This updates the nesting of if statements in `nn.Module._apply` such that if
`torch.__future__.set_swap_module_params_on_conversion(True)`, we always try to swap regardless of whether
- `torch._has_compatible_shallow_copy_type(param, fn(param)`
- `torch.__future__.set_overwrite_module_params_on_conversion` is set
This means that `meta_module.to_empty('device')` can now use the swap_tensors path cc @awgu
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120659
Approved by: https://github.com/albanD
Added a `torch.Tensor` method that defines how to transform `other`, a value in the state dictionary, to be loaded into `self`, a param/buffer in an `nn.Module` before swapping via `torch.utils.swap_tensors`
* `param.module_load(sd[key])`
This method can be overridden using `__torch_function__`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/117913
Approved by: https://github.com/albanD
Added `torch.__future__.{get/set}_swap_module_params_on_conversion` that defaults to `False` for now, but we probably want to modify to override this and default to `True` in `nn.Module._apply` if input is a tensor subclass.
From offline discussion, for now we are **not** allowing `swap_tensor` after the first module forward has been run*** if the autograd graph is still alive. The reason being that `torch.utils.swap_tensors(t1, t2)` requires the `use_count` of both `TensorImpl`s associated with `t1` and `t2` to be 1. The first forward pass will install `AccumulateGrad` nodes on each param, which [bump the refcount of the associated TensorImpl](6cf1fc66e3/torch/csrc/autograd/variable.cpp (L307)). **Future work might be to swap the refs that the `AccumulateGrad` nodes hold if it is necessary.**
***From this, it might seem like we don't need to handle gradients. However, I still handle the grads for the edge case that the grads are set via `p.grad = grad` OR the autograd graph is no longer alive because the output has been garbage collected.
If any `swap_tensors` fails on any of the parameters in the `nn.Module` we raise an error.
**`RNNBase` overrides `nn.Module._apply()` and installs weakrefs on some parameters. As a result, all modules that inherit from `RNNBase` (`RNN`, `GRU` and `LSTM`) cannot use the`swap_tensors` path as of now**
Pull Request resolved: https://github.com/pytorch/pytorch/pull/117167
Approved by: https://github.com/albanD
ghstack dependencies: #118028
Summary:
https://github.com/pytorch/pytorch/pull/17072 breaks `model.to(xla_device)`, because moving `model` to XLA device involves changing its parameters' TensorImpl type, and the current implementation of `nn.Module.to()` doesn't support changing module parameters' TensorImpl type:
```python
# 6dc445e1a8/torch/nn/modules/module.py (L192-L208)
def _apply(self, fn):
...
for param in self._parameters.values():
if param is not None:
# Tensors stored in modules are graph leaves, and we don't
# want to create copy nodes, so we have to unpack the data.
param.data = fn(param.data) # NOTE: this doesn't allow changing `param.data`'s TensorImpl type
if param._grad is not None:
param._grad.data = fn(param._grad.data) # NOTE: this doesn't allow changing `param._grad.data`'s TensorImpl type
...
```
yf225 TODO: fix the description here when we finish the implementation
To fix this problem, we introduce a new API `model.to_()` that always assign new tensors to the parameters (thus supporting changing the parameters to any TensorImpl type), and also bump the version counter of the original parameters correctly so that they are invalidated in any autograd graph they participate in.
We also add warning to the current `model.to()` API to inform users about the upcoming behavior change of `model.to()`: in future releases, it would create and return a new model instead of in-place updating the current model.
This unblocks adding XLA to our CI test suite, which also allows XLA to catch up with other changes in our codebase, notably the c10 dispatcher.
[xla ci]
cc. resistor ailzhang
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21613
Differential Revision: D15895387
Pulled By: yf225
fbshipit-source-id: b79f230fb06019122a37fdf0711bf2130a016fe6
