Troubleshooting

Hints

• If any issues need to be debugged, the following environment variables are very useful:

  • CUBLASMP_LOG_LEVEL environment variable to enable detailed logging of cuBLASMp operations

  • NCCL_DEBUG. For the broader set of NCCL diagnostics, refer to the NCCL environment variable documentation.

Known Issues

The issues below are relevant only when maintaining older cuBLASMp releases.

• cuBLASMp versions older than 0.8.0: During cublasMpGridCreate, NVSHMEM 3.4.5 and older may call exit() on unsupported platforms (e.g. arm64-sbsa + PCIe GPUs). For cuBLASMp 0.7.0, users can set CUBLASMP_DISABLE_NVSHMEM environment variable to 1 to work around this issue. cuBLASMp 0.8.0 and newer no longer use NVSHMEM.

• cuBLASMp versions older than 0.5.0: Some users may face hangs due to lazy initialization of NCCL in UCC. To disable the lazy NCCL initialization, please set UCC_TL_NCCL_LAZY_INIT environment variable to no.

• cuBLASMp versions older than 0.5.0: Some users may see errors with HPC-X v2.18 caused by a clash of UCC being initialized in OMPI and cuBLASMp. To disable UCC initialization in OMPI, please set OMPI_MCA_coll_ucc_enable environment variable to 0.