From 8db64f8c4721a045b3c4040b7a7f4ba3d8303efd Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 14:50:38 +0100
Subject: [PATCH 01/13] Rename `IPNVARS` to `N_ITERATION_VARIABLES_MAX` for
 consistency with style guide

---
 process/core/input.py              |  4 +--
 process/data_structure/numerics.py | 50 +++++++++++++++++++++---------
 2 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/process/core/input.py b/process/core/input.py
index 93886b8a16..d03a87c9b2 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -15,7 +15,7 @@
 )
 from process.core.solver.constraints import ConstraintManager
 from process.data_structure.impurity_radiation_variables import N_IMPURITIES
-from process.data_structure.numerics import IPNVARS
+from process.data_structure.numerics import N_ITERATION_VARIABLES_MAX
 from process.data_structure.pfcoil_variables import N_PF_GROUPS_MAX
 from process.data_structure.physics_variables import N_CONFINEMENT_SCALINGS
 from process.data_structure.scan_variables import IPNSCNS, IPNSCNV
@@ -1160,7 +1160,7 @@ def bounds(self) -> tuple[NumberType | None, NumberType | None]:
     "ixc": InputVariable(
         None,
         int,
-        range=(1, IPNVARS),
+        range=(1, N_ITERATION_VARIABLES_MAX),
         additional_actions=_ixc_additional_actions,
         set_variable=False,
     ),
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 57505f1c39..6ebbd72e05 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -135,7 +135,7 @@ def description(self):
         return self._description_
 
 
-IPNVARS = max(ITERATION_VARIABLES.keys())
+N_ITERATION_VARIABLES_MAX = max(ITERATION_VARIABLES.keys())
 """total number of variables available for iteration"""
 
 # Set to a really large number so that it should never need to be changed
@@ -391,12 +391,14 @@ class NumericsData:
     * (92) D/T/He3 ratio in fuel sums to 1
     """
 
-    ixc: list[int] = field(default_factory=lambda: np.array([0] * IPNVARS))
+    ixc: list[int] = field(
+        default_factory=lambda: np.array([0] * N_ITERATION_VARIABLES_MAX)
+    )
     """Array defining which iteration variables to activate
     (see lablxc for descriptions)
     """
 
-    lablxc: list[str] = field(default_factory=lambda: [""] * IPNVARS)
+    lablxc: list[str] = field(default_factory=lambda: [""] * N_ITERATION_VARIABLES_MAX)
     """Labels describing iteration variables<UL>
     * ( 1) aspect
     * ( 2) b_plasma_toroidal_on_axis
@@ -577,7 +579,7 @@ class NumericsData:
     # WARNING These labels are used as variable names by new_indat(), and possibly
     # other python utilities, so they cannot easily be changed.
 
-    name_xc: list[str] = field(default_factory=lambda: [""] * IPNVARS)
+    name_xc: list[str] = field(default_factory=lambda: [""] * N_ITERATION_VARIABLES_MAX)
 
     sqsumsq: float = 0.0
     """sqrt of the sum of the square of the constraint residuals"""
@@ -594,43 +596,61 @@ class NumericsData:
     epsvmc: float = 1.0e-6
     """Error tolerance for optimiser"""
 
-    boundl: list[float] = field(default_factory=lambda: np.array([9.0e-99] * IPNVARS))
+    boundl: list[float] = field(
+        default_factory=lambda: np.array([9.0e-99] * N_ITERATION_VARIABLES_MAX)
+    )
     """Lower bounds used on ixc variables during
     optimisation runs
     """
 
-    boundu: list[float] = field(default_factory=lambda: np.array([9.0e99] * IPNVARS))
+    boundu: list[float] = field(
+        default_factory=lambda: np.array([9.0e99] * N_ITERATION_VARIABLES_MAX)
+    )
     """Upper bounds used on ixc variables"""
 
     itv_scaled_lower_bounds: list[float] = field(
-        default_factory=lambda: np.array([0.0] * IPNVARS)
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
     )
     """Lower bound of the ixc variables scaled to (divided by)
     the initial value of the corresponding ixc
     """
 
     itv_scaled_upper_bounds: list[float] = field(
-        default_factory=lambda: np.array([0.0] * IPNVARS)
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
     )
     """Upper bound of the ixc variables scaled to (divided by)
     the initial value of the corresponding ixc
     """
 
-    rcm: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    rcm: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
 
-    resdl: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    resdl: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
 
-    scafc: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    scafc: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
     """The initial value of each ixc variable"""
 
-    scale: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    scale: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
     """The reciprocal of the initial value of each ixc variable"""
 
-    xcm: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    xcm: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
 
-    xcs: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    xcs: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
 
-    vlam: list[float] = field(default_factory=lambda: np.array([0.0] * IPNVARS))
+    vlam: list[float] = field(
+        default_factory=lambda: np.array([0.0] * N_ITERATION_VARIABLES_MAX)
+    )
 
     force_vmcon_inequality_satisfication: int = 1
     """If 1, adds an additional convergence criteria to the VMCON solver

From d1bc23dcc0106a3b45444c80b90fd362218d971d Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 14:51:56 +0100
Subject: [PATCH 02/13] Rename `IPEQNS` to `N_CONSTRAINT_EQUATIONS_MAX` for
 consistency with style guide

---
 process/data_structure/numerics.py | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 6ebbd72e05..9bc4baddc3 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -139,7 +139,7 @@ def description(self):
 """total number of variables available for iteration"""
 
 # Set to a really large number so that it should never need to be changed
-IPEQNS = 500
+N_CONSTRAINT_EQUATIONS_MAX = 500
 """Maximum number of constraint equations available"""
 
 
@@ -185,9 +185,13 @@ class NumericsData:
     nviter: int = 0
     """number of optimisation iterations performed"""
 
-    icc: list[int] = field(default_factory=lambda: np.array([0] * IPEQNS))
+    icc: list[int] = field(
+        default_factory=lambda: np.array([0] * N_CONSTRAINT_EQUATIONS_MAX)
+    )
 
-    active_constraints: list[bool] = field(default_factory=lambda: [False] * IPEQNS)
+    active_constraints: list[bool] = field(
+        default_factory=lambda: [False] * N_CONSTRAINT_EQUATIONS_MAX
+    )
     """Logical array showing which constraints are active"""
 
     # TODO Do not change the comments for lablcc: they are used to create the

From 1d36c91f57ff92bd6dfd93343313eeddb304cffe Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 14:57:47 +0100
Subject: [PATCH 03/13] Rename `ioptimz` to `i_process_run_mode` for
 consistency with style guide

---
 documentation/source/io/input-guide.md              |  2 +-
 documentation/source/solver/solver-guide.md         |  6 +++---
 documentation/source/usage/running-process.md       |  8 ++++----
 examples/data/large_tokamak_eval_IN.DAT             |  2 +-
 process/core/init.py                                | 13 ++++++++-----
 process/core/input.py                               |  2 +-
 process/core/io/in_dat/base.py                      | 12 ++++++------
 process/core/io/plot/summary.py                     |  2 +-
 process/data_structure/numerics.py                  |  4 ++--
 process/main.py                                     | 10 ++++++----
 process/models/physics/l_h_transition.py            |  2 +-
 process/models/power.py                             |  2 +-
 tests/integration/data/large_tokamak_eval.IN.DAT    |  2 +-
 tests/regression/input_files/helias_5b.IN.DAT       |  2 +-
 .../input_files/large_tokamak_eval.IN.DAT           |  2 +-
 .../input_files/low_aspect_ratio_DEMO.IN.DAT        |  2 +-
 .../input_files/spherical_tokamak_eval.IN.DAT       |  2 +-
 tests/regression/input_files/st_regression.IN.DAT   |  2 +-
 .../input_files/stellarator_helias.IN.DAT           |  2 +-
 tests/regression/test_process_input_files.py        |  2 +-
 tests/unit/core/test_input.py                       |  6 +++---
 tests/unit/models/test_power.py                     | 10 ++++++----
 22 files changed, 52 insertions(+), 45 deletions(-)

diff --git a/documentation/source/io/input-guide.md b/documentation/source/io/input-guide.md
index b2eb4ee2a4..388f36a1b0 100644
--- a/documentation/source/io/input-guide.md
+++ b/documentation/source/io/input-guide.md
@@ -111,7 +111,7 @@ If bounds are not specified default values are used.
 The user can select which solver to use, but only one solver is available at present (VMCON).
 
 ```
-ioptimz  = 1 * for optimisation VMCON only
+i_process_run_mode  = 1 * for optimisation VMCON only
 ```
 
 The user can select the figure of merit to be used:
diff --git a/documentation/source/solver/solver-guide.md b/documentation/source/solver/solver-guide.md
index 361cd43017..9173f205f8 100644
--- a/documentation/source/solver/solver-guide.md
+++ b/documentation/source/solver/solver-guide.md
@@ -106,9 +106,9 @@ maximised figure of merit is desired, `minmax` should be **negative**.
 
 ## Optimisation mode
 
-Switch `ioptimz` should be set to 1 for optimisation mode.
+Switch `i_process_run_mode` should be set to 1 for optimisation mode.
 
-If `ioptimz = 0`, a non-optimisation pass is performed first. Occasionally this provides a feasible set of initial conditions that aids convergence of the optimiser, but it is recommended to use `ioptimz = 1`.
+If `i_process_run_mode = 0`, a non-optimisation pass is performed first. Occasionally this provides a feasible set of initial conditions that aids convergence of the optimiser, but it is recommended to use `i_process_run_mode = 1`.
 
 Enable all the relevant consistency equations, and it is advisable to enable the corresponding iterations variables. A number of limit equations (inequality constraints) can also be activated. In optimisation mode, the number of iteration variables is unlimited.
 
