Fix torch_logs tutorial: gate CUDA check properly, allow CPU fallback

[ShriyashP]

Fixes #137285

Description

The torch_logs tutorial fails on CPU-only machines because torch.cuda.get_device_capability() is called unconditionally. This PR adds a torch.cuda.is_available() guard so the tutorial gracefully skips on CPU-only environments instead of crashing.

Changes

• Added torch.cuda.is_available() check before get_device_capability()
• Tutorial now falls back cleanly on CPU-only machines
• Updated inline comments for clarity

Testing

• Verified tutorial runs on CPU-only environment without errors
• No behavior change on CUDA-enabled machines

Checklist

• The issue that is being fixed is referred in the description (see above "Fixes #137285")
• Only one issue is addressed in this pull request
• Labels from the issue that this PR is fixing are added to this pull request
• No unnecessary issues are included into this pull request.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/tutorials/3821

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• Rolling out OSDC (ARC) runners on pull workflow for PyTorch trunk commits

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[meta-cla]

Hi @ShriyashP!

Thank you for your pull request and welcome to our community.

Action Required

In order to merge any pull request (code, docs, etc.), we require contributors to sign our Contributor License Agreement, and we don't seem to have one on file for you.

Process

In order for us to review and merge your suggested changes, please sign at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need to sign the corporate CLA.

Once the CLA is signed, our tooling will perform checks and validations. Afterwards, the pull request will be tagged with CLA signed. The tagging process may take up to 1 hour after signing. Please give it that time before contacting us about it.

If you have received this in error or have any questions, please contact us at cla@meta.com. Thanks!