C
C Invocation from WRAPPER level...
C
C  |
C  |-THE_MODEL_MAIN :: Primary driver for the MITgcm algorithm
C    |              :: Called from WRAPPER level numerical
C    |              :: code invocation routine. On entry
C    |              :: to THE_MODEL_MAIN separate thread and
C    |              :: separate processes will have been established.
C    |              :: Each thread and process will have a unique ID
C    |              :: but as yet it will not be associated with a
C    |              :: specific region in decomposed discrete space.
C    |
C    |-INITIALISE_FIXED :: Set fixed model arrays such as topography,
C    | |                :: grid, solver matrices etc..
C    | |
C    | |-INI_PARMS :: Routine to set kernel model parameters.
C    | |           :: Kernel parameters are read from file "data"
C    | |           :: in directory in which code executes.
C    | |
C    | |-PACKAGES_BOOT      :: Start up the optional package environment.
C    | |                    :: Runtime selection of active packages.
C    | |-PACKAGES_READPARMS :: read all packages input parameter file
C    | | |- ${PKG}_READPARMS
C    | |
C    | |-SET_PARMS :: Finalise model parameter setting (if fct of pkg usage)
C    | |
C    | |-INI_MODEL_IO  :: Initialise Input/Ouput setting
C    | |  |-MNC_INIT
C    | |  |-MNC_CW_INIT
C    | |  |
C    | |  |-MON_INIT   :: Initialises monitor pacakge ( see pkg/monitor )
C    | |
C    | |-INI_GRID      :: Control grid array (vert. and hori.) initialisation.
C    | | |             :: Grid arrays are held and described in GRID.h.
C    | | |-LOAD_GRID_SPACING        :: Load grid spacing (vector) from files
C    | | |-INI_VERTICAL_GRID        :: Set up vertical grid and coordinate
C    | | |-INI_CARTESIAN_GRID       :: Cartesian horiz. grid initialisation
C    | | |                          :: (calculate grid from kernel parameters).
C    | | |-INI_SPHERICAL_POLAR_GRID :: Spherical polar horiz. grid setting
C    | | |                          :: (calculate grid from kernel parameters).
C    | | |-INI_CURVILINEAR_GRID     :: General orthogonal, structured horiz.
C    | | |                          :: grid initialisations. ( input from raw
C    | | |                          :: grid files, LONC.bin, DXF.bin etc... )
C    | | |-INI_CYLINDER_GRID        :: Cylindrical horiz. grid setting
C    | |
C    | |-LOAD_REF_FILES   ::
C    | |-INI_EOS          ::
C    | |-SET_REF_STATE    ::
C    | |-SET_GRID_FACTORS ::
C    | |
C    | |-INI_DEPTHS    :: Read (from "bathyFile") or set bathymetry/orography.
C    | |-INI_MASKS_ETC :: Derive horizontal and vertical cell fractions and
C    | |               :: land masking for solid-fluid boundaries.
C    | |
C    | |-PACKAGES_INIT_FIXED  :: do all packages fixed-initialisation setting
C    | | |- ${PKG}_INIT_FIXED
C    | |
C    | |-INI_GLOBAL_DOMAIN
C    | |-INI_LINEAR_PHSURF :: Set ref. surface Bo_surf
C    | |
C    | |-INI_CORI          :: Set coriolis term. zero, f-plane, beta-plane,
C    | |                   :: sphere optins are coded.
C    | |-INI_CG2D          :: 2d con. grad solver initialisation.
C    | |-INI_CG3D          :: 3d con. grad solver initialisation.
C    | |
C    | |-CONFIG_SUMMARY    :: Provide synopsis of kernel setup. Includes
C    | |                   :: annotated table of kernel parameter settings.
C    | |
C    | |-PACKAGES_CHECK    :: call each package configuration checking S/R
C    | | |- ${PKG}_CHECK
C    | |
C    | |-CONFIG_CHECK      :: Check config and parameter consistency.
C    | |
C    | |-WRITE_GRID
C    | |-CPL_EXCH_CONFIGS
C    |
C    |-CTRL_UNPACK         :: Control vector support package. see pkg/ctrl
C    |-COST_DEPENDENT_INIT ::
C    |
C    |-ADTHE_MAIN_LOOP :: Derivative evaluating form of main time stepping loop
C    !                 :: Automatically generated by TAMC/TAF.
