[MISC] Fix triton import error

[MengqingCao]

Purpose

Fix triton import error in the scenario that triton is not installed. Actually we have make CI on this problem in #17716. However not sure why it is ineffective since this commit in https://github.com/vllm-project/vllm/pull/24440/commits. This pr is a quick fix on this issue

Test Plan

CI passed with pre-commit

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.

[gemini-code-assist]

Code Review

This pull request aims to fix a Triton import error when Triton is not installed by using the project's utility vllm.triton_utils. The change is correct in principle, but it introduces a runtime AttributeError because the TritonPlaceholder does not implement cdiv. I've added a critical comment with a suggestion to fix this within the changed file.

[gemini-code-assist]

While this change correctly uses the vllm.triton_utils placeholder for optional Triton import, it introduces a runtime error. The TritonPlaceholder used when Triton is not installed does not define the cdiv method. This file calls triton.cdiv in triton_mx_block_rearrange (lines 108, 109, 126, 127), which will raise an AttributeError if Triton is not present.

To fix this, you should replace all calls to triton.cdiv in this file with the local ceil_div function. This function is already defined at line 144 and used for the same purpose in the to_blocked function.

[DarkLight1337]

See #26654

[MengqingCao]

See #26654

Closing as duplicated with #26654