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SLURM partitions

● available ● closed/not available

What remains unchanged

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• For users of SLURM’s srun job launcher:
  Open MPI 5.x has dropped support for the PMI-2 API, it solely depends on PMIx to bootstrap MPI processes. For this reason the environment setting was changed from SLURM_MPI_TYPE=pmi2 to SLURM_MPI_TYPE=pmix, so binaries linked against Open MPI can be started as usual “out of the box” using srun mybinary. For the case of a binary linked against Intel-MPI, this works too when a recent version (≥2021.11) of Intel-MPI has been used. If an older version of Intel-MPI has been used, and relinking/recompiling is not possible, one can follow the workaround for PMI-2 with srun as described in the Q&A section below. Switching from srun to mpirun instead should also be considered.

• Using more processes per node than available physical cores (PPN > 96; hyperthreads) with the OPX provider:
  The OPX provider currently does not support using hyperthreads/PPN > 96 on the clx partitions. Doing so may result in segmentation faults in libfabric during process startup. If a high number of PPN is really required, the default libfabric provider has to be changed to PSM2 by setting FI_PROVIDER=psm2. Note that the usage of hyperthreads may not advisable. We encourage users to test performance before using more threads than available physical cores.

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