modern-cmake/specifics/MPI.md

MPI

To add MPI, like OpenMP, you'll be best off with CMake 3.9+.

find_package(MPI REQUIRED)
message(STATUS "Run: ${MPIEXEC} ${MPIEXEC_NUMPROC_FLAG} ${MPIEXEC_MAX_NUMPROCS} ${MPIEXEC_PREFLAGS} EXECUTABLE ${MPIEXEC_POSTFLAGS} ARGS")
target_link_libraries(MyTarget PUBLIC MPI::MPI_CXX)

However, you can imitate this on CMake 3.1+ with:

find_package(MPI REQUIRED)

# For supporting CMake < 3.9:
if(NOT TARGET MPI::MPI_CXX)
    add_library(MPI_LIB_TARGET INTERFACE)
    add_library(MPI::MPI_CXX ALIAS MPI_LIB_TARGET)

    target_compile_options(MPI_LIB_TARGET INTERFACE "${MPI_CXX_COMPILE_FLAGS}")
    target_include_directories(MPI_LIB_TARGET INTERFACE "${MPI_CXX_INCLUDE_PATH}")
    target_link_libraries(MPI_LIB_TARGET INTERFACE ${MPI_CXX_LINK_FLAGS} ${MPI_CXX_LIBRARIES})
endif()

message(STATUS "Run: ${MPIEXEC} ${MPIEXEC_NUMPROC_FLAG} ${MPIEXEC_MAX_NUMPROCS} ${MPIEXEC_PREFLAGS} EXECUTABLE ${MPIEXEC_POSTFLAGS} ARGS")
target_link_libraries(MyTarget PUBLIC MPI::MPI_CXX)

Or,

find_package(MPI REQUIRED)

# For supporting CMake < 3.9:

if(NOT TARGET MPI::MPI_CXX)
    add_library(MPI::MPI_CXX IMPORTED INTERFACE)

    set_property(TARGET MPI::MPI_CXX
                 PROPERTY INTERFACE_COMPILE_OPTIONS ${MPI_CXX_COMPILE_FLAGS})
    set_property(TARGET MPI::MPI_CXX
                 PROPERTY INTERFACE_INCLUDE_DIRECTORIES "${MPI_CXX_INCLUDE_PATH}")
    set_property(TARGET MPI::MPI_CXX
                 PROPERTY INTERFACE_LINK_LIBRARIES ${MPI_CXX_LINK_FLAGS} ${MPI_CXX_LIBRARIES})
endif()

message(STATUS "Run: ${MPIEXEC} ${MPIEXEC_NUMPROC_FLAG} ${MPIEXEC_MAX_NUMPROCS} ${MPIEXEC_PREFLAGS} EXECUTABLE ${MPIEXEC_POSTFLAGS} ARGS")
target_link_libraries(MyTarget PUBLIC MPI::MPI_CXX)