mod_usr_methods.t

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!> Module with all the methods that users can customize in AMRVAC
!>
!> Each procedure pointer can be initialized in a user's mod_usr.t
module mod_usr_methods
 
  implicit none
  public
 
  !> Initialize the user's settings (after initializing amrvac)
  procedure(p_no_args), pointer       :: usr_set_parameters   => null()
  !> Initialize earch grid block data
  procedure(init_one_grid), pointer   :: usr_init_one_grid    => null()
 
  ! Boundary condition related
  procedure(special_bc), pointer      :: usr_special_bc       => null()
  procedure(special_prepare_bc), pointer      :: usr_prepare_boundary       => null()
  procedure(special_mg_bc), pointer   :: usr_special_mg_bc    => null()
 
  procedure(internal_bc), pointer     :: usr_internal_bc      => null()
 
  ! Output related
  procedure(p_no_args), pointer       :: usr_print_log        => null()
  procedure(p_no_args), pointer       :: usr_write_analysis   => null()
  procedure(transform_w), pointer     :: usr_transform_w      => null()
  procedure(aux_output), pointer      :: usr_aux_output       => null()
  procedure(add_aux_names), pointer   :: usr_add_aux_names    => null()
  procedure(sub_modify_io), pointer   :: usr_modify_output    => null()
  procedure(special_convert), pointer :: usr_special_convert  => null()
 
  ! Called at the beginning of every time step (after determining dt)
  procedure(process_grid), pointer    :: usr_process_grid     => null()
  procedure(process_global), pointer  :: usr_process_global   => null()
 
  ! Called every time step just after advance (with w^(n+1), it^n, global_time^n)
  procedure(process_adv_grid), pointer   :: usr_process_adv_grid   => null()
  procedure(process_adv_global), pointer :: usr_process_adv_global => null()
 
  ! Called after initial condition before the start of the simulation
  procedure(p_no_args), pointer       :: usr_improve_initial_condition => null()
 
  ! Called before the start of the simulation
  procedure(p_no_args), pointer       :: usr_before_main_loop => null()
 
  ! Source terms
  procedure(source), pointer          :: usr_source           => null()
  procedure(source), pointer          :: usr_source_after     => null()
  procedure(get_dt), pointer          :: usr_get_dt           => null()
  procedure(phys_gravity), pointer    :: usr_gravity          => null()
  procedure(sub_get_heating), pointer :: usr_get_heating      => null()
 
  ! Usr defined dust drag force
  procedure(phys_dust_get_dt), pointer :: usr_dust_get_dt     => null()
  procedure(phys_dust_get_3d_dragforce), pointer :: usr_get_3d_dragforce => null()
 
  ! Usr defined space varying viscosity
  procedure(set_viscosity), pointer   :: usr_set_viscosity    => null()
 
  ! Usr defined thermal pressure for hydro & energy=.False.
  procedure(hd_pthermal), pointer     :: usr_set_pthermal     => null()
 
  ! Refinement related procedures
  procedure(refine_grid), pointer     :: usr_refine_grid      => null()
  procedure(var_for_errest), pointer  :: usr_var_for_errest   => null()
  procedure(a_refine_threshold), pointer :: usr_refine_threshold => null()
  procedure(flag_grid), pointer       :: usr_flag_grid        => null()
 
  ! Set time-independent magnetic field for B0 splitting
  procedure(set_b0), pointer          :: usr_set_b0           => null()
  ! Set time-independent variables for equilibrium splitting, except for B0
  procedure(set_equi_vars), pointer   :: usr_set_equi_vars           => null()
  ! Set time-independent current density for B0 splitting
  procedure(set_j0), pointer          :: usr_set_j0           => null()
  procedure(special_resistivity), pointer :: usr_special_resistivity => null()
 
  ! Particle module related
  procedure(update_payload), pointer    :: usr_update_payload    => null()
  procedure(create_particles), pointer  :: usr_create_particles  => null()
  procedure(check_particle), pointer    :: usr_check_particle    => null()
  procedure(particle_fields), pointer   :: usr_particle_fields   => null()
  procedure(particle_analytic), pointer :: usr_particle_analytic => null()
  procedure(particle_position), pointer :: usr_particle_position => null()
 
