[Hardware] Replace torch.cuda.empty_cache with torch.accelerator.empty_cache

[jikunshang]

Purpose

vLLM is a framework support multi hardware backend. while there are some torch.cuda hard call. this is unfriendly to non-cuda compatible device. fortunately, there is a new set of torch.accelerator API which can dispatch based on platform.
I will try to create a series of PR to address this issue, start from empty_cache API.

Test Plan

CI.

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[chatgpt-codex-connector]

Codex usage limits have been reached for code reviews. Please check with the admins of this repo to increase the limits by adding credits.

[mergify]

Documentation preview: https://vllm--30681.org.readthedocs.build/en/30681/

[gemini-code-assist]

Code Review

This pull request replaces direct calls to torch.cuda.empty_cache() with the more hardware-agnostic torch.accelerator.empty_cache(). This is a good step towards making vLLM compatible with non-CUDA devices. The changes are applied consistently across the codebase, including in examples, utility functions, and core model execution logic. A new pre-commit hook is also added to prevent future usage of torch.cuda.empty_cache. My review focuses on the implementation of this new pre-commit hook, where I've found a couple of critical issues that would prevent it from working as intended. I've provided suggestions to fix them. The rest of the changes look good.

[gemini-code-assist]

The check current_file in ALLOWED_FILES performs an exact match, but ALLOWED_FILES contains directory prefixes. For example, a file tests/models/test_llama.py will not be matched against tests/. This will cause the pre-commit hook to incorrectly flag files that should be allowed. You should use startswith to check if the file path is under one of the allowed directories. Also, vllm/platforms/* seems to intend to match all files in the directory, so it should probably be vllm/platforms/.

Suggested change

	ALLOWED_FILES = {"tests/", "benchmarks/", "vllm/platforms/*"}
	def is_allowed_file(current_file: str) -> bool:
	return current_file in ALLOWED_FILES
	ALLOWED_FILES = {"tests/", "benchmarks/", "vllm/platforms/"}
	def is_allowed_file(current_file: str) -> bool:
	return any(current_file.startswith(p) for p in ALLOWED_FILES)

[gemini-code-assist]

re.match only checks for a match at the beginning of the string. This will fail to detect forbidden API calls that are not at the start of a line (after stripping whitespace), for example x = torch.cuda.empty_cache(). You should use re.search to find a match anywhere in the line.

Suggested change

	def is_forbidden_torch_cuda_api(line: str) -> bool:
	stripped = line.strip()
	return bool(_TORCH_CUDA_RE.match(stripped))
	def is_forbidden_torch_cuda_api(line: str) -> bool:
	return bool(_TORCH_CUDA_RE.search(line))

[hmellor]

We should pass file names, otherwise this will run on all files every commit

Suggested change

pass_filenames: false

[hmellor]

The hook doesn't need to work out which files it should run on, pre-commit already does that for us. Please look at tools/pre_commit/check_pickle_imports.py to see how this should be done