pytorch/docs/source/distributed.checkpoint.rst
Chien-Chin Huang 19a6487ad4 [state_dict][6/N] Change API names to avoid conflict and simplify the API signatures (#111120)
`state_dict` is a very common variable name people use to represent a local
state_dict and `load_state_dict` conflicts with DCP's `load_state_dict`.

This PR changes `state_dict` to `get_state_dict`. `get_state_dict` is more close to what is this API does -- users use the API to get the current state_dict for saving or for loading (passed to DCP for loading in-place)..

This PR also changes `load_state_dict` to `set_state_dict`. `set_state_dict` is less ideal compared to `get_state_dict` but is symetric. We can still change the API name before it goes to beta.

This PR also simplies the API signatures. `model_only` is removed and `optim_only` only exists for `get_state_dict`.

Differential Revision: [D50213931](https://our.internmc.facebook.com/intern/diff/D50213931/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/111120
Approved by: https://github.com/wz337
ghstack dependencies: #111106, #111107, #111275, #111109, #111110
2023-10-17 00:15:31 +00:00

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.. role:: hidden
:class: hidden-section
Distributed Checkpoint - torch.distributed.checkpoint
=====================================================
Distributed Checkpoint (DCP) support loading and saving models from multiple ranks in parallel.
It handles load-time resharding which enables saving in one cluster topology and loading into another.
DCP is different than `torch.save` and `torch.load` in a few significant ways:
* It produces multiple files per checkpoint, with at least one per rank.
* It operates in place, meaning that the model should allocate its data first and DCP uses that storage instead.
The entrypoints to load and save a checkpoint are the following:
.. automodule:: torch.distributed.checkpoint
.. currentmodule:: torch.distributed.checkpoint
.. autofunction:: load_state_dict
.. autofunction:: save_state_dict
This `example <https://github.com/pytorch/pytorch/blob/main/torch/distributed/checkpoint/examples/fsdp_checkpoint_example.py>`_ shows how to use Pytorch Distributed Checkpoint to save a FSDP model.
The following types define the IO interface used during checkpoint:
.. autoclass:: torch.distributed.checkpoint.StorageReader
:members:
.. autoclass:: torch.distributed.checkpoint.StorageWriter
:members:
The following types define the planner interface used during checkpoint:
.. autoclass:: torch.distributed.checkpoint.LoadPlanner
:members:
.. autoclass:: torch.distributed.checkpoint.LoadPlan
:members:
.. autoclass:: torch.distributed.checkpoint.ReadItem
:members:
.. autoclass:: torch.distributed.checkpoint.SavePlanner
:members:
.. autoclass:: torch.distributed.checkpoint.SavePlan
:members:
.. autoclass:: torch.distributed.checkpoint.WriteItem
:members:
We provide a filesystem based storage layer:
.. autoclass:: torch.distributed.checkpoint.FileSystemReader
:members:
.. autoclass:: torch.distributed.checkpoint.FileSystemWriter
:members:
We provide default implementations of `LoadPlanner` and `SavePlanner` that
can handle all of torch.distributed constructs such as FSDP, DDP, ShardedTensor and DistributedTensor.
.. autoclass:: torch.distributed.checkpoint.DefaultSavePlanner
:members:
.. autoclass:: torch.distributed.checkpoint.DefaultLoadPlanner
:members:
We provide a set of APIs to help users do get and set state_dict easily. This is
an experimental feature and is subject to change.
.. autofunction:: torch.distributed.checkpoint.state_dict.get_state_dict
.. autofunction:: torch.distributed.checkpoint.state_dict.set_state_dict
.. autoclass:: torch.distributed.checkpoint.state_dict.StateDictOptions
:members: