ghstack-source-id: a0d1efd
Pull Request resolved: #124479

# Motivation
Refactor autocast usage scenario in `torch/amp/autocast_mode.py` and `torch/utils/checkpoint.py` to fix the bug - convention conflict between `torch.xxx.get_autocast_xxx_dtype` defined in `autocast_mode.py` and `torch.xxx.get_autocast_dtype` defined in `checkpoint.py`.

# Solution
Use device-agnostic APIs like `torch.get_autocast_dtype`, ..., instead.

Pull Request resolved: pytorch#124479
Approved by: https://github.com/jgong5, https://github.com/gujinghui, https://github.com/EikanWang, https://github.com/albanD
ghstack dependencies: pytorch#124359

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

cc mcarilli ptrblck leslie-fang-intel jgong5 ezyang msaroufim bdhirsh anijain2305 chauhang voznesenskym penguinwu EikanWang Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx chenyang78 kadeng

[ghstack-poisoned]

# Motivation
As discussed in [#124479](#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

Pull Request resolved: #125103
Approved by: https://github.com/albanD, https://github.com/jgong5, https://github.com/gujinghui

Summary:
# Motivation
As discussed in [#124479](pytorch/pytorch#124479), `torch.amp.autocast` can NOT be completely equivalent to `torch.cuda.amp.autocast` and `torch.cpu.amp.autocast` since `torch.amp.autocast` has NOT the default `dtype` for CPU (`torch.bfloat16` by default) and CUDA (`torch.float16` by default) respectively. We would like `torch.amp.autocast` to be more generic to help the developer/customer write the device-agnostic code. Because there are not enough reasons to add device-specific autocast `torch.xxx.amp.autocast` for each device backend.

# Solution
When `None` is passed to `dtype`, we should use `torch.get_autocast_dtype` to get the related dtype for each backend. Meanwhile, `torch.get_autocast_dtype` is necessary to be supported in JIT path for BC.

# Additional Context
With this PR, `torch.amp.autocast(device_type='cuda')` is equivalent to `torch.cuda.amp.autocast`.
Add two new UTs to cover this change in eager and jit path respectively.

X-link: pytorch/pytorch#125103
Approved by: https://github.com/albanD, https://github.com/jgong5, https://github.com/gujinghui

Reviewed By: izaitsevfb

Differential Revision: D57138276

fbshipit-source-id: 17f883924e43f68dd6836d99b06fe8a47cfccbf6

Refactor autocast usage scenario in `torch/amp/autocast_mode.py` and `torch/utils/checkpoint.py` to fix the bug - convention conflict between `torch.xxx.get_autocast_xxx_dtype` defined in `autocast_mode.py` and `torch.xxx.get_autocast_dtype` defined in `checkpoint.py`.

Use device-agnostic APIs like `torch.get_autocast_dtype`, ..., instead.

Pull Request resolved: #124479
Approved by: https://github.com/jgong5, https://github.com/gujinghui, https://github.com/EikanWang, https://github.com/albanD
ghstack dependencies: #124359

This reverts commit 495b0c9.

* Fix ref leak in `dtype.to_complex()`/`to_real()` (#125154)

By using `Py_NewRef`

Also, wrap `THPDtype_to_real`/`THPDtype_to_complex` calls with `HANDLE_TH_ERRORS`

Add regression test for the above issues, by calling to_complex for integral dtypes, that raises an exception and by preserving reference count to the same to_complex/to_real call to detect if leak is happeneing.

Replace
```cpp
auto dtype = (PyObject*)torch::getTHPDtype(current_dtype);
Py_INCREF(dtype);
return dtype;
```
with a more compact/streamlined equivalent
```cpp
return Py_NewRef(torch::getTHPDtype(current_dtype));
```

Fixes #124868

Pull Request resolved: #125154
Approved by: https://github.com/Skylion007, https://github.com/albanD

(cherry picked from commit 744f341)

* Revert "Fix ref leak in `dtype.to_complex()`/`to_real()` (#125154)"

This reverts commit a1b04d8.

* Fix ref leak in `dtype.to_complex()`/`to_real()` (#125154)

By using `Py_NewRef`

Also, wrap `THPDtype_to_real`/`THPDtype_to_complex` calls with `HANDLE_TH_ERRORS`

Add regression test for the above issues, by calling to_complex for integral dtypes, that raises an exception and by preserving reference count to the same to_complex/to_real call to detect if leak is happeneing.