  ! Radiation quantity related
  procedure(special_opacity), pointer   :: usr_special_opacity => null()
  procedure(special_fluxlimiter), pointer   :: usr_special_fluxlimiter => null()
  procedure(special_diffcoef), pointer   :: usr_special_diffcoef => null()
 
  ! Called after the mesh has been adjuste
  procedure(after_refine), pointer      :: usr_after_refine => null()
 
  ! initialize vector potential on cell edges for magnetic field
  procedure(init_vector_potential), pointer :: usr_init_vector_potential => null()
 
  ! allow user to change inductive electric field, especially for boundary driven applications
  procedure(set_electric_field), pointer :: usr_set_electric_field => null()
 
  ! allow user to specify variables at physical boundaries
  procedure(set_wlr), pointer :: usr_set_wlr => null()
 
  ! allow user to specify the expansion function for the surface of a cross sectional
  ! area of a 1D prominence, along with the analytical derivative of that function and its
  ! primitive shape evaluated in the boundaries \int_(x_i-dx_i/2)^(x_i+dx_i/2) A(s) ds
  procedure(set_surface), pointer  :: usr_set_surface          => null()
 
  ! for tracing field. allow user to specify variables and field
  procedure(set_field_w), pointer :: usr_set_field_w => null()
  procedure(set_field), pointer :: usr_set_field => null()
 
  ! allow user to specify R factor in ideal gas law with partial ionization
  procedure(rfactor), pointer :: usr_rfactor => null()
 
  ! allow user to specify adiabatic index and gamma dependent on space
  procedure(set_adiab), pointer :: usr_set_adiab => null()
  procedure(set_adiab), pointer :: usr_set_gamma => null()
 
  abstract interface
 
    subroutine p_no_args()
    end subroutine p_no_args
 
    !> Initialize one grid
    subroutine init_one_grid(ixI^L,ixO^L,w,x)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(inout) :: w(ixI^S,1:nw)
    end subroutine init_one_grid
 
     !> special boundary types, users must assign conservative
     !> variables in boundaries
     subroutine special_bc(qdt,qt,ixI^L,ixO^L,iB,w,x)
       use mod_global_parameters
       !> Shape of input arrays
       integer, intent(in)             :: ixI^L
       !> Region where boundary values have to be set
       integer, intent(in)             :: ixO^L
       !> Integer indicating direction of boundary
       integer, intent(in)             :: iB
       double precision, intent(in)    :: qdt,qt, x(ixI^S,1:ndim)
       double precision, intent(inout) :: w(ixI^S,1:nw)
     end subroutine special_bc
 
     subroutine special_prepare_bc(qt,qdt)
       use mod_global_parameters
       double precision, intent(in) :: qt, qdt
     end subroutine special_prepare_bc
 
     !> Special boundary type for radiation hydrodynamics module, only used to
     !> set the boundary conditions for the radiation energy.
     subroutine special_mg_bc(iB)
       use mod_global_parameters
       integer, intent(in)             :: iB
     end subroutine special_mg_bc
 
    !> internal boundary, user defined
    !> This subroutine can be used to artificially overwrite ALL conservative
    !> variables in a user-selected region of the mesh, and thereby act as
    !> an internal boundary region. It is called just before external (ghost cell)
    !> boundary regions will be set by the BC selection. Here, you could e.g.
    !> want to introduce an extra variable (nwextra, to be distinguished from nwaux)
    !> which can be used to identify the internal boundary region location.
    !> Its effect should always be local as it acts on the mesh.
    subroutine internal_bc(level,qt,qdt,ixI^L,ixO^L,w,x)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L,ixO^L,level
      double precision, intent(in)    :: qt, qdt
      double precision, intent(inout) :: w(ixI^S,1:nw)
      double precision, intent(in)    :: x(ixI^S,1:ndim)
    end subroutine internal_bc
 
    !> this subroutine is ONLY to be used for computing auxiliary variables
    !> which happen to be non-local (like div v), and are in no way used for
    !> flux computations. As auxiliaries, they are also not advanced
    subroutine process_grid(igrid,level,ixI^L,ixO^L,qt,w,x)
      use mod_global_parameters
      integer, intent(in)             :: igrid,level,ixI^L,ixO^L
      double precision, intent(in)    :: qt,x(ixI^S,1:ndim)
      double precision, intent(inout) :: w(ixI^S,1:nw)
    end subroutine process_grid
 
    !> If defined, this routine is called before writing output, and it can
    !> set/modify the variables in the w array.
    subroutine sub_modify_io(ixI^L,ixO^L,qt,w,x)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L,ixO^L
      double precision, intent(in)    :: qt,x(ixI^S,1:ndim)
      double precision, intent(inout) :: w(ixI^S,1:nw)
    end subroutine sub_modify_io
 
    !> This subroutine is called at the beginning of each time step
    !> by each processor. No communication is specified, so the user
    !> has to implement MPI routines if information has to be shared
    subroutine process_global(iit,qt)
      use mod_global_parameters
      integer, intent(in)          :: iit
      double precision, intent(in) :: qt
    end subroutine process_global
 
    !> for processing after the advance (PIC-MHD, e.g.)
    subroutine process_adv_grid(igrid,level,ixI^L,ixO^L,qt,w,x)
      use mod_global_parameters
      integer, intent(in)             :: igrid,level,ixI^L,ixO^L
      double precision, intent(in)    :: qt,x(ixI^S,1:ndim)
      double precision, intent(inout) :: w(ixI^S,1:nw)
    end subroutine process_adv_grid
 
    !> for processing after the advance (PIC-MHD, e.g.)
    subroutine process_adv_global(iit,qt)
      use mod_global_parameters
      integer, intent(in)          :: iit
      double precision, intent(in) :: qt
    end subroutine process_adv_global
 
    !> this subroutine can be used in convert, to add auxiliary variables to the
    !> converted output file, for further analysis using tecplot, paraview, ....
    !> these auxiliary values need to be stored in the nw+1:nw+nwauxio slots
    !
    !> the array normconv can be filled in the (nw+1:nw+nwauxio) range with
    !> corresponding normalization values (default value 1)
    subroutine aux_output(ixI^L,ixO^L,w,x,normconv)
      use mod_global_parameters
      integer, intent(in)          :: ixI^L,ixO^L
      double precision, intent(in) :: x(ixI^S,1:ndim)
      double precision             :: w(ixI^S,nw+nwauxio)
      double precision             :: normconv(0:nw+nwauxio)
    end subroutine aux_output
 
    !> Add names for the auxiliary variables
    subroutine add_aux_names(varnames)
      use mod_global_parameters
      character(len=*) :: varnames
    end subroutine add_aux_names
 
    !> Calculate w(iw)=w(iw)+qdt*SOURCE[wCT,qtC,x] within ixO for all indices
    !> iw=iwmin...iwmax.  wCT is at time qCT
    subroutine source(qdt,ixI^L,ixO^L,iw^LIM,qtC,wCT,qt,w,x)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L, iw^LIM
      double precision, intent(in)    :: qdt, qtC, qt
      double precision, intent(in)    :: wCT(ixI^S,1:nw), x(ixI^S,1:ndim)
      double precision, intent(inout) :: w(ixI^S,1:nw)
    end subroutine source
 
    !> Limit "dt" further if necessary, e.g. due to the special source terms.
    !> The getdt_courant (CFL condition) and the getdt subroutine in the AMRVACPHYS
    !> module have already been called.
    subroutine get_dt(w,ixI^L,ixO^L,dtnew,dx^D,x)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: dx^D, x(ixI^S,1:ndim)
      double precision, intent(in)    :: w(ixI^S,1:nw)
      double precision, intent(inout) :: dtnew
    end subroutine get_dt
 
    !> Calculate gravitational acceleration in each dimension
    subroutine phys_gravity(ixI^L,ixO^L,wCT,x,gravity_field)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(in)    :: wCT(ixI^S,1:nw)
      double precision, intent(out)   :: gravity_field(ixI^S,ndim)
    end subroutine phys_gravity
 
    !> Calculate the 3d drag force of gas onto dust
    subroutine phys_dust_get_3d_dragforce(ixI^L, ixO^L, w, x, fdrag, ptherm, vgas,dust_n_species)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L, dust_n_species
      double precision, intent(in)    :: x(ixI^S, 1:ndim)
      double precision, intent(in)    :: w(ixI^S, 1:nw)
      double precision, intent(out)   :: &
           fdrag(ixI^S, 1:ndir, 1:dust_n_species)
      double precision, intent(in)    :: ptherm(ixI^S), vgas(ixI^S, ndir)
    end subroutine phys_dust_get_3d_dragforce
 
