int MPI_Barrier(MPI_Comm communicator);

#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>

/**
 * @brief Illustrates how to use an MPI barrier.
 **/
int main(int argc, char* argv[])
{
    MPI_Init(&argc, &argv);

    // Get my rank
    int my_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    printf("[MPI process %d] I start waiting on the barrier.\n", my_rank);
    MPI_Barrier(MPI_COMM_WORLD);
    printf("[MPI process %d] I know all MPI processes have waited on the barrier.\n", my_rank);

    MPI_Finalize();

    return EXIT_SUCCESS;
}

SUBROUTINE MPI_Barrier(communicator, ierror)
    INTEGER :: communicator
    INTEGER :: ierror

!> @brief Illustrates how to use an MPI barrier.
PROGRAM main
    USE mpi

    IMPLICIT NONE

    INTEGER :: ierror
    INTEGER :: my_rank

    CALL MPI_Init(ierror)

    ! Get my rank
    CALL MPI_Comm_rank(MPI_COMM_WORLD, my_rank, ierror)

    WRITE(*,'(A,I0,A)') '[MPI process ', my_rank, '] I start waiting on the barrier.'
    CALL MPI_Barrier(MPI_COMM_WORLD, ierror)
    WRITE(*,'(A,I0,A)') '[MPI process ', my_rank, '] I know all MPI processes have waited on the barrier.'

    CALL MPI_Finalize(ierror)
END PROGRAM main

SUBROUTINE MPI_Barrier(communicator, ierror)
    TYPE(MPI_Comm), INTENT(IN) :: communicator
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

!> @brief Illustrates how to use an MPI barrier.
PROGRAM main
    USE mpi_f08

    IMPLICIT NONE

    INTEGER :: my_rank

    CALL MPI_Init()

    ! Get my rank
    CALL MPI_Comm_rank(MPI_COMM_WORLD, my_rank)

    WRITE(*,'(A,I0,A)') '[MPI process ', my_rank, '] I start waiting on the barrier.'
    CALL MPI_Barrier(MPI_COMM_WORLD)
    WRITE(*,'(A,I0,A)') '[MPI process ', my_rank, '] I know all MPI processes have waited on the barrier.'

    CALL MPI_Finalize()
END PROGRAM main