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For readers: We're doing this to support the pplx-kernel integration. We can use this structure for DeepEP as well.

Right now our fused MoE is implemented as something very very roughly like:

[Router] → [Quantize] → [Experts + topk_weight scaling + reduction]

This is a problem as the topk_weight scaling and reduction now need to happen during combine. We need to fit dispatch in there as well.

This PR defines a set of base classes used to make MoE kernels more modular. The goal is to be able to utilize different communication mechanisms with any fused MoE kernel without needing to have combinatoric implementations.

The fused moe kernels are broken down into the following components:

[Router] → [Quantize-Dispatch] → [Permute-Experts-Unpermute] → [Combine]

☝️ This is what @bnellnm and I agreed on. However:

The other option we originally considered was:

[Router] → [Quantize-Dispatch-Permute] → [Experts] → [Unpermute-Combine]

Right now I am thinking that permute/unpermute will (unfortunately) depend both on the implementation of both dispatch/combine and experts, so we should consider breaking that out.

One thing I forgot to put in our examples is -- Please call the destructor! ata.destroy()

One thing I forgot to put in our examples is -- Please call the destructor! ata.destroy()

Do all references to an AllToAll need to be destroyed? The current plan is to have a cache (that will be in a different PR) manage all the AllToAll instances and the PplxDispatchCombine would hold on to a reference of one of the cached objects.

Do all references to an AllToAll need to be destroyed?

No. Call destroy() only when you are shutting down the engine (or removing the model from GPU, etc...)

You are right to cache the object. It is supposed to be reused across layers and across runs.

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @bnellnm.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @bnellnm.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

I've verified that the following tests fail on main

pytest -sv tests/spec_decode/e2e/test_medusa_correctness.py::test_medusa_e2e_greedy_correctness_with_preemption[-1-1-4-128-test_llm_kwargs0-baseline_llm_kwargs0-per_test_common_llm_kwargs0-common_llm_kwargs0]
pytest -sv tests/spec_decode/e2e/test_eagle_correctness.py::test_eagle_e2e_greedy_correctness_with_preemption[1-4-128-test_llm_kwargs0-baseline_llm_kwargs0-per_test_common_llm_kwargs0-common_llm_kwargs0]

I'm not sure what is happening with the v1 test. I can't get it to fail locally on main or with this branch. But the model being run does not contain any MoE layers, so I think this failure is not related to this PR.