cp: Megatron-FSDP Expert Parallel (DeepSeek-v3) Support into dev

[chtruong814]

What does this PR do ?

cp: Megatron-FSDP Expert Parallel (DeepSeek-v3) Support into dev

This was originally merged and then reverted due to failing internal tests. We need to address the test failure before merging again.

Contribution process

flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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Pre-checks

• I want this PR in a versioned release and have added the appropriate Milestone (e.g., Core 0.8)
• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
• I have run the autoformatter.sh on my PR

Code review

The following process is enforced via the CODEOWNERS file for changes into megatron/core. For changes outside of megatron/core, it is up to the PR author whether or not to tag the Final Reviewer team.

For MRs into `main` branch

(Step 1): Add PR label Expert Review

(Step 2): Collect the expert reviewers reviews

1. Attach the Expert Review label when your PR is ready for review.
2. GitHub auto-assigns expert reviewers based on your changes. They will get notified and pick up your PR soon.

⚠️ Only proceed to the next step once all reviewers have approved, merge-conflict are resolved and the CI is passing.
Final Review might get declined if these requirements are not fulfilled.

(Step 3): Final Review

1. Add Final Review label
2. GitHub auto-assigns final reviewers based on your changes. They will get notified and pick up your PR soon.

(Optional Step 4): Cherry-pick into release branch

If this PR also needs to be merged into core_r* release branches, after this PR has been merged, select Cherry-pick to open a new PR into the release branch.

For MRs into `dev` branch

The proposed review process for `dev` branch is under active discussion.

MRs are mergable after one approval by either eharper@nvidia.com or zijiey@nvidia.com.

Merging your PR

Any member of core-adlr and core-nemo will be able to merge your PR.

[BoxiangW]

LGTM

[Skylion007]

I ran this for a while and hit a weird issue where all the GPUs stop running computation, but NCCL_RAS indicated that it was not due to a NCCL collective issue. Error status was OK on all ranks and all ranks were responsive. May be related:

[Skylion007]

Suggested change

	logger.error(s)
	logger.error(''.join(traceback.format_stack()))
	logger.error(s, exc_info=True)

[BoxiangW]

Hi @Skylion007, thanks for the comments! Glad to have such an active user like you. This PR is actually a cherry-pick for dev branch. Its change is already merged into main branch here: 268fda0

[Skylion007]

Sigh, the graph I posted was from that commit then. :(

[BoxiangW]

@shjwudp @xuwchen Are you aware of this issue?