trunk/e632bee7b8c7e590b70bf70283dde89dc451c855: [c10d] Make nccl2 the default NCCL backend (#192281)
- PyTorch: 339 events in the last 90 days
- PyTorch: 336th Release in the last 90 days
- Previous: earlier the same day · ciflow/inductor/195410: Update
What happened
The standard nccl backend still selected legacy ProcessGroupNCCL unless users opted into nccl2 through an environment variable, even though the explicit nccl2 and nccl-legacy names make backend selection reversible. Invert the registration so an unset variable or TORCH_DIST_USE_NCCL2=1 selects nccl2, while TORCH_DIST_USE_NCCL2=0 and the explicit nccl-legacy name remain rollback paths. Defaulting also exposed three n…
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