You might encounter problems when starting MPI applications via srun or mpirun. Both are responsible for launching multiple MPI tasks but might use different frameworks in the background to manage communications. Here are some general rules when to use what:

srun

  • Works for all Intel MPI libraries
  • Works for OpenMPI for foss/2019a to foss/2020b Toolchains
  • Does not work for OpenMPI >= foss/2021a on more than one node! → switch to mpirun in this case

mpirun

  • Works for all Intel MPI libraries
  • Works for OpenMPI for foss/2019a to foss/2020b Toolchains
  • Only works for OpenMPI  >= foss/2021a in combination with export OMPI_MCA_pml=ucx on more than one node
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