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Add documentation about NVLS all-reduce being a source of run-to-run non-determinism on Hopper NVSwitch nodes (H100, H20, H800) when the kernel driver / Fabric Manager is older than 550.144.03. Document that NCCL_NVLS_ENABLE=0 alone fixes single-request reproducibility with ~1% latency cost, vs ~76% for full batch invariance. Closes vllm-project#59352 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Signed-off-by: www6v <www6v@126.com>
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Summary
Add documentation about NVLS all-reduce being a source of run-to-run
non-determinism on Hopper NVSwitch nodes (H100, H20, H800) when the
kernel driver / Fabric Manager is older than 550.144.03.
Document that
NCCL_NVLS_ENABLE=0alone fixes single-requestreproducibility with ~1% latency cost, vs ~76% for full batch
invariance.
Closes #59352
Changes
docs/usage/reproducibility.md: Add NVSwitch (NVLS) non-determinism on Hopper section with a comparison tabledocs/features/batch_invariance.md: Add NVLS and fixed-batch reproducibility subsection under Implementation Details🤖 Generated with Claude Code