feat(codegen): auto-generate array declarations via FORTRAN_ARRAY_DIMS

Adds fortran_dim support for indexed-family array parameters.
fluid_rho (pre) and 9 output arrays (post) no longer need manual
Fortran declarations — all are generated from definitions.py.

Remaining manual declarations are exclusively Fortran derived-type
variables (bc_x, fluid_pp, patch_icpp, etc.) which require
type information that lives in m_derived_types.fpp.

Author: sbryngelson

src/post_process/m_global_parameters.fpp

@@ -135,24 +135,10 @@ module m_global_parameters
     type(int_bounds_info) :: offset_x, offset_y, offset_z
     !> @}
 
-    !> @name The list of all possible flow variables that may be written to a database file. It includes partial densities, density,
-    !! momentum, velocity, energy, pressure, volume fraction(s), specific heat ratio function, specific heat ratio, liquid stiffness
-    !! function, liquid stiffness, primitive variables, conservative variables, speed of sound, the vorticity, and the numerical
-    !! Schlieren function.
-    !> @{
-    logical, dimension(num_fluids_max) :: alpha_rho_wrt
-    logical, dimension(3)              :: mom_wrt
-    logical, dimension(3)              :: vel_wrt
-    logical, dimension(3)              :: flux_wrt
-    logical, dimension(num_fluids_max) :: alpha_rho_e_wrt
-    logical, dimension(num_fluids_max) :: alpha_wrt
-    logical, dimension(3)              :: omega_wrt
-    logical                            :: chem_wrt_Y(1:num_species)
-    !> @}
-
-    real(wp), dimension(num_fluids_max) :: schlieren_alpha  !< Per-fluid Schlieren intensity amplitude coefficients
-    integer                             :: fd_number        !< Finite-difference half-stencil size: MAX(1, fd_order/2)
-    type(chemistry_parameters)          :: chem_params
+    ! alpha_rho_wrt, mom_wrt, vel_wrt, flux_wrt, alpha_rho_e_wrt, alpha_wrt,
+    ! omega_wrt, chem_wrt_Y, schlieren_alpha: auto-generated in generated_decls.fpp
+    integer                    :: fd_number  !< Finite-difference half-stencil size: MAX(1, fd_order/2)
+    type(chemistry_parameters) :: chem_params
     !> @name Bubble modeling variables and parameters
     !> @{
     real(wp) :: Eu

src/pre_process/m_global_parameters.fpp

@@ -65,10 +65,9 @@ module m_global_parameters
     integer, dimension(3, 2)   :: shear_BC_flip_indices  !< Shear stress BC reflection indices (1:3, 1:shear_BC_flip_num)
     type(simplex_noise_params) :: simplex_params
 
-    ! Perturb density of surrounding air so as to break symmetry of grid
-    real(wp), dimension(num_fluids_max) :: fluid_rho
-    integer, allocatable, dimension(:)  :: proc_coords  !< Processor coordinates in MPI_CART_COMM
-    integer, allocatable, dimension(:)  :: start_idx    !< Starting cell-center index of local processor in global grid
+    ! Perturb density of surrounding air so as to break symmetry of grid fluid_rho: auto-generated in generated_decls.fpp
+    integer, allocatable, dimension(:) :: proc_coords  !< Processor coordinates in MPI_CART_COMM
+    integer, allocatable, dimension(:) :: start_idx    !< Starting cell-center index of local processor in global grid
 #ifdef MFC_MPI
     type(mpi_io_var), public :: MPI_IO_DATA
     character(LEN=name_len)  :: mpiiofs

toolchain/mfc/params/definitions.py

@@ -1029,6 +1029,22 @@ def _init_registry():
 
 NAMELIST_VARS: dict[str, set[str]] = {}
 
+# Maps indexed-family base names to their Fortran dimension expression.
+# The generator emits `{type}, dimension({dim}) :: {name}` for each entry.
+# Add here whenever a new array param needs no manual Fortran declaration.
+FORTRAN_ARRAY_DIMS: dict[str, str] = {
+    "fluid_rho": "num_fluids_max",  # pre
+    "alpha_rho_wrt": "num_fluids_max",  # post
+    "alpha_rho_e_wrt": "num_fluids_max",  # post
+    "alpha_wrt": "num_fluids_max",  # post
+    "schlieren_alpha": "num_fluids_max",  # post
+    "chem_wrt_Y": "num_species",  # post (imported from m_thermochem)
+    "flux_wrt": "3",  # post
+    "mom_wrt": "3",  # post
+    "omega_wrt": "3",  # post
+    "vel_wrt": "3",  # post
+}
+
 
 def _nv(targets: set, *names: str) -> None:
     for n in names:

toolchain/mfc/params/generators/fortran_gen.py

@@ -3,7 +3,7 @@
 from pathlib import Path
 from typing import List, Tuple
 
-from ..definitions import CASE_OPT_PARAMS, NAMELIST_VARS  # noqa: F401 - triggers registry population
+from ..definitions import CASE_OPT_PARAMS, FORTRAN_ARRAY_DIMS, NAMELIST_VARS  # noqa: F401 - triggers registry population
 from ..registry import REGISTRY
 from ..schema import ParamDef, ParamType
 
@@ -15,7 +15,8 @@
 _FIRST_PREFIX = "namelist /user_inputs/ "
 _CONT_PREFIX = "    & "
 _CONT2_PREFIX = "        & "  # inside #:if block
-_DECL_COL = 24  # '::' column, matches ffmt alignment
+_DECL_COL = 24  # '::' column for scalars, matches ffmt alignment
+_ARRAY_DECL_COL = 36  # '::' column for array decls
 
 _FORTRAN_TYPES = {
     ParamType.INT: "integer",
@@ -98,20 +99,24 @@ def generate_namelist_fpp(target: str) -> str:
 
 
 def generate_decls_fpp(target: str) -> str:
-    """Return simple scalar Fortran declarations for a target as a string."""
+    """Return Fortran declarations (scalars + known arrays) for a target."""
     assert target in ("pre", "sim", "post")
     lines = [_HEADER.rstrip()]
     for name in _vars_for_target(target):
         if not _is_simple_scalar(name):
             continue
-        # Skip sim case-opt params: declared as compile-time parameters by the
-        # manual #:if MFC_CASE_OPTIMIZATION / #:else block in m_global_parameters.fpp
         if target == "sim" and name in CASE_OPT_PARAMS:
             continue
+        if name in FORTRAN_ARRAY_DIMS:
+            member = REGISTRY.all_params.get(f"{name}(1)")
+            if member is not None:
+                ftype = fortran_type_decl(member)
+                dim = FORTRAN_ARRAY_DIMS[name]
+                lines.append(f"{(ftype + ', dimension(' + dim + ')').ljust(_ARRAY_DECL_COL)}:: {name}")
+            continue
         param = REGISTRY.all_params.get(name)
         if param is None:
             continue
-        # Skip if also registered as an indexed family — Fortran declares it as an array.
         if any(k.startswith(f"{name}(") for k in REGISTRY.all_params):
             continue
         lines.append(f"{fortran_type_decl(param).ljust(_DECL_COL)}:: {name}")