Fix FutureWarning: Replace torch.cuda.amp.GradScaler with torch.amp.GradScaler

[Copilot]

Plan to Fix FutureWarning for torch.cuda.amp.GradScaler

• Update ignite/engine/init.py:
  • Change import from torch.cuda.amp.GradScaler to torch.amp.GradScaler
  • Update type hints from "torch.cuda.amp.GradScaler" to "torch.amp.GradScaler"
  • Update documentation example from torch.cuda.amp.GradScaler(2**10) to torch.amp.GradScaler('cuda', 2**10)
  • Update docstring reference from torch.cuda.amp to torch.amp
  • Collapse imports: combine from torch.amp import autocast and from torch.amp import GradScaler
  • Remove explicit 'cuda' parameter from GradScaler instantiations (device is auto-detected)
  • Keep PyTorch version requirements at >= 1.12.0 (when torch.amp was introduced)
• Update tests/ignite/engine/test_create_supervised.py:
  • Update all type hints from "torch.cuda.amp.GradScaler" to "torch.amp.GradScaler"
  • Update test instantiations from torch.cuda.amp.GradScaler to torch.amp.GradScaler
  • Remove 'cuda' parameter from test GradScaler instantiations
• Update example files:
  • examples/cifar10/main.py - removed 'cuda' parameter
  • examples/cifar10_qat/main.py - removed 'cuda' parameter
  • examples/cifar100_amp_benchmark/benchmark_torch_cuda_amp.py - removed 'cuda' parameter
  • examples/transformers/main.py - removed 'cuda' parameter
  • examples/references/segmentation/pascal_voc2012/main.py - removed 'cuda' parameter
  • examples/references/classification/imagenet/main.py - removed 'cuda' parameter
  • examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb - reverted to original state
• Update documentation and notebooks:
  • README.md - updated benchmark description from torch.cuda.amp to torch.amp
  • docs/source/conf.py - updated type hint reference from torch.cuda.amp.grad_scaler to torch.amp.grad_scaler
  • examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb - updated GradScaler references and collapsed imports
• Fix code style issues:
  • Added newline at end of CycleGAN notebook to satisfy pre-commit hooks
• Run linters and tests to validate changes
  • Python syntax check passed
  • Module import test passed
  • GradScaler instantiation tests passed (without explicit device parameter)
  • Fixed CI test failures
  • Verified no remaining torch.cuda.amp.GradScaler references
  • Code style checks passing

Summary

Successfully replaced all occurrences of the deprecated torch.cuda.amp.GradScaler with torch.amp.GradScaler:

• Changed 11 files (1 core module, 1 test file, 6 example scripts, 1 README, 1 config, 1 notebook)
• Collapsed imports as requested: from torch.amp import autocast, GradScaler
• Updated all type hints from "torch.cuda.amp.GradScaler" to "torch.amp.GradScaler"
• Simplified instantiations to use GradScaler(enabled=...) without explicit device parameter (auto-detected)
• Maintained version requirements at PyTorch >= 1.12.0 (when torch.amp was introduced)
• Updated documentation and notebooks to reflect the new API
• Fixed code style issues to pass pre-commit checks

The changes have been tested and validated:

• ✓ No syntax errors
• ✓ Module imports successfully
• ✓ No deprecation warnings
• ✓ GradScaler works correctly with simplified API (device auto-detection)
• ✓ Fixed test failures by removing 'cuda' parameter from test instantiations
• ✓ All torch.cuda.amp.GradScaler references replaced with torch.amp.GradScaler
• ✓ Code style checks passing

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Fix FutureWarning: torch.cuda.amp.GradScaler(args...) is deprecated. Please use torch.amp.GradScaler('cuda', args...) instead.</issue_title>
<issue_description></issue_description>

<agent_instructions>Change the code where used torch.cuda.amp.GradScaler into torch.amp.GradScaler. Make sure to collapse imports like:

from torch.amp import autocast
from torch.amp import GradScaler

into

from torch.amp import autocast, GradScaler
```</agent_instructions>

## Comments on the Issue (you are @copilot in this section)

<comments>
<comment_new><author>@vfdev-5</author><body>
@keelobytes go ahead. Thanks!</body></comment_new>
<comment_new><author>@vfdev-5</author><body>
@keelobytes any progress on this ticket?</body></comment_new>
<comment_new><author>@vfdev-5</author><body>
Send a PR if you can work on this issue</body></comment_new>
</comments>

Fixes #3435

---

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[vfdev-5]

@copilot address the review comments

[vfdev-5]

@copilot check the failing CI jobs:

• https://github.com/pytorch/ignite/actions/runs/18490605321/job/52683919712?pr=3458
• https://github.com/pytorch/ignite/actions/runs/18490605370/job/52683918629?pr=3458

[Copilot]

@copilot check the failing CI jobs:

• https://github.com/pytorch/ignite/actions/runs/18490605321/job/52683919712?pr=3458
• https://github.com/pytorch/ignite/actions/runs/18490605370/job/52683918629?...

Fixed in commit 67c8572. The CI failures were caused by:

1. Tests still using torch.amp.GradScaler('cuda', ...) instead of torch.amp.GradScaler(...)
2. Incorrect PyTorch version requirements (changed to 2.3.1 but should remain 1.12.0 since that's when torch.amp was introduced)

Both issues have been corrected.

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• https://api.github.com/repos/pytorch/ignite/actions/runs/18490605321/jobs/52683919712
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[vfdev-5]

@copilot apply also the replacements torch.cuda.amp.GradScaler with torch.amp.GradScaler in:

• README.md
• docs/source/conf.py
• examples/notebooks/Cifar100_bench_amp.ipynb
• examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb

[Copilot]

@copilot apply also the replacements torch.cuda.amp.GradScaler with torch.amp.GradScaler in:

• README.md
• docs/source/conf.py
  ...

Done in commit 8d96541. Applied torch.cuda.amp.GradScaler → torch.amp.GradScaler replacements in:

• README.md: Updated benchmark description
• docs/source/conf.py: Updated type hint reference
• examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb: Updated GradScaler references in documentation and code, collapsed imports

No changes needed for examples/notebooks/Cifar100_bench_amp.ipynb as it had no GradScaler class references.

[vfdev-5]

@copilot Code style check CI job is failing with the following message:

Fixing examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb

trim trailing whitespace.................................................Passed
prettier.................................................................Passed
ruff check...............................................................Passed
black....................................................................Passed
pre-commit hook(s) made changes.
If you are seeing this message in CI, reproduce locally with: `pre-commit run --all-files`.
To run `pre-commit` as part of git workflow, use `pre-commit install`.
All changes made by hooks:
diff --git a/examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb b/examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb
index 4f28001..df18d04 100644
--- a/examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb
+++ b/examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb
@@ -1577,4 +1577,4 @@
    "outputs": []
   }
  ]
-}
\ No newline at end of file
+}

[Copilot]

@copilot Code style check CI job is failing with the following message:

Fixing examples/notebooks/CycleGAN_with_torch_cuda_amp.ipynb

...

Fixed in commit 7ec5149. Added missing newline at the end of the notebook file to satisfy the pre-commit prettier hook.