C    |
C    |-THE_MAIN_LOOP   :: Main timestepping loop routine.
C    | |
C    | |-INITIALISE_VARIA :: Set the initial conditions for time evolving
C    | | |
C #ifdef ALLOW_AUTODIFF
C    | | |-INI_DEPTHS         \
C    | | |-CTRL_DEPTH_INI      \
C    | | |-UPDATE_MASKS_ETC     } ALLOW_DEPTH_CONTROL case
C    | | |-UPDATE_CG2D         /
C #endif
C    | | |-INI_NLFS_VARS :: Initialise all Non-Lin Free-Surf arrays (SURFACE.h)
C    | | |-INI_DYNVARS   :: Initialise to zero all DYNVARS.h arrays
C    | | |-INI_NH_VARS   :: Initialise to zero all NH_VARS.h arrays
C    | | |
C    | | |-INI_FIELDS   :: Control initialising model fields to non-zero
C    | | | |-INI_VEL    :: Initialize 3D flow field.
C    | | | |-INI_THETA  :: Set model initial temperature field.
C    | | | |-INI_SALT   :: Set model initial salinity field.
C    | | | |-INI_PSURF  :: Set model initial free-surface height/pressure.
C    | | | |-READ_PICKUP
C    | | |
C    | | |-INI_MIXING   :: Initialise diapycnal diffusivity.
C    | | |-TAUEDDY_INIT_VARIA
C    | | |
C    | | |-INI_FORCING  :: initialise forcing fields
C    | | |-INI_FORCING  :: Set model initial forcing fields.
C    | | |   |          :: Either set in-line or from file as shown.
C    | | |   |-READ_FLD_XY_RS(zonalWindFile)
C    | | |   |-READ_FLD_XY_RS(meridWindFile)
C    | | |   |-READ_FLD_XY_RS(surfQnetFile)
C    | | |   |-READ_FLD_XY_RS(EmPmRfile)
C    | | |   |-READ_FLD_XY_RS(thetaClimFile)
C    | | |   |-READ_FLD_XY_RS(saltClimFile)
C    | | |   |-READ_FLD_XY_RS(surfQswFile)
C    | | |
C    | | |-AUTODIFF_INIT_VARIA
C    | | |
C    | | |-PACKAGES_INIT_VARIABLES :: Does initialisation of time evolving
C    | | | | ${PKG}_INIT_VARIA     :: package data.
C    | | |
C    | | |-COST_INIT_VARIA
C    | | |-CONVECTIVE_ADJUSTMENT_INI
C    | | |
C    | | |-CALC_R_STAR    :: Calculate the new level thickness factor (r* coord)
C    | | |-UPDATE_R_STAR  :: Update the level thickness fraction (r* coord).
C    | | |-UPDATE_SIGMA   :: Update the level thickness fraction (sigma-coord).
C    | | |-CALC_SURF_DR   :: Calculate the new surface level thickness.
C    | | |-UPDATE_SURF_DR :: Update the surface-level thickness fraction.
C    | | |
C    | | |-UPDATE_CG2D    :: Update 2d conjugate grad. for Free-Surf.
C    | | |
C    | | |-INTEGR_CONTINUITY :: Integrate the continuity Eqiuation
C    | | | |-INTEGRATE_FOR_W :: Integrate for vertical velocity
C    | | | |-OBCS_APPLY_W    :: Open boundary package (see pkg/obcs).
C    | | | |-UPDATE_ETAH     :: Update Surface height/pressure
C    | | |
C    | | |-CALC_R_STAR    :: Calculate the new level thickness factor (r* coord)
C    | | |-CALC_SURF_DR   :: Calculate the new surface level thickness.
C    | | |
C    | | |-STATE_SUMMARY    :: Summarise model prognostic variables.
C    | | |
C    | | |-MONITOR          :: Monitor state (see pkg/monitor)
C    | | |
C    | | |-DO_STATEVARS_TAVE :: Time averaging package ( see pkg/timeave ).
C    | | |  |-TIMEAVE_STATVARS ::
C    | | |  |-PTRACERS_TIMEAVE ::
C    | | |
C    | | |-DO_THE_MODEL_IO  :: Controlling routine for IO
C    | | | |-WRITE_STATE    ::  Write model state variables.
