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Data interface
=========================
DataProto is the interface for data exchange.
The :class:`verl.DataProto` class contains two key members:
- batch: a :class:`tensordict.TensorDict` object for the actual data
- meta_info: a :class:`Dict` with additional meta information
TensorDict
~~~~~~~~~~~~
:attr:`DataProto.batch` is built on top of :class:`tensordict`, a project in the PyTorch ecosystem.
A TensorDict is a dict-like container for tensors. To instantiate a TensorDict, you must specify key-value pairs as well as the batch size.
.. code-block:: python
>>> import torch
>>> from tensordict import TensorDict
>>> tensordict = TensorDict({"zeros": torch.zeros(2, 3, 4), "ones": torch.ones(2, 3, 5)}, batch_size=[2,])
>>> tensordict["twos"] = 2 * torch.ones(2, 5, 6)
>>> zeros = tensordict["zeros"]
>>> tensordict
TensorDict(
fields={
ones: Tensor(shape=torch.Size([2, 3, 5]), device=cpu, dtype=torch.float32, is_shared=False),
twos: Tensor(shape=torch.Size([2, 5, 6]), device=cpu, dtype=torch.float32, is_shared=False),
zeros: Tensor(shape=torch.Size([2, 3, 4]), device=cpu, dtype=torch.float32, is_shared=False)},
batch_size=torch.Size([2]),
device=None,
is_shared=False)
One can also index a tensordict along its batch_size. The contents of the TensorDict can be manipulated collectively as well.
.. code-block:: python
>>> tensordict[..., :1]
TensorDict(
fields={
ones: Tensor(shape=torch.Size([1, 3, 5]), device=cpu, dtype=torch.float32, is_shared=False),
twos: Tensor(shape=torch.Size([1, 5, 6]), device=cpu, dtype=torch.float32, is_shared=False),
zeros: Tensor(shape=torch.Size([1, 3, 4]), device=cpu, dtype=torch.float32, is_shared=False)},
batch_size=torch.Size([1]),
device=None,
is_shared=False)
>>> tensordict = tensordict.to("cuda:0")
>>> tensordict = tensordict.reshape(6)
For more about :class:`tensordict.TensorDict` usage, see the official tensordict_ documentation.
.. _tensordict: https://pytorch.org/tensordict/overview.html
Core APIs
~~~~~~~~~~~~~~~~~
.. autoclass:: verl.DataProto
:members: to, select, union, make_iterator, concat