@@ -137,7 +137,7 @@ Running `PROCESS` in evaluation mode requires few changes to be made to the inpu
 As before, the user must decide which constraint equations and iteration variables to activate. For example, an extract from an input file might look like:
 ```
 * Evaluation problem: evaluate models consistently by solving equality constraints only
-ioptimz  = -2 * evaluation mode
+i_process_run_mode  = -2 * evaluation mode
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
diff --git a/documentation/source/usage/running-process.md b/documentation/source/usage/running-process.md
index c7c7143956..aee845060a 100644
--- a/documentation/source/usage/running-process.md
+++ b/documentation/source/usage/running-process.md
@@ -1,12 +1,12 @@
 # Running PROCESS
 
-There are a number of ways to run PROCESS.  The first two are determined by the value of the switch `ioptimz` in the input file:
+There are a number of ways to run PROCESS.  The first two are determined by the value of the switch `i_process_run_mode` in the input file:
 
-`ioptimz = -2` for evaluation. The physics and engineering models are evaluated and the equality (e.g. model consistency) constraints will be solved using `scipy`'s `fsolve`. The input file and default values together define the input values of all variables. The values of the parameters used to solve the equalities (solution parameters) will be different in the solution, however. This is used when evaluating a set of input parameters (e.g. a "point") whilst ensuring that the models are self-consistent.
+`i_process_run_mode = -2` for evaluation. The physics and engineering models are evaluated and the equality (e.g. model consistency) constraints will be solved using `scipy`'s `fsolve`. The input file and default values together define the input values of all variables. The values of the parameters used to solve the equalities (solution parameters) will be different in the solution, however. This is used when evaluating a set of input parameters (e.g. a "point") whilst ensuring that the models are self-consistent.
 
-`ioptimz = 1` for optimisation.  Those variables specified as iteration variables (specified by equations such as `ixc = 1` in the input file) are automatically varied during the iteration process, between the bounds given by the arrays `boundl` (lower bounds) and `boundu` (upper bounds).  The input file contains the *initial* values of the iteration variables, but the final values will not be same.  The iteration process continues until convergence, or until the maximum number of iterations (`maxcal`) is reached.  If the code converges, the constraints will be satisfied and the Figure of Merit will be maximised or minimised. 
+`i_process_run_mode = 1` for optimisation.  Those variables specified as iteration variables (specified by equations such as `ixc = 1` in the input file) are automatically varied during the iteration process, between the bounds given by the arrays `boundl` (lower bounds) and `boundu` (upper bounds).  The input file contains the *initial* values of the iteration variables, but the final values will not be same.  The iteration process continues until convergence, or until the maximum number of iterations (`maxcal`) is reached.  If the code converges, the constraints will be satisfied and the Figure of Merit will be maximised or minimised. 
 
-If the optimisation fails to converge, a third option is available by using the command line option `-v` (VaryRun), together with a configuration file.  PROCESS is run repeatedly in optimisation mode (`ioptimz` = 1 must be set), but a new input file is written each time, with different, randomly selected *initial* values of the iteration variables.  The factor within which the initial values of the iteration variables are changed is `FACTOR` (in the configuration file).  For example, `FACTOR = 1.1` will vary the initial values randomly by up to 10%.  This is repeated until PROCESS converges, or until the maximum number of PROCESS runs (`NITER`) is reached.  Sometimes this procedure will generate a converged solution when a single optimisation run does not.
+If the optimisation fails to converge, a third option is available by using the command line option `-v` (VaryRun), together with a configuration file.  PROCESS is run repeatedly in optimisation mode (`i_process_run_mode` = 1 must be set), but a new input file is written each time, with different, randomly selected *initial* values of the iteration variables.  The factor within which the initial values of the iteration variables are changed is `FACTOR` (in the configuration file).  For example, `FACTOR = 1.1` will vary the initial values randomly by up to 10%.  This is repeated until PROCESS converges, or until the maximum number of PROCESS runs (`NITER`) is reached.  Sometimes this procedure will generate a converged solution when a single optimisation run does not.
 
 A SCAN is available in any of these modes.  One input variable can be scanned (`scan_dim = 1`) or two input variables (`scan_dim = 2`).  A scan variable must not be an iteration variable.  For details, see ScanVariables in the [scan module](../../source/reference/process/scan).
 
diff --git a/examples/data/large_tokamak_eval_IN.DAT b/examples/data/large_tokamak_eval_IN.DAT
index 80b3369813..1b81c32a2d 100644
--- a/examples/data/large_tokamak_eval_IN.DAT
+++ b/examples/data/large_tokamak_eval_IN.DAT
@@ -1,5 +1,5 @@
 * Evaluation problem: evaluate models consistently by solving equality constraints only
-ioptimz  = -2
+i_process_run_mode  = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
diff --git a/process/core/init.py b/process/core/init.py
index 1b7e6dc508..9c22d0b3bc 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -185,7 +185,7 @@ def run_summary(data: DataStructure):
         )
         process_output.ocmmnt(outfile, f"Iteration variables : {data.numerics.nvar}")
         # If optimising, write objective function and convergence parameter
-        if data.numerics.ioptimz == PROCESSRunMode.OPTIMISATION:
+        if data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION:
             process_output.ocmmnt(
                 outfile,
                 f"Max iterations : {data.globals.maxcal}",
@@ -227,10 +227,13 @@ def run_summary(data: DataStructure):
     process_output.ovarre(mfile, "Input filename", "(fileprefix)", f'"{fileprefix}"')
 
     process_output.ovarre(
-        mfile, "Optimisation switch", "(ioptimz)", data.numerics.ioptimz
+        mfile,
+        "Optimisation switch",
+        "(i_process_run_mode)",
+        data.numerics.i_process_run_mode,
     )
     # If optimising, write figure of merit switch
-    if data.numerics.ioptimz == PROCESSRunMode.OPTIMISATION:
+    if data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION:
         process_output.ovarre(
             mfile, "Figure of merit switch", "(minmax)", data.numerics.minmax
         )
@@ -414,7 +417,7 @@ def check_process(inputs, data):  # noqa: ARG001
             )
 
         if (
-            data.numerics.ioptimz == PROCESSRunMode.OPTIMISATION
+            data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION
             and (data.numerics.ixc[: data.numerics.nvar] == 4).any()
             and data.numerics.boundl[3] < data.physics.temp_plasma_pedestal_kev * 1.001
         ):
@@ -488,7 +491,7 @@ def check_process(inputs, data):  # noqa: ARG001
         # (nd_plasma_electron_on_axis>nd_plasma_pedestal_electron)
         #  -> Potential hollowed density profile
         if (
-            data.numerics.ioptimz == PROCESSRunMode.OPTIMISATION
+            data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION
             and not (
                 data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 81
             ).any()
diff --git a/process/core/input.py b/process/core/input.py
index d03a87c9b2..0fba32c17d 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -146,7 +146,7 @@ def bounds(self) -> tuple[NumberType | None, NumberType | None]:
 
 INPUT_VARIABLES = {
     "runtitle": InputVariable("globals", str),
-    "ioptimz": InputVariable("numerics", int, choices=[1, -2]),
+    "i_process_run_mode": InputVariable("numerics", int, choices=[1, -2]),
     "epsvmc": InputVariable("numerics", float, range=(0.0, 1.0)),
     "boundl": InputVariable("numerics", float, array=True),
     "boundu": InputVariable("numerics", float, array=True),
diff --git a/process/core/io/in_dat/base.py b/process/core/io/in_dat/base.py
index 32dc649e66..819875a118 100644
--- a/process/core/io/in_dat/base.py
+++ b/process/core/io/in_dat/base.py
@@ -421,14 +421,14 @@ def get_parameters(data, use_string_values=True):
                             value = data["f_nd_impurity_electrons"].get_value[k]
                             parameters[module][name] = value
 
-                elif item == "ioptimz":
+                elif item == "i_process_run_mode":
                     name = item
-                    ioptimz = {}
-                    iop_val = data["ioptimz"].get_value
+                    i_process_run_mode = {}
+                    iop_val = data["i_process_run_mode"].get_value
                     iop_comment = f"{PROCESSRunMode(iop_val).description}"
-                    ioptimz["value"] = iop_val
-                    ioptimz["comment"] = iop_comment
-                    parameters[module][name] = ioptimz
+                    i_process_run_mode["value"] = iop_val
+                    i_process_run_mode["comment"] = iop_comment
+                    parameters[module][name] = i_process_run_mode
 
                 elif item == "zref":
                     for j in range(len(data["zref"].get_value)):
diff --git a/process/core/io/plot/summary.py b/process/core/io/plot/summary.py
index eb95b14759..b8c300bedf 100644
--- a/process/core/io/plot/summary.py
+++ b/process/core/io/plot/summary.py
@@ -12074,7 +12074,7 @@ def plot_cover_page(
     tagno = mfile.get("tagno", scan=-1)
     branch_name = mfile.get("branch_name", scan=-1)
     fileprefix = mfile.get("fileprefix", scan=-1)
-    optmisation_switch = int(mfile.get("ioptimz", scan=-1))
+    optmisation_switch = int(mfile.get("i_process_run_mode", scan=-1))
     minmax_switch = mfile.get("minmax", scan=-1) or "N/A"
     ifail = mfile.get("ifail", scan=-1)
     nvars = mfile.get("nvar", scan=-1)
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 9bc4baddc3..3de0b2f83f 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -42,7 +42,7 @@ class SolverOutputCondition(IntEnum):
 
 class PROCESSRunMode(IntEnum):
     """Enumeration of the available PROCESS run modes, which determine the behaviour
-    of the code in various places. This is controlled by the `ioptimz` variable
+    of the code in various places. This is controlled by the `i_process_run_mode` variable
     """
 
     EVALUATION = (-2, "Evaluation mode (no optimisation)")
@@ -147,7 +147,7 @@ def description(self):
 class NumericsData:
     """Dataclass holding numerics variables"""
 
-    ioptimz: int = 1
+    i_process_run_mode: int = 1
     """Code operation switch:
     * -2 for evaluation mode (i.e. no optimisation)
     * 1 for optimisation mode (e.g. via VMCON)
diff --git a/process/main.py b/process/main.py
index 2501505685..1bf577bfa1 100644
--- a/process/main.py
+++ b/process/main.py
@@ -446,16 +446,18 @@ def run_scan(self):
             If invalid ioptimiz value selected
         """
         # TODO Move this solver logic up to init?
-        # ioptimz == 1: optimisation
-        if self.data.numerics.ioptimz == PROCESSRunMode.OPTIMISATION:
+        # i_process_run_mode == 1: optimisation
+        if self.data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION:
             pass
-        elif self.data.numerics.ioptimz == PROCESSRunMode.EVALUATION:
+        # i_process_run_mode == -2: evaluation
+        elif self.data.numerics.i_process_run_mode == PROCESSRunMode.EVALUATION:
             # No optimisation:
             # solve equality (consistency) constraints only using fsolve (HYBRD)
             self.solver = "fsolve"
         else:
             raise ValueError(
-                f"Invalid ioptimz value: {self.data.numerics.ioptimz}. Please "
+                f"Invalid i_process_run_mode value: "
+                f"{self.data.numerics.i_process_run_mode}. Please "
                 "select either 1 (optimise) or -2 (no optimisation)."
             )
         self.scan = Scan(self.models, self.solver, self.data)
diff --git a/process/models/physics/l_h_transition.py b/process/models/physics/l_h_transition.py
index c0245279bb..70c12584a8 100644
--- a/process/models/physics/l_h_transition.py
+++ b/process/models/physics/l_h_transition.py
@@ -307,7 +307,7 @@ def output(self) -> None:
             self.outfile,
             f"{PlasmaConfinementTransitionModel(self.data.physics.i_l_h_threshold).full_name}",
         )
-        if (self.data.numerics.ioptimz > 0) and (
+        if (self.data.numerics.i_process_run_mode > 0) and (
             self.data.numerics.active_constraints[14]
         ):
             po.ovarre(
diff --git a/process/models/power.py b/process/models/power.py
index dc3caa32e8..144b6961aa 100644
--- a/process/models/power.py
+++ b/process/models/power.py
@@ -675,7 +675,7 @@ def pfpwr(self, output: bool, pulse_timings: PulseTimings):
             "OP ",
         )
 
-        if (self.data.numerics.ioptimz > 0) and (
+        if (self.data.numerics.i_process_run_mode > 0) and (
             self.data.numerics.active_constraints[65]
         ):
             po.ovarre(
diff --git a/tests/integration/data/large_tokamak_eval.IN.DAT b/tests/integration/data/large_tokamak_eval.IN.DAT
index f988e4f446..87ffdd82f5 100644
--- a/tests/integration/data/large_tokamak_eval.IN.DAT
+++ b/tests/integration/data/large_tokamak_eval.IN.DAT
@@ -1,5 +1,5 @@
 * Evaluation problem: evaluate models consistently by solving equality constraints only
-ioptimz  = -2
+i_process_run_mode  = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
diff --git a/tests/regression/input_files/helias_5b.IN.DAT b/tests/regression/input_files/helias_5b.IN.DAT
index 88ef010ff0..cd71861065 100644
--- a/tests/regression/input_files/helias_5b.IN.DAT
+++ b/tests/regression/input_files/helias_5b.IN.DAT
@@ -150,7 +150,7 @@ f_nd_impurity_electrons(14) = 1.0E-5       *Tungsten
 
 *---------------------Numerics---------------------*
 
-ioptimz  = 1            *Code operation switch (1: Optimisation, VMCON only)
+i_process_run_mode  = 1            *Code operation switch (1: Optimisation, VMCON only)
 maxcal   = 100          *Maximum number of VMCON iterations
 minmax   = 7            *Switch for figure-of-merit (7: Min Capital Cost)
 runtitle = HELIAS-5B
diff --git a/tests/regression/input_files/large_tokamak_eval.IN.DAT b/tests/regression/input_files/large_tokamak_eval.IN.DAT
index 31cc811a25..3a2210a5a6 100644
--- a/tests/regression/input_files/large_tokamak_eval.IN.DAT
+++ b/tests/regression/input_files/large_tokamak_eval.IN.DAT
@@ -1,5 +1,5 @@
 * Evaluation problem: evaluate models consistently by solving equality constraints only
-ioptimz  = -2
+i_process_run_mode  = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
diff --git a/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT b/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
index 53c1f25fc1..bacd7e0d40 100644
--- a/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
+++ b/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
@@ -24,7 +24,7 @@ epsvmc   = 1.0e-8
 * DESCRIPTION:   Error tolerance for VMCON
 * JUSTIFICATION: Same tolerance as used on on previous DEMO
 
-ioptimz  = 1 
+i_process_run_mode  = 1 
 * DESCRIPTION:   Code operation switch (1: VMCON)
 * JUSTIFICATION: Optimised run
 
diff --git a/tests/regression/input_files/spherical_tokamak_eval.IN.DAT b/tests/regression/input_files/spherical_tokamak_eval.IN.DAT
index 2bed0aa45a..dd74bbf4e6 100644
--- a/tests/regression/input_files/spherical_tokamak_eval.IN.DAT
+++ b/tests/regression/input_files/spherical_tokamak_eval.IN.DAT
@@ -1,5 +1,5 @@
 * Evaluation problem: evaluate models consistently by solving equality constraints only
-ioptimz = -2
+i_process_run_mode = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
diff --git a/tests/regression/input_files/st_regression.IN.DAT b/tests/regression/input_files/st_regression.IN.DAT
index c8f51637b6..ea42908d48 100644
--- a/tests/regression/input_files/st_regression.IN.DAT
+++ b/tests/regression/input_files/st_regression.IN.DAT
@@ -47,7 +47,7 @@ epsvmc = 1e-9
 * DESCRIPTION:   HYBRD/VMCON derivative step length
 * JUSTIFICATION: Default step length
 
-ioptimz = 1
+i_process_run_mode = 1
 * DESCRIPTION:   Code operation switch (1: VMCON)
 * JUSTIFICATION: Optimised run
 
diff --git a/tests/regression/input_files/stellarator_helias.IN.DAT b/tests/regression/input_files/stellarator_helias.IN.DAT
index b5d0f1f8bb..187f7139de 100644
--- a/tests/regression/input_files/stellarator_helias.IN.DAT
+++ b/tests/regression/input_files/stellarator_helias.IN.DAT
@@ -224,7 +224,7 @@ f_nd_impurity_electrons(14) = 1.0E-5       *Tungsten
 
 *---------------------Numerics---------------------*
 
-ioptimz  = 1            *Code operation switch (1: Optimisation, VMCON only)
+i_process_run_mode  = 1            *Code operation switch (1: Optimisation, VMCON only)
 maxcal   = 100          *Maximum number of VMCON iterations
 minmax   = 6            *Switch for figure-of-merit (7: Min Capital Cost)
 epsfcn   = 0.01         *Default for this parameter is 1e-3 however this specific IN.DAT and starting point benefit from a larger step length
diff --git a/tests/regression/test_process_input_files.py b/tests/regression/test_process_input_files.py
index 00f574f825..342477da26 100644
--- a/tests/regression/test_process_input_files.py
+++ b/tests/regression/test_process_input_files.py
@@ -127,7 +127,7 @@ def compare(
 
         assert (
             ifail == SolverOutputCondition.CONVERGED
-            or mfile.data["ioptimz"].get_scan(-1) == -2
+            or mfile.data["i_process_run_mode"].get_scan(-1) == -2
         ), (
             f"\033[0;36m ifail of {ifail} indicates PROCESS did not solve "
             "successfully\033[0m"
diff --git a/tests/unit/core/test_input.py b/tests/unit/core/test_input.py
index 48fcb4984a..6175e19481 100644
--- a/tests/unit/core/test_input.py
+++ b/tests/unit/core/test_input.py
@@ -107,14 +107,14 @@ def test_parse_input(tmp_path, data_structure_obj):
     init.init_process(data_structure_obj)
 
     assert data_structure_obj.globals.runtitle == "my run title"
-    assert data_structure_obj.numerics.ioptimz == PROCESSRunMode.EVALUATION
+    assert data_structure_obj.numerics.i_process_run_mode == PROCESSRunMode.EVALUATION
     assert pytest.approx(data_structure_obj.numerics.epsvmc) == 0.6
     assert pytest.approx(data_structure_obj.numerics.boundl[0]) == 0.5
 
 
 def test_input_choices(tmp_path, data_structure_obj):
     data_structure_obj.globals.fileprefix = _create_input_file(
-        tmp_path, ("ioptimz = -1")
+        tmp_path, ("i_process_run_mode = -1")
     )
 
     with pytest.raises(ProcessValidationError):
@@ -156,7 +156,7 @@ def test_input_not_array_when_is(tmp_path, data_structure_obj):
 
 def test_input_float_when_int(tmp_path, data_structure_obj):
     data_structure_obj.globals.fileprefix = _create_input_file(
-        tmp_path, ("ioptimz = 0.5")
+        tmp_path, ("i_process_run_mode = 0.5")
     )
 
     with pytest.raises(ProcessValidationError):
diff --git a/tests/unit/models/test_power.py b/tests/unit/models/test_power.py
index 263b726f86..fa28f1ea51 100644
--- a/tests/unit/models/test_power.py
+++ b/tests/unit/models/test_power.py
@@ -166,7 +166,7 @@ class PfpwrParam(NamedTuple):
 
     active_constraints: Any = None
 
-    ioptimz: Any = None
+    i_process_run_mode: Any = None
 
     pulse_timings: PulseTimings = None
 
@@ -784,7 +784,7 @@ class PfpwrParam(NamedTuple):
                 False,
                 False,
             ),
-            ioptimz=1,
+            i_process_run_mode=1,
             pulse_timings=PulseTimings(
                 t_plant_pulse_coil_precharge=500,
                 t_plant_pulse_plasma_current_ramp_up=177.21306969367816,
@@ -1405,7 +1405,7 @@ class PfpwrParam(NamedTuple):
                 False,
                 False,
             ),
-            ioptimz=1,
+            i_process_run_mode=1,
             pulse_timings=PulseTimings(
                 t_plant_pulse_coil_precharge=500,
                 t_plant_pulse_plasma_current_ramp_up=177.21306969367816,
@@ -1485,7 +1485,9 @@ def test_pfpwr(pfpwrparam, monkeypatch, power):
         power.data.numerics, "active_constraints", pfpwrparam.active_constraints
     )
 
-    monkeypatch.setattr(power.data.numerics, "ioptimz", pfpwrparam.ioptimz)
+    monkeypatch.setattr(
+        power.data.numerics, "i_process_run_mode", pfpwrparam.i_process_run_mode
+    )
 
     monkeypatch.setattr(
         power.data.times,

From 42c036e5f61d5db1d1f5fa3e25580944dfbe77be Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:04:23 +0100
Subject: [PATCH 04/13] Rename `minmax` to `i_figure_merit` for consistency
 with style guide

---
 documentation/source/development/add-vars.md       |  4 ++--
 documentation/source/io/input-guide.md             |  6 +++---
 documentation/source/solver/solver-guide.md        |  6 +++---
 .../large_tokamak_varied_min_net_electric_IN.DAT   |  2 +-
 examples/data/large_tokamak_varyrun_IN.DAT         |  2 +-
 examples/data/mfile_to_csv_vars.json               |  2 +-
 process/core/caller.py                             |  2 +-
 process/core/init.py                               | 11 +++++++----
 process/core/input.py                              |  2 +-
 process/core/io/plot/solutions.py                  |  7 ++++---
 process/core/io/plot/summary.py                    |  8 ++++----
 process/core/solver/objectives.py                  | 14 ++++++++------
 process/data_structure/numerics.py                 |  8 +++-----
 tests/regression/input_files/IFE.IN.DAT            |  2 +-
 tests/regression/input_files/helias_5b.IN.DAT      |  2 +-
 .../input_files/large_tokamak_nof.IN.DAT           |  2 +-
 .../input_files/low_aspect_ratio_DEMO.IN.DAT       |  2 +-
 tests/regression/input_files/st_regression.IN.DAT  |  2 +-
 .../input_files/stellarator_helias.IN.DAT          |  2 +-
 19 files changed, 45 insertions(+), 41 deletions(-)

diff --git a/documentation/source/development/add-vars.md b/documentation/source/development/add-vars.md
index 703a648e52..e88cb7da03 100644
--- a/documentation/source/development/add-vars.md
+++ b/documentation/source/development/add-vars.md
@@ -128,9 +128,9 @@ Note that you will want to scale the `objective_metric` such that it is of the o
 
 The figure of merit can be selected in the `IN.DAT`:
 ```
-minmax = 20
+i_figure_merit = 20
 ```
-Remember, setting `minmax = -20` would minimise instead of maximise our new variable.
+Remember, setting `i_figure_merit = -20` would minimise instead of maximise our new variable.
 
 -----------------
 
diff --git a/documentation/source/io/input-guide.md b/documentation/source/io/input-guide.md
index 388f36a1b0..979dffe8be 100644
--- a/documentation/source/io/input-guide.md
+++ b/documentation/source/io/input-guide.md
@@ -117,13 +117,13 @@ i_process_run_mode  = 1 * for optimisation VMCON only
 The user can select the figure of merit to be used:
 