    !> Calculate the time step associated with the usr drag force
    subroutine phys_dust_get_dt(w, ixI^L, ixO^L, dtdust, dx^D, x, dust_n_species)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L, dust_n_species
      double precision, intent(in)    :: dx^D, x(ixI^S,1:ndim)
      double precision, intent(in)    :: w(ixI^S,1:nw)
      double precision, intent(inout) :: dtdust(1:dust_n_species)
    end subroutine phys_dust_get_dt
 
    !>Calculation anormal viscosity depending on space
    subroutine set_viscosity(ixI^L,ixO^L,x,wp,mu)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(in)    :: wp(ixI^S,1:nw) ! primitive w
      double precision, intent(out)   :: mu(ixI^S)
    end subroutine set_viscosity
 
    !>Calculation anormal pressure for hd & energy=.False.
    subroutine hd_pthermal(w,x,ixI^L,ixO^L,pth)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(in)    :: w(ixI^S,1:nw)
      double precision, intent(out)   :: pth(ixI^S)
    end subroutine hd_pthermal
 
    !>Calculation R factor for ideal gas law with partial ionization
    subroutine rfactor(w,x,ixI^L,ixO^L,pth)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(in)    :: w(ixI^S,1:nw)
      double precision, intent(out)   :: pth(ixI^S)
    end subroutine rfactor
 
    !>set adiabatic index
    subroutine set_adiab(w,x,ixI^L,ixO^L,adiab)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(in)    :: w(ixI^S,1:nw)
      double precision, intent(out)   :: adiab(ixI^S)
    end subroutine set_adiab
 
    !> Set the "eta" array for resistive MHD based on w or the
    !> "current" variable which has components between idirmin and 3.
    subroutine special_resistivity(w,ixI^L,ixO^L,idirmin,x,current,eta)
      use mod_global_parameters
      integer, intent(in)          :: ixI^L, ixO^L, idirmin
      double precision, intent(in) :: w(ixI^S,nw), x(ixI^S,1:ndim)
      double precision, intent(in) :: current(ixI^S,7-2*ndir:3)
      double precision, intent(out) :: eta(ixI^S)
    end subroutine special_resistivity
 
 
    !> Set user defined opacity for use in diffusion coeff, heating and cooling, and radiation force
    subroutine special_opacity(ixI^L,ixO^L,w,x,kappa)
      use mod_global_parameters
      integer, intent(in)          :: ixI^L, ixO^L
      double precision, intent(in) :: w(ixI^S,1:nw), x(ixI^S,1:ndim)
      double precision, intent(out):: kappa(ixI^S)
    end subroutine special_opacity
 
    !> Set user defined FLD flux limiter, lambda
    subroutine special_fluxlimiter(ixI^L,ixO^L,w,x,fld_lambda,fld_R)
      use mod_global_parameters
      integer, intent(in)          :: ixI^L, ixO^L
      double precision, intent(in) :: w(ixI^S,1:nw), x(ixI^S,1:ndim)
      double precision, intent(out):: fld_lambda(ixI^S),fld_R(ixI^S)
    end subroutine special_fluxlimiter
 
    !> Set user defined FLD diffusion coefficient
    subroutine special_diffcoef(w, wprim, x, ixI^L, ixO^L)
      use mod_global_parameters
      integer, intent(in)          :: ixI^L, ixO^L
      double precision, intent(inout) :: w(ixI^S, 1:nw)
      double precision, intent(in) :: wprim(ixI^S, 1:nw)
      double precision, intent(in) :: x(ixI^S, 1:ndim)
    end subroutine special_diffcoef
 
