The current documentation is given after installation
For Linux 64, Open MPI is built with CUDA awareness but this support is disabled by default.
To enable it, please set the environment variable OMPI_MCA_opal_cuda_support=true before
launching your MPI processes. Equivalently, you can set the MCA parameter in the command line:
mpiexec --mca opal_cuda_support 1 ...
In addition, the UCX support is also built but disabled by default.
To enable it, first install UCX (conda install -c conda-forge ucx). Then, set the environment
variables OMPI_MCA_pml="ucx" OMPI_MCA_osc="ucx" before launching your MPI processes.
Equivalently, you can set the MCA parameters in the command line:
mpiexec --mca pml ucx --mca osc ucx ...
Note that you might also need to set UCX_MEMTYPE_CACHE=n for CUDA awareness via UCX.
Please consult UCX's documentation for detail.