 ```
-minmax   = 1 * Switch for figure-of-merit (see `FiguresOfMerit` for descriptions)
+i_figure_merit   = 1 * Switch for figure-of-merit (see `FiguresOfMerit` for descriptions)
 ```
 
 !!! Info "Figures of Merit"
-    The full list of valid `minmax` values is documented in the API reference for [`process.data_structure.numerics.FiguresOfMerit`](../../source/reference/process/data_structure/numerics/#process.data_structure.numerics.FiguresOfMerit).
+    The full list of valid `i_figure_merit` values is documented in the API reference for [`process.data_structure.numerics.FiguresOfMerit`](../../source/reference/process/data_structure/numerics/#process.data_structure.numerics.FiguresOfMerit).
 
-In this case the user is choosing option `1`, which is major radius. For `minmax`
+In this case the user is choosing option `1`, which is major radius. For `i_figure_merit`
 
 * a **positive** value means **minimise** the figure of merit
 * a **negative** value means **maximise** the figure of merit
diff --git a/documentation/source/solver/solver-guide.md b/documentation/source/solver/solver-guide.md
index 9173f205f8..9bd1d9a3f9 100644
--- a/documentation/source/solver/solver-guide.md
+++ b/documentation/source/solver/solver-guide.md
@@ -96,9 +96,9 @@ known as the figure of merit.
 Several possible figures of merit are available, all of which are in the 
 source file `evaluators.f90`. 
 
-Switch `minmax` is used to control which figure of merit is to be used. If the 
-figure of merit is to be minimised, `minmax` should be **positive**, and if a 
-maximised figure of merit is desired, `minmax` should be **negative**.
+Switch `i_figure_merit` is used to control which figure of merit is to be used. If the 
+figure of merit is to be minimised, `i_figure_merit` should be **positive**, and if a 
+maximised figure of merit is desired, `i_figure_merit` should be **negative**.
 
 ## Convergence
 
diff --git a/examples/data/large_tokamak_varied_min_net_electric_IN.DAT b/examples/data/large_tokamak_varied_min_net_electric_IN.DAT
index 1242997d88..4bd231f456 100644
--- a/examples/data/large_tokamak_varied_min_net_electric_IN.DAT
+++ b/examples/data/large_tokamak_varied_min_net_electric_IN.DAT
@@ -12,7 +12,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/examples/data/large_tokamak_varyrun_IN.DAT b/examples/data/large_tokamak_varyrun_IN.DAT
index 1e93cb8cd7..6e327c2f33 100644
--- a/examples/data/large_tokamak_varyrun_IN.DAT
+++ b/examples/data/large_tokamak_varyrun_IN.DAT
@@ -12,7 +12,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/examples/data/mfile_to_csv_vars.json b/examples/data/mfile_to_csv_vars.json
index 4a7bf41304..6192ea99a8 100644
--- a/examples/data/mfile_to_csv_vars.json
+++ b/examples/data/mfile_to_csv_vars.json
@@ -1,6 +1,6 @@
 {
   "vars": [
-    "minmax",
+    "i_figure_merit",
     "p_hcd_injected_max",
     "p_plant_electric_net_required_mw",
     "ripple_b_tf_plasma_edge_max",
diff --git a/process/core/caller.py b/process/core/caller.py
index 1634777e53..dabc5054d8 100644
--- a/process/core/caller.py
+++ b/process/core/caller.py
@@ -100,7 +100,7 @@ def call_models(self, xc: np.ndarray, m: int) -> tuple[float, np.ndarray]:
         for _ in range(10):
             self._call_models_once(xc)
             # Evaluate objective function and constraints
-            objf = objective_function(self.data.numerics.minmax, self.data)
+            objf = objective_function(self.data.numerics.i_figure_merit, self.data)
             conf, _, _, _, _ = constraints.constraint_eqns(m, -1, self.data)
 
             if objf_prev is None and conf_prev is None:
diff --git a/process/core/init.py b/process/core/init.py
index 9c22d0b3bc..968310ec5a 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -191,17 +191,17 @@ def run_summary(data: DataStructure):
                 f"Max iterations : {data.globals.maxcal}",
             )
 
-            if data.numerics.minmax > 0:
+            if data.numerics.i_figure_merit > 0:
                 minmax_string = "  -- minimise "
                 minmax_sign = "+"
             else:
                 minmax_string = "  -- maximise "
                 minmax_sign = "-"
 
-            fom_string = FiguresOfMerit(abs(data.numerics.minmax)).description
+            fom_string = FiguresOfMerit(abs(data.numerics.i_figure_merit)).description
             process_output.ocmmnt(
                 outfile,
-                f"Figure of merit : {minmax_sign}{abs(data.numerics.minmax)}"
+                f"Figure of merit : {minmax_sign}{abs(data.numerics.i_figure_merit)}"
                 f"{minmax_string}{fom_string}",
             )
             process_output.ocmmnt(
@@ -235,7 +235,10 @@ def run_summary(data: DataStructure):
     # If optimising, write figure of merit switch
     if data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION:
         process_output.ovarre(
-            mfile, "Figure of merit switch", "(minmax)", data.numerics.minmax
+            mfile,
+            "Figure of merit switch",
+            "(i_figure_merit)",
+            data.numerics.i_figure_merit,
         )
 
 
diff --git a/process/core/input.py b/process/core/input.py
index 0fba32c17d..ec7142c8b3 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -152,7 +152,7 @@ def bounds(self) -> tuple[NumberType | None, NumberType | None]:
     "boundu": InputVariable("numerics", float, array=True),
     "epsfcn": InputVariable("numerics", float, range=(0.0, 1.0)),
     "maxcal": InputVariable("globals", int, range=(0, 10000)),
-    "minmax": InputVariable("numerics", int),
+    "i_figure_merit": InputVariable("numerics", int),
     "neqns": InputVariable(
         "numerics", int, range=(0, ConstraintManager.num_constraints())
     ),
diff --git a/process/core/io/plot/solutions.py b/process/core/io/plot/solutions.py
index 34811f8f03..18260b96b2 100644
--- a/process/core/io/plot/solutions.py
+++ b/process/core/io/plot/solutions.py
@@ -141,7 +141,7 @@ def plot_mfile_solutions(
     filtered_results_df = _filter_vars_of_interest(
         results_df,
         opt_param_value_pattern=opt_param_value_pattern,
-        extra_var_names=["minmax"],
+        extra_var_names=["i_figure_merit"],
     )
 
     if normalising_tag is not None:
@@ -456,7 +456,7 @@ def _plot_solutions(
     # Acquire objective function name(s), then check only one type is being plotted
     # The objective function is found by first checking the NORM_OBJF_NAME column.
     # If this entry does not exist for any of the MFiles (ie they are old),
-    # then the code 'falls back' to the the minmax output. Which holds the same
+    # then the code 'falls back' to the the i_figure_merit output. Which holds the same
     # information, but is less descriptive.
     if (
         NORM_OBJF_NAME in norm_objf_df.columns
@@ -465,7 +465,8 @@ def _plot_solutions(
         objf_list = norm_objf_df[NORM_OBJF_NAME].unique()
     else:
         objf_list = {
-            FiguresOfMerit(abs(int(minmax))).description for minmax in diffs_df["minmax"]
+            FiguresOfMerit(abs(int(i_figure_merit))).description
+            for i_figure_merit in diffs_df["i_figure_merit"]
         }
 
     if len(objf_list) != 1:
diff --git a/process/core/io/plot/summary.py b/process/core/io/plot/summary.py
index b8c300bedf..8a6035d2de 100644
--- a/process/core/io/plot/summary.py
+++ b/process/core/io/plot/summary.py
@@ -8234,9 +8234,9 @@ def plot_header(axis: plt.Axes, mfile: MFile, scan: int):
         (f"!{mfile.get('username', scan=-1)}", "User:", ""),
         (
             ("!Evaluation", "Run type", "")
-            if isinstance(mfile.data["minmax"], MFileErrorClass)
+            if isinstance(mfile.data["i_figure_merit"], MFileErrorClass)
             else (
-                f"!{FiguresOfMerit(abs(int(mfile.get('minmax', scan=-1)))).description}",
+                f"!{FiguresOfMerit(abs(int(mfile.get('i_figure_merit', scan=-1)))).description}",
                 "Optimising:",
                 "",
             )
@@ -12075,7 +12075,7 @@ def plot_cover_page(
     branch_name = mfile.get("branch_name", scan=-1)
     fileprefix = mfile.get("fileprefix", scan=-1)
     optmisation_switch = int(mfile.get("i_process_run_mode", scan=-1))
-    minmax_switch = mfile.get("minmax", scan=-1) or "N/A"
+    minmax_switch = mfile.get("i_figure_merit", scan=-1) or "N/A"
     ifail = mfile.get("ifail", scan=-1)
     nvars = mfile.get("nvar", scan=-1)
     # Objective_function_name
@@ -12157,7 +12157,7 @@ def plot_cover_page(
     settings_info = (
         f"• Optimisation Switch: {int(optmisation_switch)}\n"
         f"     {PROCESSRunMode(int(optmisation_switch)).description}\n"
-        f"• Figure of Merit Switch (minmax): {minmax_switch}\n"
+        f"• Figure of Merit Switch (i_figure_merit): {minmax_switch}\n"
         f"     {objective_text}\n"
         f"• Fail Status (ifail): {int(ifail)}\n"
         f"• Number of Iteration Variables: {int(nvars)}\n"
diff --git a/process/core/solver/objectives.py b/process/core/solver/objectives.py
index b0a46a7d79..e8b369d6e3 100644
--- a/process/core/solver/objectives.py
+++ b/process/core/solver/objectives.py
@@ -8,12 +8,12 @@
 from process.models.availability import AvailabilityModel
 
 
-def objective_function(minmax: int, data: DataStructure) -> float:
+def objective_function(i_figure_merit: int, data: DataStructure) -> float:
     """Calculate the specified objective function
 
     Parameters
     ----------
-    minmax : int
+    i_figure_merit : int
         the ID and sign of the figure of merit to evaluate.
         A negative value indicates maximisation.
         A positive value indicates minimisation.
@@ -43,13 +43,15 @@ def objective_function(minmax: int, data: DataStructure) -> float:
         If minmax=15 not used with i_plant_availability=1
     """
     try:
-        figure_of_merit = FiguresOfMerit(abs(minmax))
+        figure_of_merit = FiguresOfMerit(abs(i_figure_merit))
     except ValueError as err:
-        raise ProcessValueError(f"Invalid minmax value: {minmax}") from err
+        raise ProcessValueError(
+            f"Invalid i_figure_merit value: {i_figure_merit}"
+        ) from err
 
     # -1 = maximise
     # +1 = minimise
-    objective_sign = np.sign(minmax)
+    objective_sign = np.sign(i_figure_merit)
 
     if figure_of_merit == FiguresOfMerit.MAJOR_RADIUS:
         objective_metric = 0.2 * data.physics.rmajor
@@ -83,7 +85,7 @@ def objective_function(minmax: int, data: DataStructure) -> float:
             == AvailabilityModel.USER_INPUT
         ):
             raise ProcessValueError(
-                "minmax=15 requires `f_t_plant_available` to be calculated, not user "
+                "i_figure_merit=15 requires `f_t_plant_available` to be calculated, not user "
                 "input"
             )
         objective_metric = data.costs.f_t_plant_available
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 3de0b2f83f..5e8b641431 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -147,13 +147,11 @@ def description(self):
 class NumericsData:
     """Dataclass holding numerics variables"""
 
-    i_process_run_mode: int = 1
-    """Code operation switch:
-    * -2 for evaluation mode (i.e. no optimisation)
-    * 1 for optimisation mode (e.g. via VMCON)
+    i_process_run_mode: int | PROCESSRunMode = 1
+    """PROCESS run mode (see `PROCESSRunMode` for descriptions)
     """
 
-    minmax: int = 7
+    i_figure_merit: int | FiguresOfMerit = 7
     """
     Switch for figure-of-merit (see `FiguresOfMerit` for descriptions)
     negative => maximise, positive => minimise
diff --git a/tests/regression/input_files/IFE.IN.DAT b/tests/regression/input_files/IFE.IN.DAT
index 3531124839..e4e602dd55 100644
--- a/tests/regression/input_files/IFE.IN.DAT
+++ b/tests/regression/input_files/IFE.IN.DAT
@@ -24,7 +24,7 @@ p_plant_electric_net_required_mw  = 1000.0     *Required net electric power (MW)
 
 *---------------Numerics Variables-----------------*
 IOPTIMZ   = 1         *Code operation switch (1: for optimisation VMCON only)
-minmax    = 18        *Null FoM, find feasible
+i_figure_merit    = 18        *Null FoM, find feasible
 maxcal    = 100       *Maximum number of solver iterations
 
 
diff --git a/tests/regression/input_files/helias_5b.IN.DAT b/tests/regression/input_files/helias_5b.IN.DAT
index cd71861065..757479601d 100644
--- a/tests/regression/input_files/helias_5b.IN.DAT
+++ b/tests/regression/input_files/helias_5b.IN.DAT
@@ -152,7 +152,7 @@ f_nd_impurity_electrons(14) = 1.0E-5       *Tungsten
 
 i_process_run_mode  = 1            *Code operation switch (1: Optimisation, VMCON only)
 maxcal   = 100          *Maximum number of VMCON iterations
-minmax   = 7            *Switch for figure-of-merit (7: Min Capital Cost)
+i_figure_merit   = 7            *Switch for figure-of-merit (7: Min Capital Cost)
 runtitle = HELIAS-5B
 
 *-----------------Tfcoil Variables-----------------*
diff --git a/tests/regression/input_files/large_tokamak_nof.IN.DAT b/tests/regression/input_files/large_tokamak_nof.IN.DAT
index bf16597a38..b2f325a631 100644
--- a/tests/regression/input_files/large_tokamak_nof.IN.DAT
+++ b/tests/regression/input_files/large_tokamak_nof.IN.DAT
@@ -12,7 +12,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT b/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
index bacd7e0d40..a9b34bd7f7 100644
--- a/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
+++ b/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
@@ -28,7 +28,7 @@ i_process_run_mode  = 1
 * DESCRIPTION:   Code operation switch (1: VMCON)
 * JUSTIFICATION: Optimised run
 
-minmax   = -14 * Switch for figure-of-merit (see lablmm for descriptions)
+i_figure_merit   = -14 * Switch for figure-of-merit (see lablmm for descriptions)
 * 14: pulse length
 * DESCRIPTION:   Switch for Figure-of-Merit (1: Minimise major radius)
 * JUSTIFICATION: Aim to minimise major radius
diff --git a/tests/regression/input_files/st_regression.IN.DAT b/tests/regression/input_files/st_regression.IN.DAT
index ea42908d48..5e52ccad64 100644
--- a/tests/regression/input_files/st_regression.IN.DAT
+++ b/tests/regression/input_files/st_regression.IN.DAT
@@ -51,7 +51,7 @@ i_process_run_mode = 1
 * DESCRIPTION:   Code operation switch (1: VMCON)
 * JUSTIFICATION: Optimised run
 
-minmax = -5
+i_figure_merit = -5
 * DESCRIPTION:   Switch for Figure-of-Merit 
 * JUSTIFICATION: Selected optimisation
 
diff --git a/tests/regression/input_files/stellarator_helias.IN.DAT b/tests/regression/input_files/stellarator_helias.IN.DAT
index 187f7139de..3fcb03beb5 100644
--- a/tests/regression/input_files/stellarator_helias.IN.DAT
+++ b/tests/regression/input_files/stellarator_helias.IN.DAT
@@ -226,7 +226,7 @@ f_nd_impurity_electrons(14) = 1.0E-5       *Tungsten
 
 i_process_run_mode  = 1            *Code operation switch (1: Optimisation, VMCON only)
 maxcal   = 100          *Maximum number of VMCON iterations
-minmax   = 6            *Switch for figure-of-merit (7: Min Capital Cost)
+i_figure_merit   = 6            *Switch for figure-of-merit (7: Min Capital Cost)
 epsfcn   = 0.01         *Default for this parameter is 1e-3 however this specific IN.DAT and starting point benefit from a larger step length
 runtitle = SQuID
 

From e8286632e64a15d4542acb2f65f44c0862a7b3ca Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:09:59 +0100
Subject: [PATCH 05/13] Rename `neqns` to `n_equality_constraints` for
 consistency with style guide

---
 documentation/source/solver/solver-guide.md   |  6 +-
 examples/data/large_tokamak_eval_IN.DAT       |  2 +-
 ...rge_tokamak_varied_min_net_electric_IN.DAT |  2 +-
 examples/data/large_tokamak_varyrun_IN.DAT    |  2 +-
 process/core/init.py                          | 86 +++++++++++++------
 process/core/input.py                         |  2 +-
 process/core/io/in_dat/base.py                |  5 +-
 process/core/io/vary_run/tools.py             |  8 +-
 process/data_structure/numerics.py            |  4 +-
 .../data/large_tokamak_eval.IN.DAT            |  2 +-
 tests/integration/test_vmcon.py               | 30 +++----
 tests/regression/input_files/IFE.IN.DAT       |  2 +-
 tests/regression/input_files/helias_5b.IN.DAT |  2 +-
 .../input_files/large_tokamak_eval.IN.DAT     |  2 +-
 .../input_files/large_tokamak_nof.IN.DAT      |  4 +-
 .../input_files/low_aspect_ratio_DEMO.IN.DAT  |  2 +-
 .../input_files/spherical_tokamak_eval.IN.DAT |  2 +-
 .../input_files/st_regression.IN.DAT          |  4 +-
 .../input_files/stellarator_helias.IN.DAT     |  2 +-
 19 files changed, 104 insertions(+), 65 deletions(-)

diff --git a/documentation/source/solver/solver-guide.md b/documentation/source/solver/solver-guide.md
index 9bd1d9a3f9..be891cce1a 100644
--- a/documentation/source/solver/solver-guide.md
+++ b/documentation/source/solver/solver-guide.md
@@ -15,7 +15,7 @@ A PROCESS input file will, for example, define which constraint equations are be
 
 ```
 ...
-neqns = 3
+n_equality_constraints = 3
 
 * Equalities
 icc = 1 * Beta
@@ -33,7 +33,7 @@ icc = 15 * LH power threshold limit
 Here each `icc=n` statement tells PROCESS to activate a constraint with the name `n`. A list of the constraints and 
 their corresponding names can be found [here](../../source/reference/process/data_structure/numerics/#process.data_structure.numerics.lablcc).
 
-The `neqns = 3` statement is telling PROCESS to treat the first `3` equations as equality constraints, and the rest as inequality constraints. Therefore, it is imperative that all equality constraints are stated before any inequality constraints.
+The `n_equality_constraints = 3` statement is telling PROCESS to treat the first `3` equations as equality constraints, and the rest as inequality constraints. Therefore, it is imperative that all equality constraints are stated before any inequality constraints.
 
 
 In both types of equations, an optimiser/solver uses the normalised residuals $c_i$ of the constraints (and sometimes its gradient, depending on the solver/optimiser) to guide the solution towards one that satisfies all of the constraints.
@@ -141,7 +141,7 @@ i_process_run_mode  = -2 * evaluation mode
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
-neqns = 2
+n_equality_constraints = 2
 
 * Equalities
 icc = 1 * Beta
diff --git a/examples/data/large_tokamak_eval_IN.DAT b/examples/data/large_tokamak_eval_IN.DAT
index 1b81c32a2d..f92b56ea19 100644
--- a/examples/data/large_tokamak_eval_IN.DAT
+++ b/examples/data/large_tokamak_eval_IN.DAT
@@ -3,7 +3,7 @@ i_process_run_mode  = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
-neqns = 2
+n_equality_constraints = 2
 
 * Equalities
 icc = 1 * Beta
diff --git a/examples/data/large_tokamak_varied_min_net_electric_IN.DAT b/examples/data/large_tokamak_varied_min_net_electric_IN.DAT
index 4bd231f456..0e6abd3b44 100644
--- a/examples/data/large_tokamak_varied_min_net_electric_IN.DAT
+++ b/examples/data/large_tokamak_varied_min_net_electric_IN.DAT
@@ -17,7 +17,7 @@ i_figure_merit = 1
 * Error tolerance for VMCON
 epsvmc = 1e-7
 
-neqns = 3
+n_equality_constraints = 3
 
 * Constraint Equations - Consistency Equations *
 ************************************************
diff --git a/examples/data/large_tokamak_varyrun_IN.DAT b/examples/data/large_tokamak_varyrun_IN.DAT
index 6e327c2f33..9f0c33f3eb 100644
--- a/examples/data/large_tokamak_varyrun_IN.DAT
+++ b/examples/data/large_tokamak_varyrun_IN.DAT
@@ -17,7 +17,7 @@ i_figure_merit = 1
 * Error tolerance for VMCON
 epsvmc = 1e-7
 
-neqns = 3
+n_equality_constraints = 3
 
 * Constraint Equations - Consistency Equations *
 ************************************************
diff --git a/process/core/init.py b/process/core/init.py
index 968310ec5a..e72991befe 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -174,14 +174,17 @@ def run_summary(data: DataStructure):
         process_output.ostars(outfile, 110)
         process_output.oblnkl(outfile)
 
-        process_output.ocmmnt(outfile, f"Equality constraints : {data.numerics.neqns}")
+        process_output.ocmmnt(
+            outfile, f"Equality constraints : {data.numerics.n_equality_constraints}"
+        )
         process_output.ocmmnt(
             outfile,
             f"Inequality constraints : {data.numerics.nineqns}",
         )
         process_output.ocmmnt(
             outfile,
-            f"Total constraints : {data.numerics.nineqns + data.numerics.neqns}",
+            f"Total constraints : "
+            f"{data.numerics.nineqns + data.numerics.n_equality_constraints}",
         )
         process_output.ocmmnt(outfile, f"Iteration variables : {data.numerics.nvar}")
         # If optimising, write objective function and convergence parameter
@@ -256,11 +259,11 @@ def check_process(inputs, data):  # noqa: ARG001
         See individual ProcessValidationError instances for more details.
     """
     # Check that there are sufficient iteration variables
-    if data.numerics.nvar < data.numerics.neqns:
+    if data.numerics.nvar < data.numerics.n_equality_constraints:
         raise ProcessValidationError(
             "Insufficient iteration variables to solve the problem! NVAR < NEQNS",
             nvar=data.numerics.nvar,
-            neqns=data.numerics.neqns,
+            n_equality_constraints=data.numerics.n_equality_constraints,
         )
 
