NAMD Wiki: NamdOnUCX
The Charm++ ucx layer should provide higher performance than the verbs or mpi layers.
See https://charm.readthedocs.io/en/latest/charm++/manual.html#ucx for compilation details.
NAMD binaries built on the Charm++ ucx layer must be launched with an mpiexec binary that uses the launch mechanism (Simple PMI, Slurm PMI, Slurm PMI 2, or OpenMPI PMIx) for which they were built.
A bug in UCX that caused NAMD and other Charm++ applications to hang is corrected in UCX version 1.9.0-rc1 and later.