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WTF Is The NCCL Library and What Is It For?
Unlocking High-Speed GPU Communication for AI and HPC Workloads
AI models are growing. Fast. So fast, in fact, that training a single large language model can require hundreds — sometimes thousands — of GPUs working together in parallel.
But here’s the catch: it doesn’t matter how powerful your GPUs are if they can’t communicate efficiently with each other.
This is where NCCL, pronounced “Nickel,” comes in.
NCCL stands for NVIDIA Collective Communications Library — a low-level, high-performance communication library designed to enable fast, scalable, and efficient multi-GPU and multi-node communication.
If you’ve ever run distributed training on PyTorch or TensorFlow, chances are, NCCL was silently doing the heavy lifting behind the scenes.
It’s how your GPUs talk to each other at scale — without wasting time or bandwidth.
