[WIP] Dflash2 implementation

[fynnsu]

Purpose

Implement support for training the new DFlash2 algorithm.

References:

• Blog: https://inco.ai/blog/dflash2/
• vLLM PR: [Spec Decode] DFlash2: local convolution + candidate selector vllm#52816
• DFlash repo: https://github.com/z-lab/dflash

Tests

Still a work in progress. Need to validate with training runs.

Checklist

I have filled in:

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan/results, such as providing test command and pasting the results.
• (Optional) The necessary documentation update.
• I (a human) have written or reviewed the code in this pr to the best of my ability.

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• DO NOT MERGE
• DRAFT

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[mergify]

Merge Protections

🔴 1 of 1 protections blocking · waiting on 👀 reviews

	Protection	Waiting on
🔴	Require approval from approved reviewers list	👀 reviews

🔴 Require approval from approved reviewers list

Waiting for any of

• approved-reviews-by = dsikka
• approved-reviews-by = fynnsu
• approved-reviews-by = orestis-z
• approved-reviews-by = rahul-tuli
• approved-reviews-by = shanjiaz

This rule is failing.

All pull requests must have at least one approving review from a member of the approved reviewers list before merging.

• any of:
  • approved-reviews-by = dsikka
  • approved-reviews-by = fynnsu
  • approved-reviews-by = orestis-z
  • approved-reviews-by = rahul-tuli
  • approved-reviews-by = shanjiaz

[mergify]

The quality checks have failed. Please run make style and make quality under
the root directory to address the lint failures. You will need to install the
dev optional install to get the required linting packages:
https://github.com/vllm-project/speculators/blob/main/CONTRIBUTING.md