NCCL Extensions

NCCL Extensions is a repository of communication patterns for AI use cases,
built on top of NCCL device and host APIs. It speeds up tensor communication
for workloads like MoE token shuffle and reinforcement learning weight rollout.

This is an evolving space, and the content here is under constant development
and subject to change. We will continue exploring it and welcome your
contributions.

What's Inside

nccl_ep/ — Expert Parallelism

Optimized dispatch and combine primitives for Mixture-of-Experts (MoE) token
routing, built on NCCL's Device API (LSA and GIN operations).

nccl_m2n/ — Mesh-to-Mesh Rollout

Experimental library for resharding a tensor between two disjoint groups of
GPU processes (e.g. trainer and inference ranks) in a single, zero-copy call,
built on NCCL's window API.

python/ — Python bindings

Python package (nccl-extensions) providing Pythonic wrappers for nccl_ep.
See python/README.md for details.

Getting Started

This repo vendors NCCL as a git submodule. Clone with:

git clone --recursive <repo-url>

(or git submodule update --init --recursive after a normal clone). See each
subproject's README for build instructions.

Contributing

We welcome contributions! See CONTRIBUTING.md to get
started.

License

This project is licensed under the Apache License, Version 2.0 — see
LICENSE.txt for details.