    !> Enforce additional refinement or coarsening
    !> One can use the coordinate info in x and/or time qt=t_n and w(t_n) values w.
    !> you must set consistent values for integers refine/coarsen:
    !> refine = -1 enforce to not refine
    !> refine =  0 doesn't enforce anything
    !> refine =  1 enforce refinement
    !> coarsen = -1 enforce to not coarsen
    !> coarsen =  0 doesn't enforce anything
    !> coarsen =  1 enforce coarsen
    !> e.g. refine for negative first coordinate x < 0 as
    !> if (any(x(ix^S,1) < zero)) refine=1
    subroutine refine_grid(igrid,level,ixI^L,ixO^L,qt,w,x,refine,coarsen)
      use mod_global_parameters
      integer, intent(in)          :: igrid, level, ixI^L, ixO^L
      double precision, intent(in) :: qt, w(ixI^S,1:nw), x(ixI^S,1:ndim)
      integer, intent(inout)       :: refine, coarsen
    end subroutine refine_grid
 
    !> this is the place to compute a local auxiliary variable to be used
    !> as refinement criterion for the Lohner error estimator only
    !>  -->it is then requiring and iflag>nw
    !> note that ixO=ixI=ixG, hence the term local (gradients need special attention!)
    subroutine var_for_errest(ixI^L,ixO^L,iflag,w,x,var)
      use mod_global_parameters
      integer, intent(in)           :: ixI^L,ixO^L,iflag
      double precision, intent(in)  :: w(ixI^S,1:nw), x(ixI^S,1:ndim)
      double precision, intent(out) :: var(ixI^S)
    end subroutine var_for_errest
 
    !> Here one can add a steady (time-independent) potential background field
    subroutine set_b0(ixI^L,ixO^L,x,wB0)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L,ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(inout) :: wB0(ixI^S,1:ndir)
    end subroutine set_b0
 
    !> Here one can add a time-independent background current density
    subroutine set_j0(ixI^L,ixO^L,x,wJ0)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L,ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(inout) :: wJ0(ixI^S,7-2*ndir:ndir)
    end subroutine set_j0
 
    !> Here one can add a steady (time-independent) equi vars
    subroutine set_equi_vars(ixI^L,ixO^L,x,w0)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L,ixO^L
      double precision, intent(in)    :: x(ixI^S,1:ndim)
      double precision, intent(inout) :: w0(ixI^S,1:number_equi_vars)
    end subroutine set_equi_vars
 
    !> adjust w when restart from dat file with different w variables
    subroutine transform_w(ixI^L,ixO^L,nw_in,w_in,x,w_out)
      use mod_global_parameters
      integer, intent(in)           :: ixI^L, ixO^L, nw_in
      double precision, intent(in)  :: w_in(ixI^S,1:nw_in)
      double precision, intent(in)  :: x(ixI^S, 1:ndim)
      double precision, intent(out) :: w_out(ixI^S,1:nw)
    end subroutine transform_w
 
    !> use different threshold in special regions for AMR to
    !> reduce/increase resolution there where nothing/something interesting happens.
    subroutine a_refine_threshold(wlocal,xlocal,threshold,qt,level)
      use mod_global_parameters
      double precision, intent(in)    :: wlocal(1:nw),xlocal(1:ndim),qt
      double precision, intent(inout) :: threshold
      integer, intent(in) :: level
    end subroutine a_refine_threshold
 
    !> Allow user to use their own data-postprocessing procedures
    subroutine special_convert(qunitconvert)
      use mod_global_parameters
      integer, intent(in) :: qunitconvert
      character(len=20)   :: userconvert_type
    end subroutine special_convert
 
    !> flag=-1 : Treat all cells active, omit deactivation (onentry, default)
    !> flag=0  : Treat as normal domain
    !> flag=1  : Treat as passive, but reduce by safety belt
    !> flag=2  : Always treat as passive
    subroutine flag_grid(qt,ixI^L,ixO^L,w,x,flag)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L
      integer, intent(inout)          :: flag
      double precision, intent(in)    :: qt
      double precision, intent(inout) :: w(ixI^S,1:nw)
      double precision, intent(in)    :: x(ixI^S,1:ndim)
    end subroutine flag_grid
 
    !> Update payload of particles
    subroutine update_payload(igrid,x,u,q,m,mypayload,mynpayload,particle_time)
      use mod_global_parameters
      integer, intent(in)           :: igrid,mynpayload
      double precision, intent(in)  :: x(1:ndir),u(1:ndir),q,m,particle_time
      double precision, intent(out) :: mypayload(mynpayload)
    end subroutine update_payload
 