     # Check that sufficient elements of ixc and icc have been specified
@@ -301,18 +304,23 @@ def check_process(inputs, data):  # noqa: ARG001
             "constraint 77 (maximum TF current per turn) simultaneously."
         )
 
-    if (data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 0).any():
+    if (
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 0
+    ).any():
         raise ProcessValidationError(
             "The number of constraints specified is smaller than the number stated"
-            " in neqns+nineqns",
-            neqns=data.numerics.neqns,
+            " in n_equality_constraints+nineqns",
+            n_equality_constraints=data.numerics.n_equality_constraints,
             nineqns=data.numerics.nineqns,
         )
 
     # Deprecate constraints
     for depcrecated_constraint in [3, 4, 10, 74, 42]:
         if (
-            data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns]
+            data.numerics.icc[
+                : data.numerics.n_equality_constraints + data.numerics.nineqns
+            ]
             == depcrecated_constraint
         ).any():
             raise ProcessValidationError(
@@ -321,7 +329,8 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # MDK Report error if constraint 63 is used with old vacuum model
     if (
-        data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 63
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 63
     ).any() and data.vacuum.i_vacuum_pumping != "simple":
         raise ProcessValidationError(
             "Constraint 63 is requested without the correct vacuum model (simple)"
@@ -496,7 +505,10 @@ def check_process(inputs, data):  # noqa: ARG001
         if (
             data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION
             and not (
-                data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 81
+                data.numerics.icc[
+                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                ]
+                == 81
             ).any()
         ):
             if (data.numerics.ixc[: data.numerics.nvar] == 145).any():
@@ -517,9 +529,11 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use Psep/R and PsepB/qAR limits at the same time
     if (
-        data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 68
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 68
     ).any() and (
-        data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 56
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 56
     ).any():
         raise ProcessValidationError(
             "Cannot use Psep/R and PsepB/qAR constraint equations at the same time"
@@ -536,7 +550,10 @@ def check_process(inputs, data):  # noqa: ARG001
             f_nd_plasma_separatrix_greenwald=data.physics.f_nd_plasma_separatrix_greenwald,
         )
 
-    if (data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 78).any():
+    if (
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 78
+    ).any():
         # If Reinke criterion is used temp_plasma_separatrix_kev is calculated and
         # cannot be an iteration variable
         if (data.numerics.ixc[: data.numerics.nvar] == 119).any():
@@ -549,7 +566,10 @@ def check_process(inputs, data):  # noqa: ARG001
         # using Martin scaling for consistency
         if (data.physics.i_l_h_threshold != 6) or (
             not (
-                data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 15
+                data.numerics.icc[
+                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                ]
+                == 15
             ).any()
             and data.physics.i_plasma_pedestal
         ):
@@ -687,7 +707,10 @@ def check_process(inputs, data):  # noqa: ARG001
         if (
             data.tfcoil.i_tf_sup == TFConductorModel.HELIUM_COOLED_ALUMINIUM
             and (
-                data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 85
+                data.numerics.icc[
+                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                ]
+                == 85
             ).any()
             and data.physics.itart == 1
         ):
@@ -760,7 +783,10 @@ def check_process(inputs, data):  # noqa: ARG001
 
         # Constraint 10 is dedicated to ST designs with demountable joints
         if (
-            data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 10
+            data.numerics.icc[
+                : data.numerics.n_equality_constraints + data.numerics.nineqns
+            ]
+            == 10
         ).any():
             raise ProcessValidationError(
                 "Constraint equation 10 (CP lifetime) to used with ST desing (itart=1)"
@@ -797,10 +823,16 @@ def check_process(inputs, data):  # noqa: ARG001
         )  # dr_bore + dr_cs_tf_gap + dr_cs = 0
         and (
             (
-                data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 31
+                data.numerics.icc[
+                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                ]
+                == 31
             ).any()
             or (
-                data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 32
+                data.numerics.icc[
+                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                ]
+                == 32
             ).any()
         )  # Stress constraints (31 or 32) is used
         and (
@@ -1172,7 +1204,8 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use temperature margin constraint with REBCO TF coils
     if (
-        data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 36
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 36
     ).any() and (
         SuperconductorModel(data.tfcoil.i_tf_sc_mat).sc_type
         == SuperconductorMaterial.REBCO
@@ -1183,7 +1216,8 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use temperature margin constraint with REBCO CS coils
     if (
-        data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 60
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 60
     ).any() and data.pf_coil.i_cs_superconductor == 8:
         raise ProcessValidationError(
             "turn off CS temperature margin constraint icc = 60 when using REBCO"
@@ -1195,7 +1229,8 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use TF coil strain limit if i_str_wp is off:
     if (
-        data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns] == 88
+        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        == 88
     ).any() and data.tfcoil.i_str_wp == 0:
         raise ProcessValidationError("Can't use constraint 88 if i_strain_tf == 0")
 
@@ -1208,11 +1243,12 @@ def set_active_constraints(data: DataStructure):
             data.numerics.active_constraints[data.numerics.icc[i] - 1] = True
             num_constraints += 1
 
-    if data.numerics.neqns < 0:
-        # The value of neqns has not been set in the input file.  Default = 0.
-        data.numerics.neqns = num_constraints - data.numerics.nineqns
+    if data.numerics.n_equality_constraints < 0:
+        # The value of n_equality_constraints has not been set in the input file.
+        # Default = 0.
+        data.numerics.n_equality_constraints = num_constraints - data.numerics.nineqns
     else:
-        data.numerics.nineqns = num_constraints - data.numerics.neqns
+        data.numerics.nineqns = num_constraints - data.numerics.n_equality_constraints
 
 
 def set_device_type(data: DataStructure):
diff --git a/process/core/input.py b/process/core/input.py
index ec7142c8b3..d836de9312 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -153,7 +153,7 @@ def bounds(self) -> tuple[NumberType | None, NumberType | None]:
     "epsfcn": InputVariable("numerics", float, range=(0.0, 1.0)),
     "maxcal": InputVariable("globals", int, range=(0, 10000)),
     "i_figure_merit": InputVariable("numerics", int),
-    "neqns": InputVariable(
+    "n_equality_constraints": InputVariable(
         "numerics", int, range=(0, ConstraintManager.num_constraints())
     ),
     "nineqns": InputVariable(
diff --git a/process/core/io/in_dat/base.py b/process/core/io/in_dat/base.py
index 819875a118..c6cc8f0353 100644
--- a/process/core/io/in_dat/base.py
+++ b/process/core/io/in_dat/base.py
@@ -385,7 +385,8 @@ def get_parameters(data, use_string_values=True):
     # dict of all module-level variables in source, grouped by module
     parameters = {}
     # dict of all parameters set in input file, grouped by module
-    # Include neqns to allow eq and ineq constraints to be defined in produced IN.DAT
+    # Include n_equality_constraints to allow eq and ineq constraints to be defined in
+    # produced IN.DAT
     exclusions = ["nvar", "icc", "ixc"]
     # Parameters to exclude
 
@@ -1269,7 +1270,7 @@ def process_constraint_equation(self, line):
                     # Duplicate constraint equation number
                     self.add_duplicate_variable(f"icc = {item}")
             # Don't sort the constraints! Preserves what's eq, what's ineq;
-            # first neqns are eqs, rest are ineqs
+            # first n_equality_constraints are eqs, rest are ineqs
             # self.data["icc"].value.sort()
 
     def process_iteration_variables(self, line):
diff --git a/process/core/io/vary_run/tools.py b/process/core/io/vary_run/tools.py
index 8793ca5d34..396b617c17 100644
--- a/process/core/io/vary_run/tools.py
+++ b/process/core/io/vary_run/tools.py
@@ -297,7 +297,7 @@ def vary_iteration_variables(itervars, lbs, ubs, config: RunProcessConfig):
     return new_values
 
 
-def get_solution_from_mfile(neqns, nvars, wdir=".", mfile="MFILE.DAT"):
+def get_solution_from_mfile(n_equality_constraints, nvars, wdir=".", mfile="MFILE.DAT"):
     """Returns
     ifail - error_value of VMCON/PROCESS
     the objective functions
@@ -319,10 +319,12 @@ def get_solution_from_mfile(neqns, nvars, wdir=".", mfile="MFILE.DAT"):
     constraints = m_file.get("sqsumsq")
 
     table_sol = [m_file.get(f"itvar{var_no + 1:03}") for var_no in range(nvars)]
-    table_res = [m_file.get(f"normres{con_no + 1:03}") for con_no in range(neqns)]
+    table_res = [
+        m_file.get(f"normres{con_no + 1:03}") for con_no in range(n_equality_constraints)
+    ]
 
     if ifail != SolverOutputCondition.CONVERGED:
-        return ifail, "0", "0", ["0"] * nvars, ["0"] * neqns
+        return ifail, "0", "0", ["0"] * nvars, ["0"] * n_equality_constraints
 
     return ifail, objective_function, constraints, table_sol, table_res
 
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 5e8b641431..9c6a382d34 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -158,12 +158,12 @@ class NumericsData:
     """
 
     n_constraints: int = 0
-    """Total number of constraints (neqns + nineqns)"""
+    """Total number of constraints (n_equality_constraints + nineqns)"""
 
     ncalls: int = 0
     """number of function calls during solution"""
 
-    neqns: int = -1
+    n_equality_constraints: int = -1
     """number of equality constraints to be satisfied"""
 
     nfev1: int = 0
diff --git a/tests/integration/data/large_tokamak_eval.IN.DAT b/tests/integration/data/large_tokamak_eval.IN.DAT
index 87ffdd82f5..5c60b545d2 100644
--- a/tests/integration/data/large_tokamak_eval.IN.DAT
+++ b/tests/integration/data/large_tokamak_eval.IN.DAT
@@ -3,7 +3,7 @@ i_process_run_mode  = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
-neqns = 2
+n_equality_constraints = 2
 
 * Equalities
 icc = 1 * Beta
diff --git a/tests/integration/test_vmcon.py b/tests/integration/test_vmcon.py
index e5ef992681..20ad58ead2 100644
--- a/tests/integration/test_vmcon.py
+++ b/tests/integration/test_vmcon.py
@@ -432,12 +432,12 @@ def get_case1():
     case = Case("1", Evaluator1())
 
     # Set up solver args for this case
-    neqns = 1
+    n_equality_constraints = 1
     nineqns = 1
     case.solver_args.x[0:2] = 2.0e0
     case.solver_args.n = 2
-    case.solver_args.m = neqns + nineqns
-    case.solver_args.meq = neqns
+    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.meq = n_equality_constraints
 
     # Expected values
     case.exp.x = np.array([8.228756e-1, 9.114378e-1])
@@ -466,11 +466,11 @@ def get_case2():
     case = Case("2", Evaluator2())
 
     # Solver args for this case
-    neqns = 0
+    n_equality_constraints = 0
     nineqns = 2
     case.solver_args.n = 2
-    case.solver_args.m = neqns + nineqns
-    case.solver_args.meq = neqns
+    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.meq = n_equality_constraints
     case.solver_args.x[0:2] = 2.0e0
 
     # Expected values
@@ -503,11 +503,11 @@ def get_case3():
     case = Case("3", Evaluator3())
 
     # Solver args for this case
-    neqns = 1
+    n_equality_constraints = 1
     nineqns = 1
     case.solver_args.n = 2
-    case.solver_args.m = neqns + nineqns
-    case.solver_args.meq = neqns
+    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.meq = n_equality_constraints
     case.solver_args.x[0:2] = 2.0e0
 
     # Expected values
@@ -537,11 +537,11 @@ def get_case4():
     case = Case("4", Evaluator4())
 
     # Set up vmcon values for this case
-    neqns = 1
+    n_equality_constraints = 1
     nineqns = 0
     case.solver_args.n = 2
-    case.solver_args.m = neqns + nineqns
-    case.solver_args.meq = neqns
+    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.meq = n_equality_constraints
     case.solver_args.xtol = 2.0e-8
     case.solver_args.x[0:2] = 1.0e0
     # N.B. results can flip to minimum instead of maximum
@@ -579,11 +579,11 @@ def get_case5():
     case.solver_args = SolverArgs(n=1)
 
     # Set up vmcon values for this case
-    neqns = 1
+    n_equality_constraints = 1
     nineqns = 0
     case.solver_args.n = 1
-    case.solver_args.m = neqns + nineqns
-    case.solver_args.meq = neqns
+    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.meq = n_equality_constraints
     case.solver_args.x = np.array([
         5.0
     ])  # Try different values, e.g. 5.0, 2.0, 1.0, 0.0...
diff --git a/tests/regression/input_files/IFE.IN.DAT b/tests/regression/input_files/IFE.IN.DAT
index e4e602dd55..ba668e69f3 100644
--- a/tests/regression/input_files/IFE.IN.DAT
+++ b/tests/regression/input_files/IFE.IN.DAT
@@ -9,7 +9,7 @@
 
 *---------------Constraint Equations---------------*
 
-neqns = 0              *No equality constraints
+n_equality_constraints = 0              *No equality constraints
 icc = 16               *Net electric power lower limit
 
 *---------------Iteration Variables----------------*
diff --git a/tests/regression/input_files/helias_5b.IN.DAT b/tests/regression/input_files/helias_5b.IN.DAT
index 757479601d..ad5bb288f9 100644
--- a/tests/regression/input_files/helias_5b.IN.DAT
+++ b/tests/regression/input_files/helias_5b.IN.DAT
@@ -9,7 +9,7 @@
 
 *---------------Constraint Equations---------------*
 
-neqns = 3               *number of equalities
+n_equality_constraints = 3               *number of equalities
 
 
 *--------------- equalities
diff --git a/tests/regression/input_files/large_tokamak_eval.IN.DAT b/tests/regression/input_files/large_tokamak_eval.IN.DAT
index 3a2210a5a6..efc4c37dd2 100644
--- a/tests/regression/input_files/large_tokamak_eval.IN.DAT
+++ b/tests/regression/input_files/large_tokamak_eval.IN.DAT
@@ -3,7 +3,7 @@ i_process_run_mode  = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
-neqns = 2
+n_equality_constraints = 2
 
 * Equalities
 icc = 1 * Beta
diff --git a/tests/regression/input_files/large_tokamak_nof.IN.DAT b/tests/regression/input_files/large_tokamak_nof.IN.DAT
index b2f325a631..828a3a6e34 100644
--- a/tests/regression/input_files/large_tokamak_nof.IN.DAT
+++ b/tests/regression/input_files/large_tokamak_nof.IN.DAT
@@ -18,8 +18,8 @@ i_figure_merit = 1
 epsvmc = 1e-7
 
 * Number of equality constraints
-* (the first neqns icc=... statements are equality constraints)
-neqns = 3
+* (the first n_equality_constraints icc=... statements are equality constraints)
+n_equality_constraints = 3
 
 * Maximum number of solver iterations
 maxcal = 100
diff --git a/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT b/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
index a9b34bd7f7..c509d2339d 100644
--- a/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
+++ b/tests/regression/input_files/low_aspect_ratio_DEMO.IN.DAT
@@ -33,7 +33,7 @@ i_figure_merit   = -14 * Switch for figure-of-merit (see lablmm for descriptions
 * DESCRIPTION:   Switch for Figure-of-Merit (1: Minimise major radius)
 * JUSTIFICATION: Aim to minimise major radius
 
-neqns = 4
+n_equality_constraints = 4
 * DESCRIPTION:   No of equality constraints
 * JUSTIFICATION: 
 
diff --git a/tests/regression/input_files/spherical_tokamak_eval.IN.DAT b/tests/regression/input_files/spherical_tokamak_eval.IN.DAT
index dd74bbf4e6..93f3541265 100644
--- a/tests/regression/input_files/spherical_tokamak_eval.IN.DAT
+++ b/tests/regression/input_files/spherical_tokamak_eval.IN.DAT
@@ -3,7 +3,7 @@ i_process_run_mode = -2
 
 *---------------Constraint Equations---------------*
 * Define number of equality constraints
-neqns = 3
+n_equality_constraints = 3
 
 * Equalities
 icc = 1 * Beta
diff --git a/tests/regression/input_files/st_regression.IN.DAT b/tests/regression/input_files/st_regression.IN.DAT
index 5e52ccad64..a34de1f2e9 100644
--- a/tests/regression/input_files/st_regression.IN.DAT
+++ b/tests/regression/input_files/st_regression.IN.DAT
@@ -55,8 +55,8 @@ i_figure_merit = -5
 * DESCRIPTION:   Switch for Figure-of-Merit 
 * JUSTIFICATION: Selected optimisation
 
-neqns = 3
-* DESCRIPTION:   Number of equality constraints (the first neqns icc = ... statements are considered equality)
+n_equality_constraints = 3
+* DESCRIPTION:   Number of equality constraints (the first n_equality_constraints icc = ... statements are considered equality)
 * JUSTIFICATION: 3 equality (consistency) equations
 
 *________________________________________________________________________*
diff --git a/tests/regression/input_files/stellarator_helias.IN.DAT b/tests/regression/input_files/stellarator_helias.IN.DAT
index 3fcb03beb5..73480c5d80 100644
--- a/tests/regression/input_files/stellarator_helias.IN.DAT
+++ b/tests/regression/input_files/stellarator_helias.IN.DAT
@@ -9,7 +9,7 @@
 
 *---------------Constraint Equations---------------*
 
-neqns = 2               *number of equalities
+n_equality_constraints = 2               *number of equalities
 
 
 *--------------- equalities

From eaf563d459e4c7ca38d74d04e6f831bc54abb03e Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:12:05 +0100
Subject: [PATCH 06/13] Rename `nineqns` to `n_inequality_constraints` for
 consistency with style guide

