check_nonlinear_terms Subroutine

  subroutine check_nonlinear_terms(report_unit,delt_adj)
    use gs2_time, only: code_dt_min, code_dt_max
    use kt_grids, only: is_box
    use run_parameters, only: nstep, wstar_units
    use theta_grid, only: nperiod
    implicit none
    integer, intent(in) :: report_unit
    real, intent(in) :: delt_adj
    if (nonlin) then
       write (report_unit, *) 
       write (report_unit, fmt="('This is a nonlinear simulation.')")
       write (report_unit, *) 
       if (wstar_units) then
          write (report_unit, *) 
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('Nonlinear runs require wstar_units = .false. in the knobs namelist.')") 
          write (report_unit, fmt="('THIS IS AN ERROR.')") 
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *) 
       end if
       if ( .not. is_box) then
          write (report_unit, *) 
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('Nonlinear runs must be carried out in a box.')") 
          write (report_unit, fmt="('Set grid_option to box in the kt_grids_knobs namelist.')") 
          write (report_unit, fmt="('THIS IS AN ERROR.')") 
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *) 
       end if

       if (split_nonlinear) then
          write (report_unit, *)
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('The nonlinear term will be evolved separately from')")
          write (report_unit, fmt="('the linear terms in a crude IMEX style.')")
          write (report_unit, fmt="('This is an experimental feature.')")
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *)
       end if

       if (.not. include_apar) then
          write (report_unit, *)
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('The A|| potential contributions to the nonlinear term are disabled.')")
          write (report_unit, fmt="('This is probably an error.')")
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *)
       end if

       if (.not. include_bpar) then
          write (report_unit, *)
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('The B|| potential contributions to the nonlinear term are disabled.')")
          write (report_unit, fmt="('This is probably an error.')")
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *)
       end if

       if (.not. include_phi) then
          write (report_unit, *)
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('The electrostatic potential contributions to the nonlinear term are disabled.')")
          write (report_unit, fmt="('This is probably an error.')")
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *)
       end if

       if (nperiod > 1) then
          write (report_unit, *) 
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('Nonlinear runs usually have nperiod = 1.')") 
          write (report_unit, fmt="('THIS MAY BE AN ERROR.')") 
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *) 
       end if

       if (use_cfl_limit) then
          write (report_unit, *)
          write (report_unit, fmt="('The timestep will be adjusted to satisfy the CFL limit.')")
          write (report_unit, fmt="('The maximum delt < ',f10.4,' * min(Delta_perp/v_perp). (cfl)')") cfl
          write (report_unit, *)
       else
          write (report_unit, *)
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, fmt="('Nonlinear usually have use_cfl_limit = T')")
          write (report_unit, fmt="('################# WARNING #######################')")
          write (report_unit, *)
       end if

       if (use_order_based_error) then
          write (report_unit, *)
          write (report_unit, fmt="('The timestep will be adjusted to keep the estimated error below',e11.4)") error_target
          write (report_unit, fmt="('beginning on step',I0)") istep_error_start

          write (report_unit, *)
       else
          if (.not. use_cfl_limit) then
             write (report_unit, *)
             write (report_unit, fmt="('################# WARNING #######################')")
             write (report_unit, fmt="('Both CFL and error methods for controlling explicit timestep are disabled.')")
             write (report_unit, fmt="('THIS IS PROBABLY AN ERROR.')")
             write (report_unit, fmt="('################# WARNING #######################')")
             write (report_unit, *)
          end if
       end if

       write (report_unit, fmt="('The minimum delt ( code_dt_min ) = ',e11.4)") code_dt_min
       write (report_unit, fmt="('The maximum delt (code_dt_max) = ',e11.4)") code_dt_max
       write (report_unit, fmt="('When the time step needs to be changed, it is adjusted by a factor of ',f10.4)") delt_adj
       write (report_unit, fmt="('The number of time steps nstep = ',i7)") nstep
    endif
  end subroutine check_nonlinear_terms