[gmx-developers] Whether or not to specify MPI compiler wrapper for MPI builds

[Eric Irrgang]

Hi Devs,

Is there a reason not to encourage CMake configuration with e..g. `-DCMAKE_CXX_COMPILER=mpicxx`?

The GROMACS install guide says "it is neither necessary nor recommended" but then gives this as the example syntax.
https://gitlab.com/gromacs/gromacs/-/blob/release-2021/docs/install-guide/index.rst#L226

It seems like providing the compiler wrapper to CMAKE_CXX_COMPILER would be the simplest and most robust way to get a self-consistent tool chain and to correctly hint the CMake FindMPI module.

I'd like to get feedback so that I can proceed with https://gitlab.com/gromacs/gromacs/-/issues/3672 and related tasks, but it would be good to resolve https://gitlab.com/gromacs/gromacs/-/issues/3671 so that we can have less confusing documentation for the 2021 release.

Thanks in advance for any insight.

Cheers!
Eric