report_step_statistics Subroutine

  subroutine report_step_statistics(istep, unit_in)
    use iso_fortran_env, only: output_unit
    use optionals, only: get_option_with_default
    implicit none
    integer, intent(in) :: istep
    integer, intent(in), optional :: unit_in
    integer :: unit
    unit = get_option_with_default(unit_in, output_unit)
    write(unit,'("Iteration : ",I0," Number of internal steps : ",I0," Number of failed steps : ",I0," Number of RHS calls : ",I0)') &
         istep, nsuccessful_steps, nfailed_steps, nrhs_calls
  end subroutine report_step_statistics