grid_enum.h

#pragma once
 
// An enum which holds offsets for grid quantities
// In the final form of this approach, this file will also set nfields (not yet)
// and NSCALARS (done) so that adding a field only requires registering it here:
// grid knows to allocate memory based on nfields and NSCALARS
// and values can be accessed with density[id + ncells*grid_enum::enum_name]
// example: C.device[id + H.n_cells*grid_enum::basic_scalar]
 
// enum notes:
// For advanced devs: to be implicitly treated as int,
// The enum cannot use "enum class" or "enum struct."
// This is referred to as an "unscoped enum:" grid_enum is "unscoped"
// Though we give it an effective scope by wrapping it in a namespace.
 
// Enum is wrapped in namespace to give
// it an effective scope to prevent collisions.
 
// Enum values (i.e. density) belong
// to their enclosing scope, which necessitates the namespace wrapping
// --otherwise "density" would be available in global scope.
 
// The ": int" forces underlying type to be int.
 
// if you update this enum, make sure that you also update the pack_arr_ variable from
// field_info.cpp
 
namespace grid_enum
{
enum : int {
 
  // Don't change order of hydro quantities until all of hydro is made
  // consistent with grid_enum (if ever) because enum values depend on order
  density,
  momentum_x,
  momentum_y,
  momentum_z,
  Energy,
 
  // Code assumes scalars are a contiguous block
  // Always define scalar, scalar_minus_1, finalscalar_plus_1, finalscalar to
  // compute NSCALARS
  scalar,
  scalar_minus_1 = scalar - 1,  // so that next enum item starts at same index as scalar
 
#ifdef SCALAR
  // Add scalars here, wrapped appropriately with ifdefs:
  #ifdef BASIC_SCALAR
  basic_scalar,
  #endif
 
  #if defined(COOLING_GRACKLE) || defined(CHEMISTRY_GPU)
  HI_density,
  HII_density,
  HeI_density,
  HeII_density,
  HeIII_density,
  e_density,
    #ifdef GRACKLE_METALS
  metal_density,
    #endif
  #endif
 
  #ifdef DUST
  dust_density,
  #endif  // DUST
 
#endif  // SCALAR
 
  finalscalar_plus_1,                    // needed to calculate NSCALARS
  finalscalar = finalscalar_plus_1 - 1,  // resets enum to finalscalar so fields afterwards are correct
// so that anything after starts with scalar + NSCALARS
 
#ifdef MHD
  magnetic_x,
  magnetic_y,
  magnetic_z,
#endif
#ifdef DE
  GasEnergy,
#endif
  num_fields,
 
  // Aliases and manually computed enums
  nscalars = finalscalar_plus_1 - scalar,
 
#ifdef MHD
  num_flux_fields      = num_fields - 1,
  num_interface_fields = num_fields - 1,
#else
  num_flux_fields      = num_fields,
  num_interface_fields = num_fields,
#endif  // MHD
 
#ifdef MHD
  magnetic_start = magnetic_x,
  magnetic_end   = magnetic_z,
 
  ct_elec_x = 0,
  ct_elec_y = 1,
  ct_elec_z = 2,
 
  // Note that the direction of the flux, the suffix _? indicates the direction
  // of the electric field, not the magnetic flux
  fluxX_magnetic_z = magnetic_start,
  fluxX_magnetic_y = magnetic_start + 1,
  fluxY_magnetic_x = magnetic_start,
  fluxY_magnetic_z = magnetic_start + 1,
  fluxZ_magnetic_y = magnetic_start,
  fluxZ_magnetic_x = magnetic_start + 1,
 
  Q_x_magnetic_y = magnetic_start,
  Q_x_magnetic_z = magnetic_start + 1,
  Q_y_magnetic_z = magnetic_start,
  Q_y_magnetic_x = magnetic_start + 1,
  Q_z_magnetic_x = magnetic_start,
  Q_z_magnetic_y = magnetic_start + 1
#endif  // MHD
 
};
}  // namespace grid_enum
 
#define NSCALARS grid_enum::nscalars