PyTorch 2.15 makes the rewritten NCCL backend the default
AIPyTorch 2.15 is released with a rewritten NCCL backend that is now the default for every nccl process group, with TORCH_DIST_USE_NCCL2=0 and nccl-legacy as rollback paths. The release also adds a flight recorder that dumps on hangs, FSDP2 precision and CUDA graph controls, and FP8 and decode speedups on Apple Silicon.
AIWhy it matters.
The release notes list concrete default changes, rollback paths, and deprecations, which matter for teams running distributed training or Apple Silicon inference.
Source details
PyTorch Blog · PyTorch Foundation · pytorch.orgPublished · added here
Original title: PyTorch 2.15 Release Blog