Hello, With UCX one has to define UCX environment variables to tune the runtime behaviour beside the commonly used mca parameters. This can lead - at least for me - to confusion as some of them seem to be "identical". Also, to my current experience only the UCX variables seem often to have an effect. Example: btl_*_eager_limit vs. UCX_RNDV_THRESH
Having now an external environment I am not totally sure, what the role of the mca parameters vs the UCX variables is (and the corresponding two tools ompi_info/ucx_info). For the moment at least I would welcome if the Open MPI documentation could include some more information and maybe best practices about this. Best Christoph Niethammer -- Christoph Niethammer High Performance Computing Center Stuttgart (HLRS) Nobelstrasse 19 70569 Stuttgart Tel: ++49(0)711-685-87203 email: nietham...@hlrs.de http://www.hlrs.de/people/niethammer
