OpenMPI pml UCX is not working if ucx is not configured for multi threading (--enable-mt)
Description:
OpenMPI 5 is configured with (MPI_THREAD_MULTIPLE: yes) by default and in the archlinux package (openmpi-5.0.2-8). Current version of openucx (1.15.0-2) package doesn't enable multithreading (--enable-mt needs to be set in the local configure options for that). This makes the ucx pml unusable with openmpi (you get errors "pml_ucx.c:307 UCP worker does not support MPI_THREAD_MULTIPLE. PML UCX could not be selected") if you try MPI_init with thread multiple. Upstream reports are for example here: https://github.com/openucx/ucx/issues/5284
Could you add --enable-mt to the PKGBUILD under build/local_configure_option ? That solves the issue for me and I can use the UCX pml. Thanks.