init_fields_implicit Subroutine

  subroutine init_fields_implicit
    use antenna, only: init_antenna
    use theta_grid, only: init_theta_grid
    use kt_grids, only: init_kt_grids, l_links, r_links
    use gs2_layouts, only: init_gs2_layouts
    use run_parameters, only: has_phi, has_apar, has_bpar
    use unit_tests, only: should_print
    use mp, only: mp_abort
    implicit none
    logical :: debug

    if (initialized) return
    initialized = .true.

    debug = should_print(3)

    !Check we have at least one field. If not abort.
    !Note, we do this here rather than as soon as we read input file
    !as other field types may support operation with no fields (e.g. 'local' does)
    if(.not. (has_phi .or. has_apar .or. has_bpar)) then
       call mp_abort("Field_option='implicit' requires at least one field is non-zero",.true.)
    endif

    if (debug) write(6,*) "init_fields_implicit: gs2_layouts"
    call init_gs2_layouts
    if (debug) write(6,*) "init_fields_implicit: theta_grid"
    call init_theta_grid
    if (debug) write(6,*) "init_fields_implicit: kt_grids"
    call init_kt_grids
    call setup_fields_implicit_class_arrays(l_links, r_links, M_class, N_class, i_class)
    if (debug) write(6,*) "init_fields_implicit: response_matrix"
    call init_response_matrix
    if (debug) write(6,*) "init_fields_implicit: antenna"
    call init_antenna
  end subroutine init_fields_implicit