HPC/UCPH
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MPI

MPI on multiple nodes

You need to allow passwordless ssh between nodes, for MPI to run on multiple nodes:

% ssh-keygen
#don't enter a password, just return,return,return
% cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

You can test it by ssh'ing from one frontend to another.

Please, read about "ssh keys" for more information.

mpi-selector

mpi-selector is a tool to control which MPI implementation and compiler to use for your MPI programs. After selection you must use mpicc to compile and mpirun to run your program.

Usage: call mpi-selector-menu and select one of the listed MPI implementations. Note, you can only change the per-user MPI implementation. When done with the selection, the changes will not be visible until you start a new shell (re-login).

Alternatively, you can also use the non-interactive tool mpi-selector. See 'man mpi-selector' for more information.

NOTE: mpi-selector will change the MPI implementation on a cluster-wide basis. This means, you cannot have multiple jobs using different MPI implementations. To do this, you need to setup the required environment variables in your job describtions.