[Main] Support device-init grouped linear module too with when not using TE opfuser

[zhongbozhu]

• I, the PR author, have personally reviewed every line of this PR.

What does this PR do?

Proper single weight support, discrete weight is not affected. Adds many numerical unit tests running on GB200.

Unit testing:

Note: some tests can only run with TE updated (NVIDIA/TransformerEngine#3224), for CI image, it should just pass without causing errors.

pytest -s -v --confcutdir=tests/unit_tests/transformer/moe tests/unit_tests/transformer/moe/test_grouped_mlp.py

torchrun --nproc_per_node=4 --log-dir /tmp/mcore-single-weight-ut --tee 0:3 --redirects 3 -m pytest -s -v --confcutdir=tests/unit_tests/transformer/moe tests/unit_tests/transformer/moe/test_moe_single_grouped_weight_numerics.py

torchrun --nproc_per_node=4 --log-dir /tmp/mcore-grouped-dispatcher-ut --tee 0:3 --redirects 3 -m pytest -s -v --confcutdir=tests/unit_tests/transformer/moe tests/unit_tests/transformer/moe/test_grouped_tensor_dispatcher_numerics.py

⚠️ For major changes (either in lines of code or in its impact), please make sure to first share a design doc with the team. If you're unsure what's the best way to do so, contact @NVIDIA/mcore-oncall.

Issue tracking

For PRs from open-source community contributors:

• New features: a linked issue is required. Please open a feature request and reference it here before submitting the PR.
• Small updates (bug fixes, minor improvements): a linked issue is recommended and will accelerate the PR review process.

Linked issue:

Contribution process

Pre-checks

• 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

Feel free to message or comment @NVIDIA/mcore-oncall to help accelerate your merge into main. The less complex your PR is, the faster it will be approved and merged!

All PRs start as draft. If you open a non-draft PR, it will be automatically converted to draft.

Step 1: Mark PR as "Ready for Review"

1. When your PR is ready, click Ready for Review.
2. An oncall reviewer is auto-assigned and expert reviewers are notified based on your changes.
   • Some PRs may jump straight to step 2. This is determined by .github/CODEOWNERS.

⚠️ Only mark as ready once merge-conflicts are resolved and the CI is passing.
Final Review might get declined if these requirements are not fulfilled.

Step 2: Final Review

For PRs that change megatron/core, once all expert reviewers have approved, the Final Review label is applied automatically and final reviewers are assigned.

For PRs outside megatron/core, this step is skipped.

Step 3: Approved

Once all required reviewers have approved, the Approved label is applied automatically.

Merge

Any member of mcore-engineers will be able to merge your PR.

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.

[zhongbozhu]

/ok to test 1f647e6