mp_world_init Subroutine

   SUBROUTINE mp_world_init(mp_comm)
      !! initializes the system default communicator
      !! @note
      !! should only be called once

      INTEGER, INTENT(OUT)                     :: mp_comm
         !! [output] : handle of the default communicator
#if defined(__parallel)
      INTEGER                                  :: ierr
!$    INTEGER                                  :: provided_tsl
!$    LOGICAL                                  :: no_threading_support

#if defined(__NO_MPI_THREAD_SUPPORT_CHECK)
      ! Hack that does not request or check MPI thread support level.
      ! User asserts that the MPI library will work correctly with
      ! threads.
!
!$    no_threading_support = .TRUE.
#else
      ! Does the right thing when using OpenMP: requests that the MPI
      ! library supports funneled mode and verifies that the MPI library
      ! provides that support.
      !
      ! Developers: Only the master thread will ever make calls to the
      ! MPI library.
!
!$    no_threading_support = .FALSE.
#endif
!$    IF (no_threading_support) THEN
         CALL mpi_init(ierr)
         IF (ierr /= 0) CALL mp_stop(ierr, "mpi_init @ mp_world_init")
!$    ELSE
!$OMP MASTER
!$       CALL mpi_init_thread(MPI_THREAD_FUNNELED, provided_tsl, ierr)
!$       IF (ierr /= 0) CALL mp_stop(ierr, "mpi_init_thread @ mp_world_init")
!$       IF (provided_tsl .LT. MPI_THREAD_FUNNELED) THEN
!$          CALL mp_stop(0, "MPI library does not support the requested level of threading (MPI_THREAD_FUNNELED).")
!$       END IF
!$OMP END MASTER
!$    END IF
      CALL mpi_comm_set_errhandler(MPI_COMM_WORLD, MPI_ERRORS_RETURN, ierr)
      IF (ierr /= 0) CALL mp_stop(ierr, "mpi_comm_set_errhandler @ mp_world_init")
      mp_comm = MPI_COMM_WORLD
      debug_comm_count = 1
#else
      mp_comm = 0
#endif
      CALL add_mp_perf_env()
   END SUBROUTINE mp_world_init