---
 process/core/init.py               | 77 ++++++++++++++++++++++--------
 process/core/input.py              |  2 +-
 process/data_structure/numerics.py |  4 +-
 tests/integration/test_vmcon.py    | 20 ++++----
 4 files changed, 69 insertions(+), 34 deletions(-)

diff --git a/process/core/init.py b/process/core/init.py
index e72991befe..da82066699 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -179,12 +179,12 @@ def run_summary(data: DataStructure):
         )
         process_output.ocmmnt(
             outfile,
-            f"Inequality constraints : {data.numerics.nineqns}",
+            f"Inequality constraints : {data.numerics.n_inequality_constraints}",
         )
         process_output.ocmmnt(
             outfile,
             f"Total constraints : "
-            f"{data.numerics.nineqns + data.numerics.n_equality_constraints}",
+            f"{data.numerics.n_inequality_constraints + data.numerics.n_equality_constraints}",
         )
         process_output.ocmmnt(outfile, f"Iteration variables : {data.numerics.nvar}")
         # If optimising, write objective function and convergence parameter
@@ -305,21 +305,25 @@ def check_process(inputs, data):  # noqa: ARG001
         )
 
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 0
     ).any():
         raise ProcessValidationError(
             "The number of constraints specified is smaller than the number stated"
-            " in n_equality_constraints+nineqns",
+            " in n_equality_constraints+n_inequality_constraints",
             n_equality_constraints=data.numerics.n_equality_constraints,
-            nineqns=data.numerics.nineqns,
+            n_inequality_constraints=data.numerics.n_inequality_constraints,
         )
 
     # Deprecate constraints
     for depcrecated_constraint in [3, 4, 10, 74, 42]:
         if (
             data.numerics.icc[
-                : data.numerics.n_equality_constraints + data.numerics.nineqns
+                : data.numerics.n_equality_constraints
+                + data.numerics.n_inequality_constraints
             ]
             == depcrecated_constraint
         ).any():
@@ -329,7 +333,10 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # MDK Report error if constraint 63 is used with old vacuum model
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 63
     ).any() and data.vacuum.i_vacuum_pumping != "simple":
         raise ProcessValidationError(
@@ -506,7 +513,8 @@ def check_process(inputs, data):  # noqa: ARG001
             data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION
             and not (
                 data.numerics.icc[
-                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                    : data.numerics.n_equality_constraints
+                    + data.numerics.n_inequality_constraints
                 ]
                 == 81
             ).any()
@@ -529,10 +537,16 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use Psep/R and PsepB/qAR limits at the same time
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 68
     ).any() and (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 56
     ).any():
         raise ProcessValidationError(
@@ -551,7 +565,10 @@ def check_process(inputs, data):  # noqa: ARG001
         )
 
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 78
     ).any():
         # If Reinke criterion is used temp_plasma_separatrix_kev is calculated and
@@ -567,7 +584,8 @@ def check_process(inputs, data):  # noqa: ARG001
         if (data.physics.i_l_h_threshold != 6) or (
             not (
                 data.numerics.icc[
-                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                    : data.numerics.n_equality_constraints
+                    + data.numerics.n_inequality_constraints
                 ]
                 == 15
             ).any()
@@ -708,7 +726,8 @@ def check_process(inputs, data):  # noqa: ARG001
             data.tfcoil.i_tf_sup == TFConductorModel.HELIUM_COOLED_ALUMINIUM
             and (
                 data.numerics.icc[
-                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                    : data.numerics.n_equality_constraints
+                    + data.numerics.n_inequality_constraints
                 ]
                 == 85
             ).any()
@@ -784,7 +803,8 @@ def check_process(inputs, data):  # noqa: ARG001
         # Constraint 10 is dedicated to ST designs with demountable joints
         if (
             data.numerics.icc[
-                : data.numerics.n_equality_constraints + data.numerics.nineqns
+                : data.numerics.n_equality_constraints
+                + data.numerics.n_inequality_constraints
             ]
             == 10
         ).any():
@@ -824,13 +844,15 @@ def check_process(inputs, data):  # noqa: ARG001
         and (
             (
                 data.numerics.icc[
-                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                    : data.numerics.n_equality_constraints
+                    + data.numerics.n_inequality_constraints
                 ]
                 == 31
             ).any()
             or (
                 data.numerics.icc[
-                    : data.numerics.n_equality_constraints + data.numerics.nineqns
+                    : data.numerics.n_equality_constraints
+                    + data.numerics.n_inequality_constraints
                 ]
                 == 32
             ).any()
@@ -1204,7 +1226,10 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use temperature margin constraint with REBCO TF coils
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 36
     ).any() and (
         SuperconductorModel(data.tfcoil.i_tf_sc_mat).sc_type
@@ -1216,7 +1241,10 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use temperature margin constraint with REBCO CS coils
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 60
     ).any() and data.pf_coil.i_cs_superconductor == 8:
         raise ProcessValidationError(
@@ -1229,7 +1257,10 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Cannot use TF coil strain limit if i_str_wp is off:
     if (
-        data.numerics.icc[: data.numerics.n_equality_constraints + data.numerics.nineqns]
+        data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
         == 88
     ).any() and data.tfcoil.i_str_wp == 0:
         raise ProcessValidationError("Can't use constraint 88 if i_strain_tf == 0")
@@ -1246,9 +1277,13 @@ def set_active_constraints(data: DataStructure):
     if data.numerics.n_equality_constraints < 0:
         # The value of n_equality_constraints has not been set in the input file.
         # Default = 0.
-        data.numerics.n_equality_constraints = num_constraints - data.numerics.nineqns
+        data.numerics.n_equality_constraints = (
+            num_constraints - data.numerics.n_inequality_constraints
+        )
     else:
-        data.numerics.nineqns = num_constraints - data.numerics.n_equality_constraints
+        data.numerics.n_inequality_constraints = (
+            num_constraints - data.numerics.n_equality_constraints
+        )
 
 
 def set_device_type(data: DataStructure):
diff --git a/process/core/input.py b/process/core/input.py
index d836de9312..811eb26760 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -156,7 +156,7 @@ def bounds(self) -> tuple[NumberType | None, NumberType | None]:
     "n_equality_constraints": InputVariable(
         "numerics", int, range=(0, ConstraintManager.num_constraints())
     ),
-    "nineqns": InputVariable(
+    "n_inequality_constraints": InputVariable(
         "numerics", int, range=(0, ConstraintManager.num_constraints())
     ),
     "alphaj": InputVariable("physics", float, range=(0.0, 10.0)),
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 9c6a382d34..9f823aae51 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -158,7 +158,7 @@ class NumericsData:
     """
 
     n_constraints: int = 0
-    """Total number of constraints (n_equality_constraints + nineqns)"""
+    """Total number of constraints (n_equality_constraints + n_inequality_constraints)"""
 
     ncalls: int = 0
     """number of function calls during solution"""
@@ -172,7 +172,7 @@ class NumericsData:
     nfev2: int = 0
     """number of calls to FCNVMC1 (VMCON function caller) made"""
 
-    nineqns: int = 0
+    n_inequality_constraints: int = 0
     """number of inequality constraints VMCON must satisfy
     (leave at zero for now)
     """
diff --git a/tests/integration/test_vmcon.py b/tests/integration/test_vmcon.py
index 20ad58ead2..81eceac1d3 100644
--- a/tests/integration/test_vmcon.py
+++ b/tests/integration/test_vmcon.py
@@ -433,10 +433,10 @@ def get_case1():
 
     # Set up solver args for this case
     n_equality_constraints = 1
-    nineqns = 1
+    n_inequality_constraints = 1
     case.solver_args.x[0:2] = 2.0e0
     case.solver_args.n = 2
-    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.m = n_equality_constraints + n_inequality_constraints
     case.solver_args.meq = n_equality_constraints
 
     # Expected values
@@ -467,9 +467,9 @@ def get_case2():
 
     # Solver args for this case
     n_equality_constraints = 0
-    nineqns = 2
+    n_inequality_constraints = 2
     case.solver_args.n = 2
-    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.m = n_equality_constraints + n_inequality_constraints
     case.solver_args.meq = n_equality_constraints
     case.solver_args.x[0:2] = 2.0e0
 
@@ -504,9 +504,9 @@ def get_case3():
 
     # Solver args for this case
     n_equality_constraints = 1
-    nineqns = 1
+    n_inequality_constraints = 1
     case.solver_args.n = 2
-    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.m = n_equality_constraints + n_inequality_constraints
     case.solver_args.meq = n_equality_constraints
     case.solver_args.x[0:2] = 2.0e0
 
@@ -538,9 +538,9 @@ def get_case4():
 
     # Set up vmcon values for this case
     n_equality_constraints = 1
-    nineqns = 0
+    n_inequality_constraints = 0
     case.solver_args.n = 2
-    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.m = n_equality_constraints + n_inequality_constraints
     case.solver_args.meq = n_equality_constraints
     case.solver_args.xtol = 2.0e-8
     case.solver_args.x[0:2] = 1.0e0
@@ -580,9 +580,9 @@ def get_case5():
 
     # Set up vmcon values for this case
     n_equality_constraints = 1
-    nineqns = 0
+    n_inequality_constraints = 0
     case.solver_args.n = 1
-    case.solver_args.m = n_equality_constraints + nineqns
+    case.solver_args.m = n_equality_constraints + n_inequality_constraints
     case.solver_args.meq = n_equality_constraints
     case.solver_args.x = np.array([
         5.0

From 051132badca730a6d1990519c7faa336f12d0217 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:12:51 +0100
Subject: [PATCH 07/13] Rename `ncalls` to `n_model_calls` for consistency with
 style guide

---
 process/core/caller.py             | 2 +-
 process/data_structure/numerics.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/process/core/caller.py b/process/core/caller.py
index dabc5054d8..875c09d686 100644
--- a/process/core/caller.py
+++ b/process/core/caller.py
@@ -262,7 +262,7 @@ def _call_models_once(self, xc: np.ndarray):
         nvars = len(xc)
 
         # Increment the call counter
-        self.data.numerics.ncalls += 1
+        self.data.numerics.n_model_calls += 1
 
         # Convert variables
         set_scaled_iteration_variable(xc, nvars, self.data)
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 9f823aae51..7bec9581c0 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -160,7 +160,7 @@ class NumericsData:
     n_constraints: int = 0
     """Total number of constraints (n_equality_constraints + n_inequality_constraints)"""
 
-    ncalls: int = 0
+    n_model_calls: int = 0
     """number of function calls during solution"""
 
     n_equality_constraints: int = -1

From 1da9af85c8dcc833102a11d26c9c3b4907e3b177 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:15:15 +0100
Subject: [PATCH 08/13] Rename `nvar` to `n_iteration_variables` for
 consistency with style guide

---
 documentation/source/usage/troubleshooting.md |  6 +--
 process/core/caller.py                        |  2 +-
 process/core/init.py                          | 52 ++++++++++---------
 process/core/input.py                         |  6 +--
 process/core/io/in_dat/base.py                |  2 +-
 process/core/io/mfile/base.py                 |  2 +-
 process/core/io/plot/summary.py               |  4 +-
 process/core/solver/iteration_variables.py    |  4 +-
 process/core/solver/solver.py                 |  4 +-
 process/data_structure/numerics.py            |  2 +-
 process/main.py                               |  2 +-
 process/models/build.py                       |  7 ++-
 12 files changed, 50 insertions(+), 43 deletions(-)

diff --git a/documentation/source/usage/troubleshooting.md b/documentation/source/usage/troubleshooting.md
index b9805e2c54..8ef92e0e75 100644
--- a/documentation/source/usage/troubleshooting.md
+++ b/documentation/source/usage/troubleshooting.md
@@ -44,9 +44,9 @@ necessity brief, and so cannot promise to lead to a more successful outcome.
 ### Optimisation problems
 
 On reflection it is perhaps surprising that PROCESS ever does manage to find the global minimum 
-figure of merit value, if there are `nvar` iteration variables active the search is 
-over `nvar`-dimensional parameter space, in which there may be many shallow minima of approximately 
-equal depth. Remember that `nvar` is usually of the order of twenty.
+figure of merit value, if there are `n_iteration_variables` iteration variables active the search is 
+over `n_iteration_variables`-dimensional parameter space, in which there may be many shallow minima of approximately 
+equal depth. Remember that `n_iteration_variables` is usually of the order of twenty.
 
 The machine found by PROCESS may not, therefore, be the absolute optimal device. It is quite easy 
 to have two or more solutions, with results only a few percent different, but a long way apart in 
diff --git a/process/core/caller.py b/process/core/caller.py
index 875c09d686..463d041d80 100644
--- a/process/core/caller.py
+++ b/process/core/caller.py
@@ -508,7 +508,7 @@ def write_output_files(
     ifail : int
         solver return code
     """
-    n = data.numerics.nvar
+    n = data.numerics.n_iteration_variables
     x = data.numerics.xcm[:n]
     # Call models, ensuring output mfiles are fully idempotent
     caller = Caller(models, data)
diff --git a/process/core/init.py b/process/core/init.py
index da82066699..5ec28d7557 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -186,7 +186,9 @@ def run_summary(data: DataStructure):
             f"Total constraints : "
             f"{data.numerics.n_inequality_constraints + data.numerics.n_equality_constraints}",
         )
-        process_output.ocmmnt(outfile, f"Iteration variables : {data.numerics.nvar}")
+        process_output.ocmmnt(
+            outfile, f"Iteration variables : {data.numerics.n_iteration_variables}"
+        )
         # If optimising, write objective function and convergence parameter
         if data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION:
             process_output.ocmmnt(
@@ -259,25 +261,25 @@ def check_process(inputs, data):  # noqa: ARG001
         See individual ProcessValidationError instances for more details.
     """
     # Check that there are sufficient iteration variables
-    if data.numerics.nvar < data.numerics.n_equality_constraints:
+    if data.numerics.n_iteration_variables < data.numerics.n_equality_constraints:
         raise ProcessValidationError(
             "Insufficient iteration variables to solve the problem! NVAR < NEQNS",
-            nvar=data.numerics.nvar,
+            n_iteration_variables=data.numerics.n_iteration_variables,
             n_equality_constraints=data.numerics.n_equality_constraints,
         )
 
     # Check that sufficient elements of ixc and icc have been specified
-    if (data.numerics.ixc[: data.numerics.nvar] == 0).any():
+    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 0).any():
         raise ProcessValidationError(
             "The number of iteration variables specified is smaller than the number"
             " stated in ixc",
-            nvar=data.numerics.nvar,
+            n_iteration_variables=data.numerics.n_iteration_variables,
         )
 
     # Check that dr_tf_wp_with_insulation (ixc = 140) and dr_tf_inboard (ixc = 13)
     # are not being used simultaneously as iteration variables
-    if (data.numerics.ixc[: data.numerics.nvar] == 13).any() and (
-        data.numerics.ixc[: data.numerics.nvar] == 140
+    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 13).any() and (
+        data.numerics.ixc[: data.numerics.n_iteration_variables] == 140
     ).any():
         raise ProcessValidationError(
             "Iteration variables 13 and 140 cannot be used simultaneously",
@@ -285,7 +287,7 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Can't use c_tf_turn as iteration var, constraint or
     # input if i_tf_turns_integer == 1
-    if (data.numerics.ixc[: data.numerics.nvar] == 60).any() and TFWPIntegerTurnType(
+    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 60).any() and TFWPIntegerTurnType(
         data.tfcoil.i_tf_turns_integer
     ) == TFWPIntegerTurnType.INTEGER:
         raise ProcessValidationError(
@@ -296,8 +298,8 @@ def check_process(inputs, data):  # noqa: ARG001
         )
 
     # Can't have icc 77 and ixc 60 at the same time
-    if (data.numerics.ixc[: data.numerics.nvar] == 60).any() and (
-        data.numerics.icc[: data.numerics.nvar] == 77
+    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 60).any() and (
+        data.numerics.icc[: data.numerics.n_iteration_variables] == 77
     ).any():
         raise ProcessValidationError(
             "Cannot use iteration variable 60 (TF coil current per turn, c_tf_turn) and "
@@ -382,7 +384,7 @@ def check_process(inputs, data):  # noqa: ARG001
     # As the current density is now calculated from b_plasma_toroidal_on_axis
     # without constraint 10
 
-    if (data.numerics.ixc[: data.numerics.nvar] == 12).any():
+    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 12).any():
         raise ProcessValidationError(
             "The 1/R toroidal B field dependency constraint is being depreciated"
         )
@@ -437,7 +439,7 @@ def check_process(inputs, data):  # noqa: ARG001
 
         if (
             data.numerics.i_process_run_mode == PROCESSRunMode.OPTIMISATION
-            and (data.numerics.ixc[: data.numerics.nvar] == 4).any()
+            and (data.numerics.ixc[: data.numerics.n_iteration_variables] == 4).any()
             and data.numerics.boundl[3] < data.physics.temp_plasma_pedestal_kev * 1.001
         ):
             logger.warning(
@@ -519,7 +521,7 @@ def check_process(inputs, data):  # noqa: ARG001
                 == 81
             ).any()
         ):
-            if (data.numerics.ixc[: data.numerics.nvar] == 145).any():
+            if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 145).any():
                 logger.warning(
                     "nd_plasma_pedestal_electron set with"
                     " f_nd_plasma_pedestal_greenwald"
@@ -527,7 +529,7 @@ def check_process(inputs, data):  # noqa: ARG001
                     " eq 81 (nd_plasma_pedestal_electron<nd_plasma_electron_on_axis)",
                     stacklevel=2,
                 )
-            if (data.numerics.ixc[: data.numerics.nvar] == 6).any():
+            if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 6).any():
                 logger.warning(
                     "nd_plasma_electrons_vol_avg used as iteration variable without"
                     " constraint 81"
@@ -554,7 +556,9 @@ def check_process(inputs, data):  # noqa: ARG001
         )
 
