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Extract compile-time and load-time constants from and MPI library. This is useful for libraries or applications that are not written in C, C++, or Fortran, and want to link against an MPI library as a binary dependency.

For the compile-time constants (e.g. MPI_VERSION), an executable generate_compile_time_mpi_constants is created that outputs their definitions.

For the load-time constants (e.g. MPI_COMM_WORLD), a shared library libload_time_mpi_constants.so is created that defines global variables holding the respective values.

Example output from generate_compile_time_mpi_constants:

  const MPI_VERSION_ = Cint(3)
  const MPI_SUBVERSION_ = Cint(1)

(This output is actually Julia code.)

Example definition in libload_time_mpi_constants.so:

const MPI_Comm MPICONSTANTS_COMM_NULL;
const MPI_Comm MPICONSTANTS_COMM_SELF;
const MPI_Comm MPICONSTANTS_COMM_WORLD;

This shared library can be loaded via dlopen, and the constants MPICONSTANTS_COMM_NULL etc. can be read to determine the respective values.

Thinking about new names

Should we rename things to sound more uniform? Maybe:

• Project: getmpiabi
• Executable: getmpiabi1
• Shared library: getmpiabi2

Using cmake to build this library

rm -rf build $HOME/src/c/MPIstuff/mpiconstants-openmpi
cmake -S . -B build -G Ninja -DMPIEXEC_EXECUTABLE=$(which mpiexec-openmpi-gcc11) -DCMAKE_C_COMPILER=mpicc-openmpi-gcc11 -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=$HOME/src/c/MPIstuff/mpiconstants-openmpi
cmake --build build
cmake --install build