"Jeff Squyres \(jsquyres\) via mpi-forum" <mpi-forum@lists.mpi-forum.org> writes:
> Let me ask a simple question: how will users to write portable MPI programs > in C with large count values? > > Answer: they will explicitly call MPI_Send_x(), and not rely on C11 _Generic. Few packages will accept a hard dependency on MPI-4 for at least 10 years. MS-MPI still doesn't fully support MPI-2.1, for example, and PETSc only recently began requiring MPI-2.0. Instead, each package that wishes to upgrade to MPI_Count args will write configure tests (autoconf, etc.) to detect availability of MPI_Send_x (as individual functions, not as MPI_VERSION == 4) and define macros/wrappers OurMPI_Send() that forwards to MPI_Send_x (when available) or MPI_Send (otherwise). When the implementation doesn't provide MPI_Send_x, they'll either have a smart wrapper that errors at run-time on truncation or (likely most apps) will silently fail with an FAQ that suggests using a compliant MPI-4 implementation. I'm not taking a position on C11 _Generic in the standard, but it would significantly reduce the configure complexity for apps to upgrade to MPI_Count without dropping support for previous standards. > Which then raises the question: what's the point of using C11 > _Generic? Its main functionality can lead to [potentially] silent > run-time errors, and/or require additional error checking in every > single code path by the implementation. That just seems like bad > design, IMNSHO. That's why the WG decided to bring this to the Forum > list (especially given the compressed timeframe for MPI-4). _______________________________________________ mpi-forum mailing list mpi-forum@lists.mpi-forum.org https://lists.mpi-forum.org/mailman/listinfo/mpi-forum
