[Users] Error in exe/cactus_sim

[Roland Haas]

Hello Rishank,

> It's possible that you might have to uninstall mpich, but I'm not
> sure.  There *shouldn't* be a fundamental reason why you can't have
> both installed and just use one of them, but there might be technical
> reasons why it doesn't work.
It is possible to have both installed at the same time. However things
then become fragile. Ubuntu will declare one as the "default" using
either the "alternatives" system (which is why eg /usr/bin/mpi and
/usr/bin/mpicc point to files in /etc/alternatives/). This however does
not include things like eg hdf5 which come in flavor packages
hdf5-openmpi, hdf5-mpich, hdf5-serial each of which has libraries
libhdf5_{openmpi,mpich,serial}.so. Then there's always the possibility
something being wrong in the package setup.

Thus having multiple MPI stacks installed at the same time, while
possible, is outside of the realm of cases easily supported by our
automated setup and would likely require a hand-crafted option list
similar to the ones used on clusters. Eg setting

MPI_DIR = /usr/lib/x86_64-linux-gnu/openmpi
MPI_INC_DIRS = /usr/lib/x86_64-linux-gnu/openmpi/include
MPI_LIB_DIRS = /usr/lib/x86_64-linux-gnu/openmpi/lib
MPI_LIBS = mpi

*may* work (though see my note above about libraries that can use MPI).
Note that this still assumes that the mpirun found in $PATH is the one
that matches the used MPI stack, ie OpenMPI's so it may require changes
to the run script as well.

Thus the simplest solution is likely to make sure only one MPI stack
(OpenMPI or MPICH) is installed and uninstall the other one.

Yours,
Roland

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