init_dt Subroutine

  subroutine init_dt (delt0, delt1, delt2, delt_max, istatus, not_set_value)
# ifdef NETCDF
    use mp, only: proc0, broadcast
    use file_utils, only: error_unit
    use optionals, only: get_option_with_default
# endif
    implicit none
    real, intent (in out) :: delt0, delt1, delt2, delt_max
    integer, intent (out) :: istatus
    real, intent(in), optional :: not_set_value
# ifdef NETCDF
    character (run_name_size) :: file_proc
    real :: not_set_value_to_use
    logical :: is_one_file_per_processor

    is_one_file_per_processor = read_many .or. (.not. has_netcdf_parallel)

    if (proc0) then
       file_proc = get_file_proc(is_one_file_per_processor)

       istatus = nf90_open (file_proc, NF90_NOWRITE, ncid)
       if (istatus /= NF90_NOERR) call netcdf_error (istatus,file=file_proc)

       not_set_value_to_use = get_option_with_default(not_set_value, -1.0)

       ! Note unlike the explicit source terms all three time steps should always
       ! be available in the restart file so we don't silence the error messages here.
       ! The only situation we are likely to come across where the delt1 and delt2
       ! values aren't available is where we are trying to read an old restart file.
       ! This will then lead to the error/warning being displayed but the code should
       ! carry on as intended and the missing steps will be set to a special value to
       ! indicate they have not been set yet.
       istatus = nf90_inq_varid (ncid, "delt0", delt0id)
       if (istatus /= NF90_NOERR) call netcdf_error (istatus, var='delt0')
       
       istatus = nf90_get_var (ncid, delt0id, delt0)

       if (istatus /= NF90_NOERR) then
          call netcdf_error (istatus, ncid, delt0id, message=' in init_dt')
          delt0 = not_set_value_to_use
       endif           

       istatus = nf90_inq_varid (ncid, "delt1", delt1id)
       if (istatus /= NF90_NOERR) call netcdf_error (istatus, var='delt1')
       
       istatus = nf90_get_var (ncid, delt1id, delt1)

       if (istatus /= NF90_NOERR) then
          call netcdf_error (istatus, ncid, delt1id, message=' in init_dt')
          delt1 = not_set_value_to_use
       endif           

       istatus = nf90_inq_varid (ncid, "delt2", delt2id)
       if (istatus /= NF90_NOERR) call netcdf_error (istatus, var='delt2')
       
       istatus = nf90_get_var (ncid, delt2id, delt2)

       if (istatus /= NF90_NOERR) then
          call netcdf_error (istatus, ncid, delt2id, message=' in init_dt')
          delt2 = not_set_value_to_use
       endif           

       istatus = nf90_inq_varid (ncid, "delt_max", delt_max_id)
       if (istatus /= NF90_NOERR) call netcdf_error (istatus, var='delt_max')

       istatus = nf90_get_var (ncid, delt_max_id, delt_max)

       if (istatus /= NF90_NOERR) then
          call netcdf_error (istatus, ncid, delt_max_id, message=' in init_dt')
          delt_max = not_set_value_to_use
       endif

       istatus = nf90_close (ncid)
    endif

    call broadcast (istatus)
    call broadcast (delt0)
    call broadcast (delt1)
    call broadcast (delt2)
    call broadcast (delt_max)

# endif
  end subroutine init_dt