     # if lower bound of f_nd_plasma_pedestal_greenwald < f_nd_plasma_separatrix_greenwald
-    if (data.numerics.ixc[: data.numerics.nvar] == 145).any() and data.numerics.boundl[
+    if (
+        data.numerics.ixc[: data.numerics.n_iteration_variables] == 145
+    ).any() and data.numerics.boundl[
         144
     ] < data.physics.f_nd_plasma_separatrix_greenwald:
         raise ProcessValidationError(
@@ -573,7 +577,7 @@ def check_process(inputs, data):  # noqa: ARG001
     ).any():
         # If Reinke criterion is used temp_plasma_separatrix_kev is calculated and
         # cannot be an iteration variable
-        if (data.numerics.ixc[: data.numerics.nvar] == 119).any():
+        if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 119).any():
             raise ProcessValidationError(
                 "REINKE IMPURITY MODEL: temp_plasma_separatrix_kev is calculated and "
                 "cannot be an iteration variable for the Reinke model"
@@ -657,7 +661,7 @@ def check_process(inputs, data):  # noqa: ARG001
 
             # Check if conductor upper limit is properly set to 50 K or below
             if (
-                data.numerics.ixc[: data.numerics.nvar] == 20
+                data.numerics.ixc[: data.numerics.n_iteration_variables] == 20
             ).any() and data.numerics.boundu[19] < 273.15:
                 raise ProcessValidationError(
                     "Too low CP conductor temperature (temp_cp_average)."
@@ -692,7 +696,7 @@ def check_process(inputs, data):  # noqa: ARG001
 
             # Check if conductor upper limit is properly set to 50 K or below
             if (
-                data.numerics.ixc[: data.numerics.nvar] == 20
+                data.numerics.ixc[: data.numerics.n_iteration_variables] == 20
             ).any() and data.numerics.boundu[19] > 50.0:
                 raise ProcessValidationError(
                     "Too large CP conductor temperature (temp_cp_average). Upper limit"
@@ -750,7 +754,7 @@ def check_process(inputs, data):  # noqa: ARG001
         # Checking the CP TF top radius
         if (
             abs(data.build.r_cp_top) > 0
-            or (data.numerics.ixc[: data.numerics.nvar] == 174).any()
+            or (data.numerics.ixc[: data.numerics.n_iteration_variables] == 174).any()
         ) and data.build.i_r_cp_top != 1:
             raise ProcessValidationError(
                 "To set the TF CP top value, you must use i_r_cp_top = 1"
@@ -827,9 +831,9 @@ def check_process(inputs, data):  # noqa: ARG001
     if (
         (
             not (
-                (data.numerics.ixc[: data.numerics.nvar] == 16).any()
-                or (data.numerics.ixc[: data.numerics.nvar] == 29).any()
-                or (data.numerics.ixc[: data.numerics.nvar] == 42).any()
+                (data.numerics.ixc[: data.numerics.n_iteration_variables] == 16).any()
+                or (data.numerics.ixc[: data.numerics.n_iteration_variables] == 29).any()
+                or (data.numerics.ixc[: data.numerics.n_iteration_variables] == 42).any()
             )
         )  # No dr_bore,dr_cs_tf_gap, dr_cs iteration
         and (
@@ -1029,7 +1033,7 @@ def check_process(inputs, data):  # noqa: ARG001
     # is large enough
     # To contains the insulation, cooling and the support structure
     # Rem : Only verified if the WP thickness is used
-    if (data.numerics.ixc[: data.numerics.nvar] == 140).any():
+    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 140).any():
         # Minimal WP thickness
         if data.tfcoil.i_tf_sup == TFConductorModel.SUPERCONDUCTING:
             dr_tf_wp_min = 2.0 * (
@@ -1040,7 +1044,7 @@ def check_process(inputs, data):  # noqa: ARG001
             )
 
             # Steel conduit thickness (can be an iteration variable)
-            if (data.numerics.ixc[: data.numerics.nvar] == 58).any():
+            if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 58).any():
                 dr_tf_wp_min += 2.0 * data.numerics.boundl[57]
             else:
                 dr_tf_wp_min += 2.0 * data.tfcoil.dx_tf_turn_steel
diff --git a/process/core/input.py b/process/core/input.py
index 811eb26760..017247f206 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -37,8 +37,8 @@
 def _ixc_additional_actions(
     _name, value: int, _array_index, _config, data: DataStructure
 ):
-    data.numerics.ixc[data.numerics.nvar] = value
-    data.numerics.nvar += 1
+    data.numerics.ixc[data.numerics.n_iteration_variables] = value
+    data.numerics.n_iteration_variables += 1
 
 
 def _icc_additional_actions(
@@ -1194,7 +1194,7 @@ def parse_input_file(data_structure_obj: DataStructure):
     """
     # These get incremented when reading the file, so need
     # to ensure they are 0 before we parse the file
-    data_structure_obj.numerics.nvar = 0
+    data_structure_obj.numerics.n_iteration_variables = 0
     data_structure_obj.numerics.n_constraints = 0
 
     input_file_path = (
diff --git a/process/core/io/in_dat/base.py b/process/core/io/in_dat/base.py
index c6cc8f0353..21be3d153c 100644
--- a/process/core/io/in_dat/base.py
+++ b/process/core/io/in_dat/base.py
@@ -387,7 +387,7 @@ def get_parameters(data, use_string_values=True):
     # dict of all parameters set in input file, grouped by module
     # Include n_equality_constraints to allow eq and ineq constraints to be defined in
     # produced IN.DAT
-    exclusions = ["nvar", "icc", "ixc"]
+    exclusions = ["n_iteration_variables", "icc", "ixc"]
     # Parameters to exclude
 
     # Change module keys from DICT_MODULE: replace spaces with underscores and
diff --git a/process/core/io/mfile/base.py b/process/core/io/mfile/base.py
index 568a91e047..51aa59fd22 100644
--- a/process/core/io/mfile/base.py
+++ b/process/core/io/mfile/base.py
@@ -650,7 +650,7 @@ def get_mfile_initial_ixc_values(file_path: Path, data: DataStructure):
     iteration_variable_names = []
     iteration_variable_values = []
 
-    for i in range(data.numerics.nvar):
+    for i in range(data.numerics.n_iteration_variables):
         ivar = data.numerics.ixc[i].item()
 
         itv = iteration_variables.ITERATION_VARIABLES[ivar]
diff --git a/process/core/io/plot/summary.py b/process/core/io/plot/summary.py
index 8a6035d2de..4af450e786 100644
--- a/process/core/io/plot/summary.py
+++ b/process/core/io/plot/summary.py
@@ -10874,7 +10874,7 @@ def plot_iteration_variables(axis: plt.Axes, m_file: MFile, scan: int):
 
     """
     # Get total number of iteration variables
-    n_itvars = int(m_file.get("nvar", scan=scan))
+    n_itvars = int(m_file.get("n_iteration_variables", scan=scan))
 
     y_labels = []
     y_pos = []
@@ -12077,7 +12077,7 @@ def plot_cover_page(
     optmisation_switch = int(mfile.get("i_process_run_mode", scan=-1))
     minmax_switch = mfile.get("i_figure_merit", scan=-1) or "N/A"
     ifail = mfile.get("ifail", scan=-1)
-    nvars = mfile.get("nvar", scan=-1)
+    nvars = mfile.get("n_iteration_variables", scan=-1)
     # Objective_function_name
     objf_name = mfile.get("objf_name", scan=-1)
     # Square_root_of_the_sum_of_squares_of_the_constraint_residuals
diff --git a/process/core/solver/iteration_variables.py b/process/core/solver/iteration_variables.py
index c40f932ec1..d1df7c6feb 100644
--- a/process/core/solver/iteration_variables.py
+++ b/process/core/solver/iteration_variables.py
@@ -283,7 +283,7 @@ def load_iteration_variables(data):
     ProcessValueError
         If iteration variable is missing
     """
-    for i in range(data.numerics.nvar):
+    for i in range(data.numerics.n_iteration_variables):
         variable_index = data.numerics.ixc[i]
         iteration_variable = ITERATION_VARIABLES[variable_index]
 
@@ -405,7 +405,7 @@ def set_scaled_iteration_variable(xc, nn: int, data: DataStructure):
 
 def load_scaled_bounds(data: DataStructure):
     """Sets the scaled bounds of the iteration variables."""
-    for i in range(data.numerics.nvar):
+    for i in range(data.numerics.n_iteration_variables):
         variable_index = data.numerics.ixc[i] - 1
         data.numerics.itv_scaled_lower_bounds[i] = (
             data.numerics.boundl[variable_index] * data.numerics.scale[i]
diff --git a/process/core/solver/solver.py b/process/core/solver/solver.py
index 513bebeafa..fbfbde4f19 100644
--- a/process/core/solver/solver.py
+++ b/process/core/solver/solver.py
@@ -193,7 +193,7 @@ def solve(self) -> SolverOutputCondition:
 
         bb = None
         if self.b is not None:
-            bb = np.identity(self.data.numerics.nvar) * self.b
+            bb = np.identity(self.data.numerics.n_iteration_variables) * self.b
 
         def _solver_callback(i: int, _result, _x, convergence_param: float):
             self.data.numerics.nviter = i + 1
@@ -273,7 +273,7 @@ def _ineq_cons_satisfied(
         except ValueError:
             itervar_name_list = ""
             for count, iter_var in enumerate(
-                self.data.numerics.ixc[: self.data.numerics.nvar]
+                self.data.numerics.ixc[: self.data.numerics.n_iteration_variables]
             ):
                 itervar_name = self.data.numerics.lablxc[iter_var - 1]
                 itervar_name_list += f"{count}: {itervar_name} \n"
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 7bec9581c0..0122e72a6d 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -177,7 +177,7 @@ class NumericsData:
     (leave at zero for now)
     """
 
-    nvar: int = 0
+    n_iteration_variables: int = 0
     """number of iteration variables to use"""
 
     nviter: int = 0
diff --git a/process/main.py b/process/main.py
index 1bf577bfa1..4f2c7ccfa8 100644
--- a/process/main.py
+++ b/process/main.py
@@ -433,7 +433,7 @@ def initialise(self):
 
         # Order optimisation parameters (arbitrary order in input file)
         # Ensures consistency and makes output comparisons more straightforward
-        n = int(self.data.numerics.nvar)
+        n = int(self.data.numerics.n_iteration_variables)
         # [:n] as array always at max size: contains 0s
         self.data.numerics.ixc[:n].sort()
 
diff --git a/process/models/build.py b/process/models/build.py
index 7fa2b7b3e3..d0f86fa049 100644
--- a/process/models/build.py
+++ b/process/models/build.py
@@ -1681,7 +1681,7 @@ def calculate_radial_build(self, output: bool):
         # Issue #514 Radial dimensions of inboard leg
         # Calculate self.data.build.dr_tf_inboard if
         # self.data.tfcoil.dr_tf_wp_with_insulation is an iteration variable (140)
-        if 140 in self.data.numerics.ixc[0 : self.data.numerics.nvar]:
+        if 140 in self.data.numerics.ixc[0 : self.data.numerics.n_iteration_variables]:
             self.data.build.dr_tf_inboard = (
                 self.data.tfcoil.dr_tf_wp_with_insulation
                 + self.data.tfcoil.dr_tf_plasma_case
@@ -1736,7 +1736,10 @@ def calculate_radial_build(self, output: bool):
 
         # WP radial thickness [m]
         # Calculated only if not used as an iteration variable
-        if 140 not in self.data.numerics.ixc[0 : self.data.numerics.nvar]:
+        if (
+            140
+            not in self.data.numerics.ixc[0 : self.data.numerics.n_iteration_variables]
+        ):
             self.data.tfcoil.dr_tf_wp_with_insulation = (
                 self.data.build.dr_tf_inboard
                 - self.data.tfcoil.dr_tf_plasma_case

From eef77ef8a8d21640e1617900c166de2b18cdfa4f Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:16:29 +0100
Subject: [PATCH 09/13] Rename `nviter` to `n_solver_iterations` for
 consistency with style guide

---
 process/core/io/plot/summary.py              | 4 ++--
 process/core/solver/evaluators.py            | 4 ++--
 process/core/solver/solver.py                | 2 +-
 process/core/solver/solver_handler.py        | 4 ++--
 process/data_structure/numerics.py           | 2 +-
 tests/regression/test_process_input_files.py | 2 +-
 6 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/process/core/io/plot/summary.py b/process/core/io/plot/summary.py
index 4af450e786..d87c486c88 100644
--- a/process/core/io/plot/summary.py
+++ b/process/core/io/plot/summary.py
@@ -12085,7 +12085,7 @@ def plot_cover_page(
     # VMCON_convergence_parameter
     convergence_parameter = mfile.get("convergence_parameter", scan=-1) or "N/A"
     # Number_of_optimising_solver_iterations
-    nviter = int(mfile.get("nviter", scan=-1)) or "N/A"
+    n_solver_iterations = int(mfile.get("n_solver_iterations", scan=-1)) or "N/A"
 
     # Objective name with minimising/maximising
     if isinstance(minmax_switch, str):
@@ -12163,7 +12163,7 @@ def plot_cover_page(
         f"• Number of Iteration Variables: {int(nvars)}\n"
         f"• Constraint Residuals (sqrt sum sq): {sqsumsq}\n"
         f"• Convergence Parameter: {convergence_parameter}\n"
-        f"• Solver Iterations: {nviter}\n"
+        f"• Solver Iterations: {n_solver_iterations}\n"
         f"• Runtime: {mfile.get('process_runtime', scan=-1):.6f} seconds"
     )
     axis.text(
diff --git a/process/core/solver/evaluators.py b/process/core/solver/evaluators.py
index 588ef4da25..9a672e1884 100644
--- a/process/core/solver/evaluators.py
+++ b/process/core/solver/evaluators.py
@@ -69,9 +69,9 @@ def fcnvmc1(self, _n, m, xv, ifail):
 
         sqsumconfsq = math.sqrt(summ)
         logger.debug("Key evaluator values:")
-        logger.debug(f"{self.data.numerics.nviter = }")
+        logger.debug(f"{self.data.numerics.n_solver_iterations = }")
         logger.debug(f"{(1 - (ifail % 7)) - 1 = }")
-        logger.debug(f"{(self.data.numerics.nviter % 2) - 1 = }")
+        logger.debug(f"{(self.data.numerics.n_solver_iterations % 2) - 1 = }")
         logger.debug(f"{self.data.physics.temp_plasma_electron_vol_avg_kev = }")
         logger.debug(f"{self.data.costs.coe = }")
         logger.debug(f"{self.data.physics.rmajor = }")
diff --git a/process/core/solver/solver.py b/process/core/solver/solver.py
index fbfbde4f19..25fbd624bf 100644
--- a/process/core/solver/solver.py
+++ b/process/core/solver/solver.py
@@ -196,7 +196,7 @@ def solve(self) -> SolverOutputCondition:
             bb = np.identity(self.data.numerics.n_iteration_variables) * self.b
 
         def _solver_callback(i: int, _result, _x, convergence_param: float):
-            self.data.numerics.nviter = i + 1
+            self.data.numerics.n_solver_iterations = i + 1
             self.data.globals.convergence_parameter = convergence_param
             print(
                 f"{i + 1} | Convergence Parameter: {convergence_param:.3E}",
diff --git a/process/core/solver/solver_handler.py b/process/core/solver/solver_handler.py
index ecd5059493..d731a11c95 100644
--- a/process/core/solver/solver_handler.py
+++ b/process/core/solver/solver_handler.py
@@ -83,10 +83,10 @@ def run(self):
             # If VMCON has exited with error code 5
             # (ifail = SolverOutputCondition.NO_SOLUTION) try another run using a
             # multiple of the identity matrix as input for the Hessian b(n,n)
-            # Only do this if VMCON has not iterated (nviter=1)
+            # Only do this if VMCON has not iterated (n_solver_iterations=1)
             if (
                 ifail == SolverOutputCondition.NO_SOLUTION
-                and self.data.numerics.nviter < 2
+                and self.data.numerics.n_solver_iterations < 2
             ):
                 print(
                     "VMCON error code = 5 (SolverOutputCondition.NO_SOLUTION). "
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index 0122e72a6d..fa2d6c2049 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -180,7 +180,7 @@ class NumericsData:
     n_iteration_variables: int = 0
     """number of iteration variables to use"""
 
-    nviter: int = 0
+    n_solver_iterations: int = 0
     """number of optimisation iterations performed"""
 
     icc: list[int] = field(
diff --git a/tests/regression/test_process_input_files.py b/tests/regression/test_process_input_files.py
index 342477da26..4a77f77fee 100644
--- a/tests/regression/test_process_input_files.py
+++ b/tests/regression/test_process_input_files.py
@@ -31,7 +31,7 @@
     "xcm",
     "convergence_parameter",
     "sqsumsq",
-    "nviter",
+    "n_solver_iterations",
     "commsg",
     "procver",
     r"sig_tf_r_max\(1\)",  # weird value, flips between 0 and very low?

