写一个fortran代码使用MPI并行的例子

好的，以下是一个简单的使用MPI并行的Fortran代码例子：

program main
  integer :: rank, size, ierr, i, sum = 0, my_sum = 0
  integer, parameter :: n = 1000
  integer, dimension(n) :: array
  call MPI_Init(ierr)
  call MPI_Comm_rank(MPI_COMM_WORLD, rank, ierr)
  call MPI_Comm_size(MPI_COMM_WORLD, size, ierr)
  ! Initialize array to rank
  do i = 1, n
    array(i) = rank
  end do
  ! Compute sum of elements in array for this process
  do i = 1 + (rank - 1) * (n / size), rank * (n / size)
    my_sum = my_sum + array(i)
  end do
  ! Combine all the sums
  call MPI_Reduce(my_sum, sum, 1, MPI_INTEGER, MPI_SUM, 0, MPI_COMM_WORLD, ierr)
  if (rank == 0) then
    write(*,*) 'The sum of all elements in the array is', sum
  end if
  call MPI_Finalize(ierr)
end program main