    !> Create particles
    subroutine create_particles(n_particles, x, v, q, m, follow)
      integer, intent(in)           :: n_particles
      double precision, intent(out) :: x(3, n_particles)
      double precision, intent(out) :: v(3, n_particles)
      double precision, intent(out) :: q(n_particles)
      double precision, intent(out) :: m(n_particles)
      logical, intent(out)          :: follow(n_particles)
    end subroutine create_particles
 
    !> Check arbitrary particle conditions or modifications
    subroutine check_particle(igrid,x,v,q,m,follow,check)
      use mod_global_parameters
      integer, intent(in)           :: igrid
      double precision, intent(inout) :: x(1:ndir)
      double precision, intent(inout) :: v(1:ndir),q,m
      logical, intent(inout) :: follow
      logical, intent(out)   :: check
    end subroutine check_particle
 
    !> Associate fields to particle
    subroutine particle_fields(w, x, E, B)
      use mod_global_parameters
      double precision, intent(in)  :: w(ixG^T,1:nw)
      double precision, intent(in)  :: x(ixG^T,1:ndim)
      double precision, intent(out) :: E(ixG^T, ndir)
      double precision, intent(out) :: B(ixG^T, ndir)
    end subroutine particle_fields
 
    subroutine particle_analytic(ix, x, tloc, vec)
      use mod_global_parameters
      integer, intent(in)           :: ix(ndir) !< Indices in gridvars
      double precision, intent(in)  :: x(ndir)
      double precision, intent(in)  :: tloc
      double precision, intent(out) :: vec(ndir)
    end subroutine particle_analytic
 
    !> User-defined particle movement
    subroutine particle_position(x, n, tloc, tlocnew)
      use mod_global_parameters
      integer, intent(in)             :: n
      double precision, intent(inout) :: x(3)
      double precision, intent(in)    :: tloc, tlocnew
    end subroutine particle_position
 
    subroutine after_refine(n_coarsen, n_refine)
      integer, intent(in) :: n_coarsen
      integer, intent(in) :: n_refine
    end subroutine after_refine
 
    !> initialize vector potential on cell edges for magnetic field
    subroutine init_vector_potential(ixI^L, ixC^L, xC, A, idir)
      use mod_global_parameters
 
      integer, intent(in)                :: ixI^L, ixC^L, idir
      double precision, intent(in)       :: xC(ixI^S,1:ndim)
      double precision, intent(out)      :: A(ixI^S)
 
    end subroutine init_vector_potential
 
    ! allow user to change inductive electric field, especially for boundary driven applications
    subroutine set_electric_field(ixI^L,ixO^L,qt,qdt,fE,s)
      use mod_global_parameters
      integer, intent(in)                :: ixI^L, ixO^L
      double precision, intent(in)       :: qt, qdt
      type(state)                        :: s
      double precision, intent(inout)    :: fE(ixI^S,sdim:3)
 
      !integer :: ixC^L,ixA^L
      ! For example, to set inductive electric field at bottom boundary in a 3D box for induction equation
      ! v and b are  from observational data for data-driven application
 
      !associate(w=>s%w,ws=>s%ws)
 
      !if(s%is_physical_boundary(5)) then
      !  ixCmin^D=ixOmin^D-1;
      !  ixCmax^D=ixOmax^D;
      !  ixAmin^D=ixCmin^D;
      !  ixAmax^D=ixCmax^D+1;
      !  fE(nghostcells^%3ixA^S,1)=-ws(nghostcells^%3ixA^S,3)*w(nghostcells^%3ixA^S,mom(2))
      !  fE(nghostcells^%3ixA^S,2)= ws(nghostcells^%3ixA^S,3)*w(nghostcells^%3ixA^S,mom(1))
      !  ixAmin^D=ixCmin^D+kr(2,^D);
      !  ixAmax^D=ixCmax^D+kr(2,^D);
      !  fE(nghostcells^%3ixC^S,1)=0.5d0*(fE(nghostcells^%3ixC^S,1)+fE(nghostcells^%3ixA^S,1))*&
      !                            qdt*s%dsC(nghostcells^%3ixC^S,1)
      !  ixAmin^D=ixCmin^D+kr(1,^D);
      !  ixAmax^D=ixCmax^D+kr(1,^D);
      !  fE(nghostcells^%3ixC^S,2)=0.5d0*(fE(nghostcells^%3ixC^S,2)+fE(nghostcells^%3ixA^S,2))*&
      !                            qdt*s%dsC(nghostcells^%3ixC^S,2)
      !end if
 
