The Art of Debugging Update: Diagnosing PyTorch NCCL Collective Hangs Efficiently

StasBekman · x · 2026-08-14

Stas Bekman has updated his open-source book The Art of Debugging with a new section on diagnosing buggy NCCL collective calls that cause PyTorch programs to hang.

The author noted that this diagnostic approach works even better than the popular py-spy tool, giving special thanks to the PyTorch team for their underlying debug tooling.

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