Replace
```cpp
auto dtype = (PyObject*)torch::getTHPDtype(current_dtype);
Py_INCREF(dtype);
return dtype;
```
with a more compact/streamlined equivalent
```cpp
return Py_NewRef(torch::getTHPDtype(current_dtype));
```

Fixes #124868

Pull Request resolved: #125154
Approved by: https://github.com/Skylion007, https://github.com/albanD

(cherry picked from commit 744f341)

* Revert "Fix ref leak in `dtype.to_complex()`/`to_real()` (#125154)"

This reverts commit 5a28bad.

* Refactor autocast C++ APIs to be device-agnostic (#124359)

# Motivation
This PR aims to refactor autocast **C++** APIs to be device-agnostic and deprecate the device-specific autocast  **C++** APIs.
In C++ side,
- `is_enabled()` -> `is_enabled(device_type)`.
- `set_enabled(new_enabled)` -> `set_enabled(device_type, new_enabled)`.
- `get_autocast_dtype()` -> `get_autocast_dtype(device_type)`
- `set_autocast_dtype(dtype)` -> `set_autocast_dtype(device_type, dtype)`

These following C++ APIs are deprecated and should be removed in PyTorch 2.5
- `is_cpu_enabled`
- `set_cpu_enabled`
- `get_autocast_cpu_dtype`
- `set_autocast_cpu_dtype`
- `is_xpu_enabled`
- `set_xpu_enabled`
- `get_autocast_xpu_dtype`
- `set_autocast_xpu_dtype`
- `is_ipu_enabled`
- `set_ipu_enabled`
- `get_autocast_ipu_dtype`
- `set_autocast_ipu_dtype`
- `is_hpu_enabled`
- `set_hpu_enabled`
- `get_autocast_hpu_dtype`
- `set_autocast_hpu_dtype`
- `is_xla_enabled`
- `set_xla_enabled`
- `get_autocast_xla_dtype`
- `set_autocast_xla_dtype`
- `is_privateuseone_enabled`
- `set_privateuseone_enabled`
- `get_autocast_privateuseone_dtype`
- `set_autocast_privateuseone_dtype`

In Python side,
provide 4 generic autocast APIs:
- `torch.is_autocast_enabled(device_type)`
- `torch.set_autocast_enabled(device_type, new_enabled)`
- `torch.get_autocast_dtype(device_type)`
- `torch.set_autocast_dtype(device_type, dtype)`

# Additional Context
We will submit another PR to refactor autocast **Python** APIs based on this PR.

Pull Request resolved: #124359
Approved by: https://github.com/jgong5, https://github.com/albanD

* refactor autocast python APIs (#124479)

Refactor autocast usage scenario in `torch/amp/autocast_mode.py` and `torch/utils/checkpoint.py` to fix the bug - convention conflict between `torch.xxx.get_autocast_xxx_dtype` defined in `autocast_mode.py` and `torch.xxx.get_autocast_dtype` defined in `checkpoint.py`.

Use device-agnostic APIs like `torch.get_autocast_dtype`, ..., instead.

Pull Request resolved: #124479
Approved by: https://github.com/jgong5, https://github.com/gujinghui, https://github.com/EikanWang, https://github.com/albanD
ghstack dependencies: #124359

* Fix ref leak in `dtype.to_complex()`/`to_real()` (#125154)

By using `Py_NewRef`

Also, wrap `THPDtype_to_real`/`THPDtype_to_complex` calls with `HANDLE_TH_ERRORS`

Add regression test for the above issues, by calling to_complex for integral dtypes, that raises an exception and by preserving reference count to the same to_complex/to_real call to detect if leak is happeneing.

Replace
```cpp
auto dtype = (PyObject*)torch::getTHPDtype(current_dtype);
Py_INCREF(dtype);
return dtype;
```
with a more compact/streamlined equivalent
```cpp
return Py_NewRef(torch::getTHPDtype(current_dtype));
```

Fixes #124868

Pull Request resolved: #125154
Approved by: https://github.com/Skylion007, https://github.com/albanD

* Revert "refactor autocast python APIs (#124479)"

This reverts commit 495b0c9.

* Revert "Refactor autocast C++ APIs to be device-agnostic (#124359)"

This reverts commit 83106b7.

---------

Co-authored-by: Nikita Shulga <[email protected]>
Co-authored-by: Huy Do <[email protected]>
Co-authored-by: Yu, Guangye <[email protected]>