C    | | | |-TIMEAVE_STATV_WRITE :: Write Time averaged output (see pkg/timeave)
C    | | | |-FIZHI_WRITE_STATE
C    | | | |-AIM_WRITE_TAVE
C    | | | |-LAND_OUTPUT
C    | | | |-OBCS_OUTPUT
C    | | | |-GMREDI_OUTPUT
C    | | | |-KPP_OUTPUT
C    | | | |-PP81_OUTPUT
C    | | | |-KL10_OUTPUT
C    | | | |-MY82_OUTPUT
C    | | | |-OPPS_OUTPUT
C    | | | |-GGL90_OUTPUT
C    | | | |-SBO_CALC
C    | | | |-SBO_OUTPUT
C    | | | |-SEAICE_OUTPUT
C    | | | |-SHELFICE_OUTPUT
C    | | | |-BULKF_OUTPUT
C    | | | |-THSICE_OUTPUT
C    | | | |-PTRACERS_OUTPUT
C    | | | |-MATRIX_OUTPUT
C    | | | |-GCHEM_OUTPUT
C    | | | |-CPL_OUTPUT
C    | | | |-LAYERS_CALC
C    | | | |-LAYERS_OUTPUT
C    | | | |-DIAGNOSTICS_WRITE :: Write pkg/diagnostics output
C    | | |
C====|>| ****************************
C====|>| BEGIN MAIN TIMESTEPPING LOOP
C====|>| ****************************
C    | |-COST_AVERAGESFIELDS :: time-averaged Cost function terms (see pkg/cost)
C    | |-PROFILES_INLOOP     ::
C    | /
C    | |-MAIN_DO_LOOP    :: Open-AD case: Main timestepping loop routine
C    | \                    otherwise: just call FORWARD_STEP
C    | |
C/\  | |-FORWARD_STEP        :: Step forward a time-step ( AT LAST !!! )
C/\  | | |
C/\  | | |-LOAD_FIELDS_DRIVER :: control loading of input fields from files
C/\  | | |
C/\  | | |-CTRL_MAP_FORCING   :: Control vector support package. (see pkg/ctrl)
C/\  | | |
C/\  | | |-CPL_EXPORT_MY_DATA :: Send coupling fields to coupler
C/\  | | |-CPL_IMPORT_EXTERNAL_DATA :: Receive coupling fields from coupler
C/\  | | |
C/\  | | |-DO_ATMOSPHERIC_PHYS :: Atmospheric physics computation
C/\  | | |
C/\  | | |-DO_OCEANIC_PHYS     :: Oceanic (& seaice) physics computation
C/\  | | | |-OBCS_CALC         :: Open boundary. package (see pkg/obcs).
C/\  | | | |-EXTERNAL_FORCING_SURF:: Accumulates appropriately dimensioned
C/\  | | | |                      :: forcing terms.
C/\  | | |
C/\  | | |-GCHEM_CALC_TENDENCY :: geochemistry driver routine (see pkg/gchem)
C/\  | | |
C/\  | | |-THERMODYNAMICS      :: (synchronous time-stepping)
C/\  | | |                        theta, salt + tracer equations driver.
C/\  | | | |-GMREDI_RESIDUAL_FLOW :: Get the flow field used to advect tracer
C/\  | | | |
C/\  | | | |-TEMP_INTEGRATE       :: Step forward Prognostic Eq for Temperature.
C/\  | | | | |-GAD_ADVECTION      :: Generalised advection driver (multi-dim
C/\  | | | | |                         advection case) (see pkg/gad).
C/\  | | | | |-GAD_CALC_RHS       :: Calculate Advection-Diffusion tendency terms
C/\  | | | | |-TIMESTEP_TRACER    :: Step tracer field forward in time
C/\  | | | | |-IMPLDIFF           :: Solve vertical implicit diffusion equation.
C/\  | | | | |-CYCLE_AB_TRACER    :: Cycle time-stepping arrays for tracer field
C/\  | | | |
C/\  | | | |-SALT_INTEGRATE       :: Step forward Prognostic Eq for Salinity.
C/\  | | | | |                       same sequence of calls as in TEMP_INTEGRATE
C/\  | | | |
C/\  | | | |-PTRACERS_INTEGRATE   :: Integrate other tracer(s) (see pkg/ptracers).