From 165f89859f5b424d17d9f2fc16eb04f769fc56e5 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 28 Jul 2026 15:22:12 +0100
Subject: [PATCH 10/13] Add input variables to obsolete dictionary

---
 process/core/io/obsolete_vars.py   | 4 ++++
 process/data_structure/numerics.py | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/process/core/io/obsolete_vars.py b/process/core/io/obsolete_vars.py
index e096c85032..7227a4b773 100644
--- a/process/core/io/obsolete_vars.py
+++ b/process/core/io/obsolete_vars.py
@@ -474,6 +474,10 @@
     "f_nd_alpha_electron": "f_nd_alpha_thermal_electron",
     "cost_model": "i_cost_model",
     "t_conductor": "dx_tf_turn_conduit_full_average",
+    "ioptimz": "i_process_run_mode",
+    "minmax": "i_figure_merit",
+    "neqns": "n_equality_constraints",
+    "nineqns": "n_inequality_constraints",
 }
 
 OBS_VARS_HELP = {
diff --git a/process/data_structure/numerics.py b/process/data_structure/numerics.py
index fa2d6c2049..c45415f95b 100644
--- a/process/data_structure/numerics.py
+++ b/process/data_structure/numerics.py
@@ -147,11 +147,11 @@ def description(self):
 class NumericsData:
     """Dataclass holding numerics variables"""
 
-    i_process_run_mode: int | PROCESSRunMode = 1
+    i_process_run_mode: int = 1
     """PROCESS run mode (see `PROCESSRunMode` for descriptions)
     """
 
-    i_figure_merit: int | FiguresOfMerit = 7
+    i_figure_merit: int = 7
     """
     Switch for figure-of-merit (see `FiguresOfMerit` for descriptions)
     negative => maximise, positive => minimise

From d4c35925f1f85b8865278b47924402b929bfb3eb Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Tue, 11 Aug 2026 14:15:28 +0100
Subject: [PATCH 11/13] Rename solver variables to align with style guide

---
 process/core/init.py                          |  6 +-
 process/core/solver/objectives.py             |  4 +-
 .../data/large_tokamak_1_MFILE.DAT            |  6 +-
 .../data/large_tokamak_2_MFILE.DAT            |  6 +-
 .../data/large_tokamak_3_MFILE.DAT            |  6 +-
 .../data/large_tokamak_4_MFILE.DAT            |  6 +-
 tests/integration/data/large_tokamak_IN.DAT   |  2 +-
 .../integration/data/large_tokamak_MFILE.DAT  | 10 +--
 tests/integration/data/ref_IN.DAT             |  4 +-
 tests/integration/data/scan_2D_MFILE.DAT      | 62 +++++++++----------
 tests/integration/data/scan_MFILE.DAT         | 40 ++++++------
 tests/unit/data/large_tokamak_IN.DAT          |  2 +-
 tests/unit/data/large_tokamak_MFILE.DAT       | 10 +--
 13 files changed, 83 insertions(+), 81 deletions(-)

diff --git a/process/core/init.py b/process/core/init.py
index 5ec28d7557..a5c4f7933c 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -184,7 +184,7 @@ def run_summary(data: DataStructure):
         process_output.ocmmnt(
             outfile,
             f"Total constraints : "
-            f"{data.numerics.n_inequality_constraints + data.numerics.n_equality_constraints}",
+            f"{data.numerics.n_inequality_constraints + data.numerics.n_equality_constraints}",  # noqa: E501
         )
         process_output.ocmmnt(
             outfile, f"Iteration variables : {data.numerics.n_iteration_variables}"
@@ -287,7 +287,9 @@ def check_process(inputs, data):  # noqa: ARG001
 
     # Can't use c_tf_turn as iteration var, constraint or
     # input if i_tf_turns_integer == 1
-    if (data.numerics.ixc[: data.numerics.n_iteration_variables] == 60).any() and TFWPIntegerTurnType(
+    if (
+        data.numerics.ixc[: data.numerics.n_iteration_variables] == 60
+    ).any() and TFWPIntegerTurnType(
         data.tfcoil.i_tf_turns_integer
     ) == TFWPIntegerTurnType.INTEGER:
         raise ProcessValidationError(
diff --git a/process/core/solver/objectives.py b/process/core/solver/objectives.py
index e8b369d6e3..71a15b9082 100644
--- a/process/core/solver/objectives.py
+++ b/process/core/solver/objectives.py
@@ -85,8 +85,8 @@ def objective_function(i_figure_merit: int, data: DataStructure) -> float:
             == AvailabilityModel.USER_INPUT
         ):
             raise ProcessValueError(
-                "i_figure_merit=15 requires `f_t_plant_available` to be calculated, not user "
-                "input"
+                "i_figure_merit=15 requires `f_t_plant_available` to be calculated, not "
+                "user input"
             )
         objective_metric = data.costs.f_t_plant_available
     elif figure_of_merit == FiguresOfMerit.MIN_R0_MAX_TAU_BURN:
diff --git a/tests/integration/data/large_tokamak_1_MFILE.DAT b/tests/integration/data/large_tokamak_1_MFILE.DAT
index f1b4616e02..ecb732f076 100644
--- a/tests/integration/data/large_tokamak_1_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_1_MFILE.DAT
@@ -16,8 +16,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.8713E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -1201,7 +1201,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/large_tokamak_2_MFILE.DAT b/tests/integration/data/large_tokamak_2_MFILE.DAT
index a1879daf19..9613cd00e7 100644
--- a/tests/integration/data/large_tokamak_2_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_2_MFILE.DAT
@@ -16,8 +16,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Objective_function_name_________________________________________________ (objf_name)___________________     "major radius"   
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.8713E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
@@ -1202,7 +1202,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/large_tokamak_3_MFILE.DAT b/tests/integration/data/large_tokamak_3_MFILE.DAT
index 8bc333636b..29079d6976 100644
--- a/tests/integration/data/large_tokamak_3_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_3_MFILE.DAT
@@ -16,8 +16,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Objective_function_name_________________________________________________ (objf_name)___________________     "major radius"  
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.8713E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
@@ -1202,7 +1202,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/large_tokamak_4_MFILE.DAT b/tests/integration/data/large_tokamak_4_MFILE.DAT
index 1a79c5e241..293642b7b7 100644
--- a/tests/integration/data/large_tokamak_4_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_4_MFILE.DAT
@@ -16,8 +16,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Objective_function_name_________________________________________________ (objf_name)___________________     "major radius"  
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.8713E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
@@ -1202,7 +1202,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/large_tokamak_IN.DAT b/tests/integration/data/large_tokamak_IN.DAT
index 1bc89e20e7..499984ff10 100644
--- a/tests/integration/data/large_tokamak_IN.DAT
+++ b/tests/integration/data/large_tokamak_IN.DAT
@@ -12,7 +12,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/large_tokamak_MFILE.DAT b/tests/integration/data/large_tokamak_MFILE.DAT
index 780f62eba2..0e8a6c0645 100644
--- a/tests/integration/data/large_tokamak_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_MFILE.DAT
@@ -10,15 +10,15 @@ PROCESS_run_title________________________________________________________ (runti
 PROCESS_git_tag__________________________________________________________ (tagno)________________________ "v3.4.1-57-g7c9ef8f4d" 
 PROCESS_git_branch_______________________________________________________ (branch_name)__________________ "refactor_cs" 
 Input_filename___________________________________________________________ (fileprefix)___________________ "/home/mn3981/PROCESS/tests/integration/data/large_tokamak_IN.DAT" 
-Optimisation_switch______________________________________________________ (ioptimz)______________________            1 
-Figure_of_merit_switch___________________________________________________ (minmax)_______________________            1 
+Optimisation_switch______________________________________________________ (i_process_run_mode)______________________            1 
+Figure_of_merit_switch___________________________________________________ (i_figure_merit)_______________________            1 
 # Numerics #
 # PROCESS found a feasible solution #
 Error_flag_______________________________________________________________ (ifail)________________________            1 
 Number_of_iteration_variables____________________________________________ (nvar)_________________________           19 
 Number_of_constraints_(total)____________________________________________ (neqns+nineqns)________________           26 
-Optimisation_switch______________________________________________________ (ioptimz)______________________            1 
-Figure_of_merit_switch___________________________________________________ (minmax)_______________________            1 
+Optimisation_switch______________________________________________________ (i_process_run_mode)______________________            1 
+Figure_of_merit_switch___________________________________________________ (i_figure_merit)_______________________            1 
 Objective_function_name__________________________________________________ (objf_name)____________________ "Plasma major radius (R₀)" 
 Normalised_objective_function____________________________________________ (norm_objf)____________________ 1.60000000003450937e+00 OP 
 Square_root_of_the_sum_of_squares_of_the_constraint_residuals____________ (sqsumsq)______________________ 1.09745036021651941e-09 OP 
@@ -35916,7 +35916,7 @@ Error_status_____________________________________________________________ (error
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/ref_IN.DAT b/tests/integration/data/ref_IN.DAT
index cc82c1f316..0255d192ed 100644
--- a/tests/integration/data/ref_IN.DAT
+++ b/tests/integration/data/ref_IN.DAT
@@ -195,8 +195,8 @@ f_nd_impurity_electrons(14) = 5e-05
 
 *---------------------Numerics---------------------*
 
-ioptimz  = 1 * for optimisation VMCON only
-minmax   = 1 * Switch for figure-of-merit (see lablmm for descriptions)
+i_process_run_mode  = 1 * for optimisation VMCON only
+i_figure_merit   = 1 * Switch for figure-of-merit (see lablmm for descriptions)
 epsvmc   = 1.0e-8 * Error tolerance for vmcon
 
 *-----------------Pfcoil Variables-----------------*
diff --git a/tests/integration/data/scan_2D_MFILE.DAT b/tests/integration/data/scan_2D_MFILE.DAT
index de279072f9..4e011f5f30 100644
--- a/tests/integration/data/scan_2D_MFILE.DAT
+++ b/tests/integration/data/scan_2D_MFILE.DAT
@@ -24,8 +24,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      4.9491E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -1187,8 +1187,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.2876E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -2350,8 +2350,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      5.5704E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -3513,8 +3513,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.9629E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -4676,8 +4676,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9970E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -5839,8 +5839,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      8.1440E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -7002,8 +7002,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      4.5526E-06 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -8165,8 +8165,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      9.6125E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -9328,8 +9328,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      7.6750E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -10491,8 +10491,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.3614E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -11654,8 +11654,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.0000E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -12817,8 +12817,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      6.7424E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -13980,8 +13980,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.5954E-05 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -15143,8 +15143,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.3866E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -16306,8 +16306,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.4132E-04 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      0.0000E+00 OP 
  Normalised_objective_function___________________________________________ (norm_objf)___________________      1.6000E+00 OP 
@@ -17484,7 +17484,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/integration/data/scan_MFILE.DAT b/tests/integration/data/scan_MFILE.DAT
index 2b573c476a..b02e8d7747 100644
--- a/tests/integration/data/scan_MFILE.DAT
+++ b/tests/integration/data/scan_MFILE.DAT
@@ -18,8 +18,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      8.4149E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      1.4624E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________             68 OP 
@@ -1013,8 +1013,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9283E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.0653E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -2008,8 +2008,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9329E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.0396E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -3003,8 +3003,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9515E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.0186E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -3998,8 +3998,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9861E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.0194E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -4993,8 +4993,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.0397E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.0474E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -5988,8 +5988,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.1174E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.1102E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -6983,8 +6983,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.2269E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.2193E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -7978,8 +7978,8 @@
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
  Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
- Optimisation_switch_____________________________________________________ (ioptimz)_____________________              1    
- Figure_of_merit_switch__________________________________________________ (minmax)______________________              1    
+ Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
+ Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.3800E-09 OP 
  VMCON_convergence_parameter_____________________________________________ (convergence_parameter)_______      5.3917E-09 OP 
  Number_of_VMCON_iterations______________________________________________ (nviter)______________________              5 OP 
@@ -9196,8 +9196,8 @@ fimp(14) = 5e-05
 
 *---------------------Numerics---------------------*
 
-ioptimz  = 1 * for optimisation VMCON only
-minmax   = 1 * Switch for figure-of-merit (see lablmm for descriptions)
+i_process_run_mode  = 1 * for optimisation VMCON only
+i_figure_merit   = 1 * Switch for figure-of-merit (see lablmm for descriptions)
 epsvmc   = 1.0e-8 * Error tolerance for vmcon
 
 *-----------------Pfcoil Variables-----------------*
diff --git a/tests/unit/data/large_tokamak_IN.DAT b/tests/unit/data/large_tokamak_IN.DAT
index 1bc89e20e7..499984ff10 100644
--- a/tests/unit/data/large_tokamak_IN.DAT
+++ b/tests/unit/data/large_tokamak_IN.DAT
@@ -12,7 +12,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
diff --git a/tests/unit/data/large_tokamak_MFILE.DAT b/tests/unit/data/large_tokamak_MFILE.DAT
index 3683214ef7..7cc5206a6e 100644
--- a/tests/unit/data/large_tokamak_MFILE.DAT
+++ b/tests/unit/data/large_tokamak_MFILE.DAT
@@ -10,15 +10,15 @@ PROCESS_run_title________________________________________________________ (runti
 PROCESS_git_tag__________________________________________________________ (tagno)________________________ "v3.2.1-20-g7621ab10" 
 PROCESS_git_branch_______________________________________________________ (branch_name)__________________ "update-tracked-mfiles" 
 Input_filename___________________________________________________________ (fileprefix)___________________ "/home/clair/development/PROCESS/tests/unit/data/large_tokamak_IN.DAT" 
-Optimisation_switch______________________________________________________ (ioptimz)______________________            1 
-Figure_of_merit_switch___________________________________________________ (minmax)_______________________            1 
+Optimisation_switch______________________________________________________ (i_process_run_mode)______________________            1 
+Figure_of_merit_switch___________________________________________________ (i_figure_merit)_______________________            1 
 # Numerics #
 # PROCESS found a feasible solution #
 Error_flag_______________________________________________________________ (ifail)________________________            1 
 Number_of_iteration_variables____________________________________________ (nvar)_________________________           43 
 Number_of_constraints_(total)____________________________________________ (neqns+nineqns)________________           26 
-Optimisation_switch______________________________________________________ (ioptimz)______________________            1 
-Figure_of_merit_switch___________________________________________________ (minmax)_______________________            1 
+Optimisation_switch______________________________________________________ (i_process_run_mode)______________________            1 
+Figure_of_merit_switch___________________________________________________ (i_figure_merit)_______________________            1 
 Objective_function_name__________________________________________________ (objf_name)____________________ "major radius          " 
 Normalised_objective_function____________________________________________ (norm_objf)____________________ 1.60000000000000009e+00 OP 
 Square_root_of_the_sum_of_squares_of_the_constraint_residuals____________ (sqsumsq)______________________ 5.51527684827371492e-08 OP 
@@ -7621,7 +7621,7 @@ Error_status_____________________________________________________________ (error
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7

From 87823e709acb476e40f0e3725d340d287242c77d Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 14 Aug 2026 10:34:00 +0100
Subject: [PATCH 12/13] Post rebase fixes

---
 process/core/caller.py                | 23 ++++++++------
 process/core/solver/constraints.py    | 12 ++++---
 process/core/solver/objectives.py     |  2 +-
 process/core/solver/solver_handler.py | 45 ++++++++++++++++-----------
 4 files changed, 49 insertions(+), 33 deletions(-)

diff --git a/process/core/caller.py b/process/core/caller.py
index 463d041d80..c35a48375e 100644
--- a/process/core/caller.py
+++ b/process/core/caller.py
@@ -419,7 +419,7 @@ def finalise(models, data, ifail: int, non_idempotent_msg: str | None = None):
         po.oheadr(constants.NOUT, "Final UNFEASIBLE Point")
 
     # Output relevant to no optimisation
-    if data.numerics.ioptimz == PROCESSRunMode.EVALUATION:
+    if data.numerics.i_process_run_mode == PROCESSRunMode.EVALUATION:
         output_evaluation(data)
 
     # Print non-idempotence warning to OUT.DAT only
@@ -444,18 +444,23 @@ def output_evaluation(data):
     po.oblnkl(constants.NOUT)
 
     # Evaluate objective function
-    norm_objf = objective_function(data.numerics.minmax, data)
+    norm_objf = objective_function(data.numerics.i_figure_merit, data)
     po.ovarre(constants.MFILE, "Normalised objective function", "(norm_objf)", norm_objf)
 
     # Print the residuals of the constraint equations
 
     residual_error, value, residual, symbols, units = constraints.constraint_eqns(
-        data.numerics.neqns + data.numerics.nineqns, -1, data
+        data.numerics.n_equality_constraints + data.numerics.n_inequality_constraints,
+        -1,
+        data,
     )
 
     labels = [
         data.numerics.lablcc[j - 1]
-        for j in data.numerics.icc[: data.numerics.neqns + data.numerics.nineqns]
+        for j in data.numerics.icc[
+            : data.numerics.n_equality_constraints
+            + data.numerics.n_inequality_constraints
+        ]
     ]
 
     def _fmt(a, units):
@@ -475,7 +480,7 @@ def _fmt(a, units):
         ),
     )
 
-    for i in range(data.numerics.neqns):
+    for i in range(data.numerics.n_equality_constraints):
         constraint_id = data.numerics.icc[i]
         po.ovarre(
             constants.MFILE,
@@ -484,13 +489,13 @@ def _fmt(a, units):
             residual_error[i],
         )
 
-    for i in range(data.numerics.nineqns):
-        constraint_id = data.numerics.icc[data.numerics.neqns + i]
+    for i in range(data.numerics.n_inequality_constraints):
+        constraint_id = data.numerics.icc[data.numerics.n_equality_constraints + i]
         po.ovarre(
             constants.MFILE,
-            f"{labels[data.numerics.neqns + i]}",
+            f"{labels[data.numerics.n_equality_constraints + i]}",
             f"(ineq_con{constraint_id:03d})",
-            residual_error[data.numerics.neqns + i],
+            residual_error[data.numerics.n_equality_constraints + i],
         )
 
 
diff --git a/process/core/solver/constraints.py b/process/core/solver/constraints.py
index c531a28be7..72c11014fd 100644
--- a/process/core/solver/constraints.py
+++ b/process/core/solver/constraints.py
@@ -2022,11 +2022,13 @@ def constraints_output(data: DataStructure, solver_name: str):
         "The following equality constraint residues should be close to zero:",
     )
 
-    con1, con2, err, _, lab = constraint_eqns(nums.neqns + nums.nineqns, -1, data)
+    con1, con2, err, _, lab = constraint_eqns(
+        nums.n_equality_constraints + nums.n_inequality_constraints, -1, data
+    )
 
     # Write equality constraints to mfile
     equality_constraint_table = []
-    for i in range(nums.neqns):
+    for i in range(nums.n_equality_constraints):
         name = nums.lablcc[nums.icc[i] - 1]
 
         equality_constraint_table.append([
@@ -2062,7 +2064,7 @@ def constraints_output(data: DataStructure, solver_name: str):
     )
 
