- en: DataLoader2 Tutorial
  id: totrans-0
  prefs:
  - PREF_H1
  type: TYPE_NORMAL
  zh: DataLoader2教程
- en: 原文：[https://pytorch.org/data/beta/dlv2_tutorial.html](https://pytorch.org/data/beta/dlv2_tutorial.html)
  id: totrans-1
  prefs:
  - PREF_BQ
  type: TYPE_NORMAL
  zh: 原文：[https://pytorch.org/data/beta/dlv2_tutorial.html](https://pytorch.org/data/beta/dlv2_tutorial.html)
- en: This is the tutorial for users to create a `DataPipe` graph and load data via
    `DataLoader2` with different backend systems (`ReadingService`). An usage example
    can be found in [this colab notebook](https://colab.research.google.com/drive/1eSvp-eUDYPj0Sd0X_Mv9s9VkE8RNDg1u).
  id: totrans-2
  prefs: []
  type: TYPE_NORMAL
  zh: 这是用户创建`DataPipe`图并通过不同后端系统(`ReadingService`)加载数据的教程。可以在[此colab笔记本](https://colab.research.google.com/drive/1eSvp-eUDYPj0Sd0X_Mv9s9VkE8RNDg1u)中找到一个使用示例。
- en: DataPipe[](#datapipe "Permalink to this heading")
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  prefs:
  - PREF_H2
  type: TYPE_NORMAL
  zh: DataPipe
- en: 'Please refer to [DataPipe Tutorial](dp_tutorial.html) for more details. Here
    are the most important caveats necessary: to make sure the data pipeline has different
    order per epoch and data shards are mutually exclusive and collectively exhaustive:'
  id: totrans-4
  prefs: []
  type: TYPE_NORMAL
  zh: 有关更多详细信息，请参阅[DataPipe教程](dp_tutorial.html)。以下是必要的最重要注意事项：确保数据管道每个时期具有不同的顺序，并且数据分片是互斥且完全穷尽的。
- en: Place `sharding_filter` or `sharding_round_robin_dispatch` as early as possible
    in the pipeline to avoid repeating expensive operations in worker/distributed
    processes.
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  prefs:
  - PREF_UL
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  zh: 尽早在管道中放置`sharding_filter`或`sharding_round_robin_dispatch`，以避免在工作/分布式进程中重复昂贵的操作。
- en: Add a `shuffle` DataPipe before sharding to achieve inter-shard shuffling. `ReadingService`
    will handle synchronization of those `shuffle` operations to ensure the order
    of data are the same before sharding so that all shards are mutually exclusive
    and collectively exhaustive.
  id: totrans-6
  prefs:
  - PREF_UL
  type: TYPE_NORMAL
  zh: 在分片之前添加一个`shuffle` DataPipe以实现分片间的洗牌。`ReadingService`将处理这些`shuffle`操作的同步，以确保在分片之前数据的顺序相同，以使所有分片互斥且完全穷尽。
- en: 'Here is an example of a `DataPipe` graph:'
  id: totrans-7
  prefs: []
  type: TYPE_NORMAL
  zh: 以下是一个`DataPipe`图的示例：
- en: '[PRE0]'
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  type: TYPE_PRE
  zh: '[PRE0]'
- en: Multiprocessing[](#multiprocessing "Permalink to this heading")
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  prefs:
  - PREF_H2
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  zh: 多进程
- en: '`MultiProcessingReadingService` handles multiprocessing sharding at the point
    of `sharding_filter` and synchronizes the seeds across worker processes.'
  id: totrans-10
  prefs: []
  type: TYPE_NORMAL
  zh: '`MultiProcessingReadingService` 在`sharding_filter`点处理多进程分片，并在工作进程之间同步种子。'
- en: '[PRE1]'
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  prefs: []
  type: TYPE_PRE
  zh: '[PRE1]'
- en: Distributed[](#distributed "Permalink to this heading")
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  prefs:
  - PREF_H2
  type: TYPE_NORMAL
  zh: 分布式
- en: '`DistributedReadingService` handles distributed sharding at the point of `sharding_filter`
    and synchronizes the seeds across distributed processes. And, in order to balance
    the data shards across distributed nodes, a `fullsync` `DataPipe` will be attached
    to the `DataPipe` graph to align the number of batches across distributed ranks.
    This would prevent hanging issue caused by uneven shards in distributed training.'
  id: totrans-13
  prefs: []
  type: TYPE_NORMAL
  zh: '`DistributedReadingService` 在`sharding_filter`点处理分布式分片，并在分布式进程之间同步种子。为了平衡分布式节点之间的数据分片，将在`DataPipe`图中附加一个`fullsync`
    `DataPipe`，以使分布式排名之间的批次数量保持一致。这将防止分布式训练中由不均匀分片引起的挂起问题。'
- en: '[PRE2]'
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  prefs: []
  type: TYPE_PRE
  zh: '[PRE2]'
- en: Multiprocessing + Distributed[](#multiprocessing-distributed "Permalink to this
    heading")
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  prefs:
  - PREF_H2
  type: TYPE_NORMAL
  zh: 多进程+分布式
- en: '`SequentialReadingService` can be used to combine both `ReadingServices` together
    to achieve multiprocessing and distributed training at the same time.'
  id: totrans-16
  prefs: []
  type: TYPE_NORMAL
  zh: '`SequentialReadingService`可用于将两个`ReadingServices`组合在一起，以同时实现多进程和分布式训练。'
- en: '[PRE3]'
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  prefs: []
  type: TYPE_PRE
  zh: '[PRE3]'