      !end associate
 
    end subroutine set_electric_field
 
    !> allow user to specify 'variables' left and right state at physical boundaries to control flux through the boundary surface
    subroutine set_wlr(ixI^L,ixO^L,qt,wLC,wRC,wLp,wRp,s,idir)
      use mod_global_parameters
      integer, intent(in)             :: ixI^L, ixO^L, idir
      double precision, intent(in)    :: qt
      double precision, intent(inout) :: wLC(ixI^S,1:nw), wRC(ixI^S,1:nw)
      double precision, intent(inout) :: wLp(ixI^S,1:nw), wRp(ixI^S,1:nw)
      type(state)                     :: s
 
      !if(s%is_physical_boundary(3).and.idir==2) then
      !  wLp(ixOmin2^%2ixO^S,mom(1))=1.d0
      !  wRp(ixOmin2^%2ixO^S,mom(1))=wRp(ixOmin2^%2ixO^S,mom(1))
      !  wLC(ixOmin2^%2ixO^S,mom(1))=wLp(ixOmin2^%2ixO^S,mom(1))*wLp(ixOmin2^%2ixO^S,rho_)
      !  wRC(ixOmin2^%2ixO^S,mom(1))=wRp(ixOmin2^%2ixO^S,mom(1))*wRp(ixOmin2^%2ixO^S,rho_)
      !end if
    end subroutine set_wlr
 
    subroutine set_surface(ixI^L,x,delx,exp_factor,del_exp_factor,exp_factor_primitive)
      use mod_global_parameters
      integer, intent(in)              :: ixI^L
      double precision, intent(in)     :: delx(ixI^S,1:ndim), x(ixI^S,1:ndim)
      double precision, intent(out)    :: exp_factor(ixI^S), del_exp_factor(ixI^S)
      double precision, intent(out)    :: exp_factor_primitive(ixI^S)
 
    end subroutine set_surface
 
    subroutine set_field_w(igrid,ip,xf,wP,wL,numP,nwP,nwL,dL,forward,ftype,tcondi)
      use mod_global_parameters
      !use mod_point_searching
 
      integer, intent(in)                 :: igrid,ip,numP,nwP,nwL
      double precision, intent(in)        :: xf(numP,ndim)
      double precision, intent(inout)     :: wP(numP,nwP),wL(1+nwL)
      double precision, intent(in)        :: dL
      logical, intent(in)                 :: forward
      character(len=std_len), intent(in)  :: ftype,tcondi
 
      !double precision :: xpp(1:ndim),wpp(1:nw)
 
      !! nwP=2,nwL=0. get rho/T at line
      !if (tcondi=='user') then
      !  xpp(1:ndim)=xf(ip,1:ndim)
      !  call get_point_w_ingrid(igrid,xpp,wpp,'primitive')
      !  wP(ip,1)=wpp(rho_)
      !  wP(ip,2)=wpp(p_)/wpp(rho_)
      !endif
 
    end subroutine set_field_w
 
    subroutine set_field(xfn,igrid,field,ftype)
      use mod_global_parameters
 
      integer,intent(in)                  :: igrid
      double precision, intent(in)        :: xfn(ndim)
      double precision, intent(inout)     :: field(ndim)
      character(len=std_len), intent(in)  :: ftype
 
      !if (ftype='xdir') then
      !  field(:)=zero
      !  field(1)=1.d0
      !endif
 
    end subroutine set_field
 
    !> Calculate volumetric heating rate for TRAC broadening
    subroutine sub_get_heating(Qgrid,ixI^L,ixO^L,w,x)
      use mod_global_parameters
      integer, intent(in)          :: ixI^L, ixO^L
      double precision, intent(in) :: x(ixI^S,1:ndim), w(ixI^S,1:nw)
      double precision, intent(out):: Qgrid(ixI^S)
    end subroutine sub_get_heating
 
  end interface
 
end module mod_usr_methods