C/\  | | | | |                       same sequence of calls as in TEMP_INTEGRATE
C/\  | | | | |-OBCS_APPLY_PTRACER :: Open boundary package for pTracers
C/\  | | | |
C/\  | | | |-OBCS_APPLY_TS        :: Open boundary package (see pkg/obcs ).
C/\  | | |
C/\  | | |-DYNAMICS       :: Momentum equations driver.
C/\  | | | |
C/\  | | | |-CALC_GRAD_PHI_SURF :: Calculate the gradient of the surface
C/\  | | | |                       Potential anomaly.
C/\  | | | |-CALC_VISCOSITY   :: Calculate net vertical viscosity
C/\  | | | |-CALC_PHI_HYD     :: Integrate the hydrostatic relation.
C/\  | | | |-MOM_FLUXFORM     :: Flux form mom eqn. package  (pkg/mom_fluxform)
C/\  | | | |-MOM_VECINV       :: Vector invariant form mom eqn (pkg/mom_vecinv)
C/\  | | | |-TIMESTEP         :: Step momentum fields forward in time
C/\  | | | |-OBCS_APPLY_UV    :: Open boundary package (see pkg/obcs).
C/\  | | | |-IMPLDIFF         :: Solve vertical implicit diffusion equation.
C/\  | | | |-CALC_GW          :: vert. momentum tendency terms (Non-Hydrostatic)
C/\  | | |
C/\  | | |-UPDATE_SURF_DR :: Update the surface-level thickness fraction.
C/\  | | |-UPDATE_R_STAR  :: Update the level thickness fraction.
C/\  | | |-UPDATE_CG2D    :: Update 2d conjugate grad. for Free-Surf.
C/\  | | |
C/\  | | |-SOLVE_FOR_PRESSURE  :: Find surface pressure.
C/\  | | | |-CG2D              :: Two-dim pre-con. conjugate-gradient.
C/\  | | | |-CG3D              :: Three-dim pre-con. conjugate-gradient solver.
C/\  | | |
C/\  | | |-MOMENTUM_CORRECTION_STEP :: Finalise momentum stepping
C/\  | | | |-CALC_GRAD_PHI_SURF :: Return DDx and DDy of surface pressure
C/\  | | | |-CORRECTION_STEP    :: Pressure correction to momentum
C/\  | | | |-OBCS_APPLY_UV      :: Open boundary package (see pkg/obcs).
C/\  | | |
C/\  | | |-INTEGR_CONTINUITY    :: Integrate continuity equation
C/\  | | |
C/\  | | |-THERMODYNAMICS       :: (staggered time-stepping)
C/\  | | |                         theta, salt + tracer equations driver.
C/\  | | |
C/\  | | |-TRACERS_CORRECTION_STEP :: Finalise tracer steppin:
C/\  | | |                             apply filter, conv.adjustment
C/\  | | |
C/\  | | |-GCHEM_FORCING_SEP :: tracer forcing for gchem pkg (if tracer
C/\  | | |                      dependent tendencies calculated separately)
C/\  | | |
C/\  | | |-DO_FIELDS_BLOCKING_EXCHANGES :: Sync up overlap regions.
C/\  | | |
C/\  | | |-MONITOR          :: Monitor package (pkg/monitor).
C/\  | | |-DO_THE_MODEL_IO  :: Standard diagnostic I/O.
C/\  | | |
C/\  | | |-DO_WRITE_PICKUP  :: Write restart files.
C    | |
C<===|=| **************************
C<===|=| END MAIN TIMESTEPPING LOOP
C<===|=| **************************
C    | |
C    | |-COST_AVERAGESFIELDS :: time-averaged Cost function terms (see pkg/cost)
C    | |-PROFILES_INLOOP     ::
C    | |-COST_FINAL          :: Cost function package. (see pkg/cost)
C    |
C    |-CTRL_PACK       :: Control vector support package. see pkg/ctrl
C    |
C    |-GRDCHK_MAIN     :: Gradient check package. see pkg/grdchk
C    |
C    |-TIMER_PRINTALL  :: Computational timing summary
C    |
C    |-COMM_STATS      :: Summarise inter-proc and inter-thread communication
C                      :: events.