run Subroutine

   subroutine run(im, lm, n_fields, output_filename)
      integer, intent(in) :: im
      integer, intent(in) :: lm
      integer, intent(in) :: n_fields
      character(*), intent(in) :: output_filename

      type (Netcdf4_Fileformatter) :: formatter
      type (FileMetadata) :: metadata
      real, allocatable :: field(:,:,:)

      integer :: jm
      integer :: j0, j1
      integer :: nj_local
      integer :: rank, npes, ierror
      integer :: j, n
      character(:), allocatable :: field_name
      character(3) :: field_idx_str

      call mpi_comm_size(MPI_COMM_WORLD, npes, ierror)
      _VERIFY(ierror)
      call mpi_comm_rank(MPI_COMM_WORLD, rank, ierror)
      _VERIFY(ierror)

      jm = im*6 ! pseudo cubed sphere
      call metadata%add_dimension('IM_WORLD', im)
      call metadata%add_dimension('JM_WORLD', jm)
      call metadata%add_dimension('LM', lm)

      do n = 1, n_fields
         write(field_idx_str,'(i3.3)') n
         field_name = 'field_' // field_idx_str
         call metadata%add_variable(field_name, Variable(pFIO_REAL32, dimensions='IM_WORLD,JM_WORLD,LM'))
      end do

      call formatter%create_par(output_filename, comm=MPI_COMM_WORLD)
      call formatter%write(metadata)

      j0 = 1 + rank*jm/npes
      j1 = (rank+1)*jm/npes
      nj_local = (j1 - j0) + 1
      allocate(field(im, nj_local, lm))

      do j = j0, j1
         field(:,j-j0+1,:) = j
      end do

      do n = 1, n_fields
         write(field_idx_str,'(i3.3)') n
         field_name = 'field_' // field_idx_str
         call formatter%put_var(field_name, field, start=[1,j0,1], count=[im,nj_local,lm])
      end do

      call formatter%close()
   end subroutine run