Environment Variables

The following section lists the environment variables available to configure the cuDecomp library.

CUDECOMP_ENABLE_NCCL_UBR

(since v0.4.0, requires NCCL v2.19 or newer)

CUDECOMP_ENABLE_NCCL_UBR controls whether cuDecomp registers its communication buffers with the NCCL library using ncclCommRegister/ncclCommDeregister (i.e., user buffer registration). Registration can improve NCCL send/receive performance in some scenarios. See the User Buffer Registration section of the NCCL documentation for more details.

Default setting is off (0). Setting this variable to 1 will enable this feature.

CUDECOMP_ENABLE_CUMEM

(since v0.5.0, requires CUDA 12.3 driver/toolkit or newer)

CUDECOMP_ENABLE_CUMEM controls whether cuDecomp uses cuMem* APIs to allocate fabric-registered workspace buffers via cudecompMalloc. This option can improve the performance of some MPI distributions on multi-node NVLink (MNNVL) capable systems.

Default setting is off (0). Setting this variable to 1 will enable this feature.