ParmParse::addfile needs Init

[ax3l]

Summary

ParmParse can be used before AMReX is initialized for most functionality, which is greatly helpful for us. One function that cannot be used before init is reading from a file, because it needs an MPI context to broadcast.

Add a clean error message instead of a segfault.

Additional background

cc @EZoni @RevathiJambunathan

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• include documentation in the code and/or rst files, if appropriate

[WeiqunZhang]

This does not work because amrex::Initialized() does not work during amrex::Initialize(). I think the way to do it is

#ifdef AMREX_USE_MPI
    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(ParallelDescriptor::Communicator() != MPI_COMM_NULL, "error message goes here");
#endif

[ax3l]

Agreed on the solution - but isn't the issue due to amrex::Error not working if AMReX is not initialized?

[WeiqunZhang]

That's right. So there are two issues. We cannot call amrex::Initialized() and ParallelDescriptor::Abort() here. So maybe we can do

#ifdef AMREX_USE_MPI
    if (ParallelDescriptor::Communicator() == MPI_COMM_NULL) {
        std::cerr << "......" << std::endl;
        std::abort();
    }
#endif

[ax3l]

Yes, but I would rather throw an exception.
This error is not fatal and one can recover in interactive contexts if we throw.