[gmx-developers] Install both MPI and non-MPI GROMACS in a single location ?

[Gilles Gouaillardet]

Dear GROMACS developers,


On Fugaku (and many more supercomputers), GROMACS is installed via Spack.

End users generally use the MPI version for their jobs (e.g. cmake 
-DGMX_MPI=ON) but sometimes

prefer the serial version (e.g. -DGMX_MPI=OFF) for pre/post processing 
and/or single node thread-MPI.


 From a Spack usage point of view, it means two variants of GROMACS have 
to be installed

  - spack install gromacs +mpi

  - spack install gromacs -mpi

and it is up to the user to load the right module (and sometimes swap it 
in the middle of a script).


This is in my opinion not very user friendly and error prone.


I noted the serial and parallel variants generate different binaries 
(e.g. gmx_mpi vs gmx)

and common files (e.g. in the share directory), so I built a prototype 
recipe in which

both variants end up in the same spack module.


Before submitting it upstream, I would like to have your feedback as 
GROMACS developers:

Is it safe to install both serial and parallel variants of GROMACS in 
the same prefix?



Cheers,


Gilles