compat-openmpi provides backwards-compatibility for older versions of openmpi (mpi-2 implementations). For EL6, the version is 1.4.x corresponding to the previous "super-stable" release of openmpi. It will also work for all applications compiled with or linked against openmpi v1.5.x.
To initialize the environment use the module command:
[pal]$ module avail # show available module; if module is undefined (bash) source /etc/profile.d/modules.sh [pal]$ module load compat-openmpi-x86_64 # initialize environment [pal]$ which mpiexec /usr/lib64/compat-openmpi/bin/mpiexec
The compat-packages only provide a runtime environment, no compiler!
Documentation:
openmpi has (like mpich, mvapich) an exhaustive number of options to tune compilation and runtime behavior. Please consult the openMPI documentations and FAQ: