0.2023, 0.1994, 0.2010)),
])

trainset = CIFAR100WithIdx(root='.',
                           train=True,
                           download=True,
                           transform=transform_train,
                           rand_fraction=args.rand_fraction)

train_loader = torch.utils.data.DataLoader(trainset,
                                           batch_size=args.batch_size,
                                           shuffle=True,
                                           num_workers=args.workers)

但是当我运行以下代码时出现错误。

train_loader_2 = []
for i, (inputs, target, index_dataset) in enumerate(train_loader):
    train_loader_2.append((inputs, target, index_dataset))

错误是

Traceback (most recent call last):
  File "main_superloss.py", line 460, in <module>
    main()
  File "main_superloss.py", line 456, in main
    main_worker(args)
  File "main_superloss.py", line 374, in main_worker
    train_loader, val_loader = get_train_and_val_loader(args)
  File "main_superloss.py", line 120, in get_train_and_val_loader
    for i, (inputs, target, index_dataset) in enumerate(train_loader):
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/site-packages/torch/utils/data/dataloader.py", line 804, in __next__
    idx, data = self._get_data()
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/site-packages/torch/utils/data/dataloader.py", line 771, in _get_data
    success, data = self._try_get_data()
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/site-packages/torch/utils/data/dataloader.py", line 724, in _try_get_data
    data = self.data_queue.get(timeout=timeout)
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/multiprocessing/queues.py", line 113, in get
    return _ForkingPickler.loads(res)
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/site-packages/torch/multiprocessing/reductions.py", line 284, in rebuild_storage_fd
    fd = df.detach()
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/multiprocessing/resource_sharer.py", line 58, in detach
    return reduction.recv_handle(conn)
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/multiprocessing/reduction.py", line 185, in recv_handle
    return recvfds(s, 1)[0]
  File "/home/C00423766/.conda/envs/dp/lib/python3.7/multiprocessing/reduction.py", line 161, in recvfds
    len(ancdata))
RuntimeError: received 0 items of ancdata

我想要获取列表中的数据的原因是因为我想对样本重新排序。而且不是以随机的方式，而是以特定的方式。我怎样才能做到这一点？

Answer 1

我的代码也面临类似的问题，并且基于一些讨论（检查#1、#2、#3）。我曾经ulimit -n 2048增加一个进程可以拥有的文件描述符的最大数量。您可以在此处阅读有关 ulimit 的更多信息。

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关于这个问题 - 讨论表明它必须对 pytorch\xe2\x80\x99s 分叉的多处理代码做一些事情。

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关于问题的第二部分，如何重新排序数据加载器 - 您可以参考这个答案

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