To enable SHARP (Scalable Hierarchical Aggregation and Reduction Protocol) aggregation using the NCCL-SHARP plugin , the following two environment variables are required:

NCCL_COLLNET_ENABLE=1

Enables NCCL’s support for CollNet (Collective Network) operations, including SHARP.

NCCL_SHARP_AUTOINIT=1

Automatically initializes the SHARP plugin when available, activating SHARP-based collectives.

From the NVIDIA NCCL User Guide – SHARP Plugin Section :

"NCCL_COLLNET_ENABLE must be set to enable collective network acceleration features."

"NCCL_SHARP_AUTOINIT enables automatic SHARP plugin integration at NCCL runtime."

Incorrect Options:

B. NCCL_ALGO=CollNet – This variable controls the algorithm used for collectives but does not enable SHARP.

C. NCCLSPECTRUM_ENABLE – This is not a documented NCCL variable.