     # Write inequality constraints
-    if nums.nineqns > 0:
+    if nums.n_inequality_constraints > 0:
         inequality_constraint_table = []
         # Inequalities not necessarily satisfied when evaluating
         process_output.osubhd(
@@ -2078,8 +2080,8 @@ def constraints_output(data: DataStructure, solver_name: str):
             )
 
         for i in range(
-            nums.neqns,
-            nums.neqns + nums.nineqns,
+            nums.n_equality_constraints,
+            nums.n_equality_constraints + nums.n_inequality_constraints,
         ):
             name = nums.lablcc[nums.icc[i] - 1]
             constraint = ConstraintManager.evaluate_constraint(int(nums.icc[i]), data)
diff --git a/process/core/solver/objectives.py b/process/core/solver/objectives.py
index 71a15b9082..bd99f5664c 100644
--- a/process/core/solver/objectives.py
+++ b/process/core/solver/objectives.py
@@ -40,7 +40,7 @@ def objective_function(i_figure_merit: int, data: DataStructure) -> float:
     Raises
     ------
     ProcessValueError
-        If minmax=15 not used with i_plant_availability=1
+        If i_figure_merit=15 not used with i_plant_availability=1
     """
     try:
         figure_of_merit = FiguresOfMerit(abs(i_figure_merit))
diff --git a/process/core/solver/solver_handler.py b/process/core/solver/solver_handler.py
index d731a11c95..5009203f44 100644
--- a/process/core/solver/solver_handler.py
+++ b/process/core/solver/solver_handler.py
@@ -51,9 +51,13 @@ def run(self):
         # Initialise iteration variables and bounds in Python: relies on Fortran
         # iteration variables being defined above
         # Trim maximum size arrays down to actually used size
-        x = self.data.numerics.xcm[: self.data.numerics.nvar]
-        bndl = self.data.numerics.itv_scaled_lower_bounds[: self.data.numerics.nvar]
-        bndu = self.data.numerics.itv_scaled_upper_bounds[: self.data.numerics.nvar]
+        x = self.data.numerics.xcm[: self.data.numerics.n_iteration_variables]
+        bndl = self.data.numerics.itv_scaled_lower_bounds[
+            : self.data.numerics.n_iteration_variables
+        ]
+        bndu = self.data.numerics.itv_scaled_upper_bounds[
+            : self.data.numerics.n_iteration_variables
+        ]
 
         # Evaluators() calculates the objective and constraint functions and
         # their gradients for a given vector x
@@ -66,8 +70,9 @@ def run(self):
         self.solver.set_opt_params(x)
         # Define total number of constraints and equality constraints
         self.solver.set_constraints(
-            m=self.data.numerics.neqns + self.data.numerics.nineqns,
-            meq=self.data.numerics.neqns,
+            m=self.data.numerics.n_equality_constraints
+            + self.data.numerics.n_inequality_constraints,
+            meq=self.data.numerics.n_equality_constraints,
         )
         ifail = self.solver.solve()
 
@@ -116,7 +121,7 @@ def output(self):
     def _numerics_output(self):
         nums = self.data.numerics
 
-        nums.sqsumsq = sum(r**2 for r in nums.rcm[: nums.neqns]) ** 0.5
+        nums.sqsumsq = sum(r**2 for r in nums.rcm[: nums.n_equality_constraints]) ** 0.5
 
         process_output.oheadr(constants.NOUT, "Numerics")
         s_type = (
@@ -163,19 +168,23 @@ def _numerics_output(self):
                 logger.warning(f"High final constraint residues. {nums.sqsumsq=}")
 
         for d, var, v in (
-            ("Number of iteration variables", "(nvar)", nums.nvar),
+            (
+                "Number of iteration variables",
+                "(n_iteration_variables)",
+                nums.n_iteration_variables,
+            ),
             (
                 "Number of constraints (total)",
-                "(neqns+nineqns)",
-                nums.neqns + nums.nineqns,
+                "(n_equality_constraints+n_inequality_constraints)",
+                nums.n_equality_constraints + nums.n_inequality_constraints,
             ),
-            ("Optimisation switch", "(ioptimz)", nums.ioptimz),
+            ("Optimisation switch", "(i_process_run_mode)", nums.i_process_run_mode),
         ):
             process_output.ovarre(constants.NOUT, d, var, v)
 
         process_output.ocmmnt(
             constants.NOUT,
-            f"     {PROCESSRunMode(nums.ioptimz).description}",
+            f"     {PROCESSRunMode(nums.i_process_run_mode).description}",
         )
 
         # Objective function output: none for fsolve
@@ -183,11 +192,11 @@ def _numerics_output(self):
             process_output.ovarre(
                 constants.NOUT,
                 "Figure of merit switch",
-                "(minmax)",
-                nums.minmax,
+                "(i_figure_merit)",
+                nums.i_figure_merit,
             )
 
-            nums.objf_name = f'"{FiguresOfMerit(abs(nums.minmax)).description}"'
+            nums.objf_name = f'"{FiguresOfMerit(abs(nums.i_figure_merit)).description}"'
 
             for d, var, v, o in (
                 ("Objective function name", "(objf_name)", nums.objf_name, ""),
@@ -200,8 +209,8 @@ def _numerics_output(self):
                 ),
                 (
                     "Number of optimising solver iterations",
-                    "(nviter)",
-                    nums.nviter,
+                    "(n_solver_iterations)",
+                    nums.n_solver_iterations,
                     "OP ",
                 ),
             ):
@@ -234,7 +243,7 @@ def _numerics_output(self):
                         else "PROCESS has failed to optimise"
                     )
                     + " the optimisation parameters to"
-                    + ("minimise" if nums.minmax > 0 else "maximise")
+                    + ("minimise" if nums.i_figure_merit > 0 else "maximise")
                     + f" the objective function: {nums.objf_name}\n"
                 ),
             )
@@ -246,7 +255,7 @@ def _optimisation_parameters_output(self):
 
         # Output optimisation parameters
         solution_vector_table = []
-        for i in range(nums.nvar):
+        for i in range(nums.n_iteration_variables):
             nums.xcs[i] = nums.xcm[i] * nums.scafc[i]
 
             name = nums.lablxc[nums.ixc[i] - 1]

From 169beb718e157d5c55078890c16c90b285f00b73 Mon Sep 17 00:00:00 2001
From: mn3981 <christopher.ashe@ukaea.uk>
Date: Fri, 14 Aug 2026 11:04:18 +0100
Subject: [PATCH 13/13] Rename solver variables to align with style guide

---
 examples/data/large_tokamak_IN.DAT            |  4 +--
 examples/data/scan_example_file_IN.DAT        |  4 +--
 process/core/init.py                          | 16 +++++-----
 process/core/io/plot/summary.py               | 12 ++++----
 .../data/large_tokamak_1_MFILE.DAT            |  2 +-
 .../data/large_tokamak_2_MFILE.DAT            |  2 +-
 .../data/large_tokamak_3_MFILE.DAT            |  2 +-
 .../data/large_tokamak_4_MFILE.DAT            |  2 +-
 tests/integration/data/large_tokamak_IN.DAT   |  2 +-
 .../integration/data/large_tokamak_MFILE.DAT  |  4 +--
 tests/integration/data/scan_2D_MFILE.DAT      | 30 +++++++++----------
 tests/integration/data/scan_MFILE.DAT         | 18 +++++------
 tests/regression/input_files/IFE.IN.DAT       |  2 +-
 tests/unit/core/test_input.py                 |  5 +++-
 tests/unit/data/large_tokamak_IN.DAT          |  2 +-
 tests/unit/data/large_tokamak_MFILE.DAT       |  2 +-
 16 files changed, 57 insertions(+), 52 deletions(-)

diff --git a/examples/data/large_tokamak_IN.DAT b/examples/data/large_tokamak_IN.DAT
index 33ca94ec74..38f47a3088 100644
--- a/examples/data/large_tokamak_IN.DAT
+++ b/examples/data/large_tokamak_IN.DAT
@@ -12,12 +12,12 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
 
-neqns = 3
+n_equality_constraints = 3
 
 * Constraint Equations - Consistency Equations *
 ************************************************
diff --git a/examples/data/scan_example_file_IN.DAT b/examples/data/scan_example_file_IN.DAT
index e34e1708c3..98ddfa091d 100644
--- a/examples/data/scan_example_file_IN.DAT
+++ b/examples/data/scan_example_file_IN.DAT
@@ -12,7 +12,7 @@
 runtitle = Generic large tokamak
 
 * Figure of merit - minimise major radius
-minmax = 1
+i_figure_merit = 1
 
 * Error tolerance for VMCON
 epsvmc = 1e-7
@@ -20,7 +20,7 @@ epsvmc = 1e-7
 * Inequality constraint tolerance 
 force_vmcon_inequality_tolerance = 1e-6
 
-neqns = 3
+n_equality_constraints = 3
 
 * Scan Variables *
 ******************
diff --git a/process/core/init.py b/process/core/init.py
index a5c4f7933c..7704fd05e8 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -197,17 +197,18 @@ def run_summary(data: DataStructure):
             )
 
             if data.numerics.i_figure_merit > 0:
-                minmax_string = "  -- minimise "
-                minmax_sign = "+"
+                figure_merit_string = "  -- minimise "
+                figure_merit_sign = "+"
             else:
-                minmax_string = "  -- maximise "
-                minmax_sign = "-"
+                figure_merit_string = "  -- maximise "
+                figure_merit_sign = "-"
 
             fom_string = FiguresOfMerit(abs(data.numerics.i_figure_merit)).description
             process_output.ocmmnt(
                 outfile,
-                f"Figure of merit : {minmax_sign}{abs(data.numerics.i_figure_merit)}"
-                f"{minmax_string}{fom_string}",
+                f"Figure of merit : "
+                f"{figure_merit_sign}{abs(data.numerics.i_figure_merit)}"
+                f"{figure_merit_string}{fom_string}",
             )
             process_output.ocmmnt(
                 outfile,
@@ -263,7 +264,8 @@ def check_process(inputs, data):  # noqa: ARG001
     # Check that there are sufficient iteration variables
     if data.numerics.n_iteration_variables < data.numerics.n_equality_constraints:
         raise ProcessValidationError(
-            "Insufficient iteration variables to solve the problem! NVAR < NEQNS",
+            "Insufficient iteration variables to solve the problem! "
+            "n_iteration_variables < n_equality_constraints",
             n_iteration_variables=data.numerics.n_iteration_variables,
             n_equality_constraints=data.numerics.n_equality_constraints,
         )
diff --git a/process/core/io/plot/summary.py b/process/core/io/plot/summary.py
index d87c486c88..5c53ac2933 100644
--- a/process/core/io/plot/summary.py
+++ b/process/core/io/plot/summary.py
@@ -12075,7 +12075,7 @@ def plot_cover_page(
     branch_name = mfile.get("branch_name", scan=-1)
     fileprefix = mfile.get("fileprefix", scan=-1)
     optmisation_switch = int(mfile.get("i_process_run_mode", scan=-1))
-    minmax_switch = mfile.get("i_figure_merit", scan=-1) or "N/A"
+    figure_merit_switch = mfile.get("i_figure_merit", scan=-1) or "N/A"
     ifail = mfile.get("ifail", scan=-1)
     nvars = mfile.get("n_iteration_variables", scan=-1)
     # Objective_function_name
@@ -12088,13 +12088,13 @@ def plot_cover_page(
     n_solver_iterations = int(mfile.get("n_solver_iterations", scan=-1)) or "N/A"
 
     # Objective name with minimising/maximising
-    if isinstance(minmax_switch, str):
+    if isinstance(figure_merit_switch, str):
         objective_text = ""
-    elif minmax_switch >= 0:
-        minmax_switch = int(minmax_switch)
+    elif figure_merit_switch >= 0:
+        figure_merit_switch = int(figure_merit_switch)
         objective_text = f"  -> Minimising: {objf_name}"
     else:
-        minmax_switch = int(minmax_switch)
+        figure_merit_switch = int(figure_merit_switch)
         objective_text = f"  -> Maximising: {objf_name}"
 
     axis.text(
@@ -12157,7 +12157,7 @@ def plot_cover_page(
     settings_info = (
         f"• Optimisation Switch: {int(optmisation_switch)}\n"
         f"     {PROCESSRunMode(int(optmisation_switch)).description}\n"
-        f"• Figure of Merit Switch (i_figure_merit): {minmax_switch}\n"
+        f"• Figure of Merit Switch (i_figure_merit): {figure_merit_switch}\n"
         f"     {objective_text}\n"
         f"• Fail Status (ifail): {int(ifail)}\n"
         f"• Number of Iteration Variables: {int(nvars)}\n"
diff --git a/tests/integration/data/large_tokamak_1_MFILE.DAT b/tests/integration/data/large_tokamak_1_MFILE.DAT
index ecb732f076..0ba36d9cd5 100644
--- a/tests/integration/data/large_tokamak_1_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_1_MFILE.DAT
@@ -15,7 +15,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.8713E-04 OP 
diff --git a/tests/integration/data/large_tokamak_2_MFILE.DAT b/tests/integration/data/large_tokamak_2_MFILE.DAT
index 9613cd00e7..640640c6b0 100644
--- a/tests/integration/data/large_tokamak_2_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_2_MFILE.DAT
@@ -15,7 +15,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Objective_function_name_________________________________________________ (objf_name)___________________     "major radius"   
diff --git a/tests/integration/data/large_tokamak_3_MFILE.DAT b/tests/integration/data/large_tokamak_3_MFILE.DAT
index 29079d6976..2c49f31188 100644
--- a/tests/integration/data/large_tokamak_3_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_3_MFILE.DAT
@@ -15,7 +15,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Objective_function_name_________________________________________________ (objf_name)___________________     "major radius"  
diff --git a/tests/integration/data/large_tokamak_4_MFILE.DAT b/tests/integration/data/large_tokamak_4_MFILE.DAT
index 293642b7b7..9748b8980c 100644
--- a/tests/integration/data/large_tokamak_4_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_4_MFILE.DAT
@@ -15,7 +15,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             45    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Objective_function_name_________________________________________________ (objf_name)___________________     "major radius"  
diff --git a/tests/integration/data/large_tokamak_IN.DAT b/tests/integration/data/large_tokamak_IN.DAT
index 499984ff10..e8786bb04b 100644
--- a/tests/integration/data/large_tokamak_IN.DAT
+++ b/tests/integration/data/large_tokamak_IN.DAT
@@ -17,7 +17,7 @@ i_figure_merit = 1
 * Error tolerance for VMCON
 epsvmc = 1e-7
 
-neqns = 3
+n_equality_constraints = 3
 
 * Constraint Equations - Consistency Equations *
 ************************************************
diff --git a/tests/integration/data/large_tokamak_MFILE.DAT b/tests/integration/data/large_tokamak_MFILE.DAT
index 0e8a6c0645..0d3c8820ff 100644
--- a/tests/integration/data/large_tokamak_MFILE.DAT
+++ b/tests/integration/data/large_tokamak_MFILE.DAT
@@ -16,7 +16,7 @@ Figure_of_merit_switch___________________________________________________ (i_fig
 # PROCESS found a feasible solution #
 Error_flag_______________________________________________________________ (ifail)________________________            1 
 Number_of_iteration_variables____________________________________________ (nvar)_________________________           19 
-Number_of_constraints_(total)____________________________________________ (neqns+nineqns)________________           26 
+Number_of_constraints_(total)____________________________________________ (n_equality_constraints+nineqns)________________           26 
 Optimisation_switch______________________________________________________ (i_process_run_mode)______________________            1 
 Figure_of_merit_switch___________________________________________________ (i_figure_merit)_______________________            1 
 Objective_function_name__________________________________________________ (objf_name)____________________ "Plasma major radius (R₀)" 
@@ -35921,7 +35921,7 @@ i_figure_merit = 1
 * Error tolerance for VMCON
 epsvmc = 1e-7
 
-neqns = 3
+n_equality_constraints = 3
 
 * Constraint Equations - Consistency Equations *
 ************************************************
diff --git a/tests/integration/data/scan_2D_MFILE.DAT b/tests/integration/data/scan_2D_MFILE.DAT
index 4e011f5f30..6ebf98ee83 100644
--- a/tests/integration/data/scan_2D_MFILE.DAT
+++ b/tests/integration/data/scan_2D_MFILE.DAT
@@ -23,7 +23,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      4.9491E-05 OP 
@@ -1186,7 +1186,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.2876E-04 OP 
@@ -2349,7 +2349,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      5.5704E-05 OP 
@@ -3512,7 +3512,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.9629E-05 OP 
@@ -4675,7 +4675,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9970E-04 OP 
@@ -5838,7 +5838,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      8.1440E-05 OP 
@@ -7001,7 +7001,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      4.5526E-06 OP 
@@ -8164,7 +8164,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      9.6125E-05 OP 
@@ -9327,7 +9327,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      7.6750E-05 OP 
@@ -10490,7 +10490,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.3614E-05 OP 
@@ -11653,7 +11653,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.0000E-04 OP 
@@ -12816,7 +12816,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      6.7424E-05 OP 
@@ -13979,7 +13979,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.5954E-05 OP 
@@ -15142,7 +15142,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.3866E-04 OP 
@@ -16305,7 +16305,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             43    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             26    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             26    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      1.4132E-04 OP 
diff --git a/tests/integration/data/scan_MFILE.DAT b/tests/integration/data/scan_MFILE.DAT
index b02e8d7747..0258654bd3 100644
--- a/tests/integration/data/scan_MFILE.DAT
+++ b/tests/integration/data/scan_MFILE.DAT
@@ -17,7 +17,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      8.4149E-09 OP 
@@ -1012,7 +1012,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9283E-09 OP 
@@ -2007,7 +2007,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9329E-09 OP 
@@ -3002,7 +3002,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9515E-09 OP 
@@ -3997,7 +3997,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      2.9861E-09 OP 
@@ -4992,7 +4992,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.0397E-09 OP 
@@ -5987,7 +5987,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.1174E-09 OP 
@@ -6982,7 +6982,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.2269E-09 OP 
@@ -7977,7 +7977,7 @@
  VMCON_error_flag________________________________________________________ (ifail)_______________________              1    
  # PROCESS found a feasible solution #
  Number_of_iteration_variables___________________________________________ (nvar)________________________             40    
- Number_of_constraints_(total)___________________________________________ (neqns+nineqns)_______________             24    
+ Number_of_constraints_(total)___________________________________________ (n_equality_constraints+nineqns)_______________             24    
  Optimisation_switch_____________________________________________________ (i_process_run_mode)_____________________              1    
  Figure_of_merit_switch__________________________________________________ (i_figure_merit)______________________              1    
  Square_root_of_the_sum_of_squares_of_the_constraint_residuals___________ (sqsumsq)_____________________      3.3800E-09 OP 
diff --git a/tests/regression/input_files/IFE.IN.DAT b/tests/regression/input_files/IFE.IN.DAT
index ba668e69f3..68f2fd30df 100644
--- a/tests/regression/input_files/IFE.IN.DAT
+++ b/tests/regression/input_files/IFE.IN.DAT
@@ -23,7 +23,7 @@ runtitle = IFE_001
 p_plant_electric_net_required_mw  = 1000.0     *Required net electric power (MW)
 
 *---------------Numerics Variables-----------------*
-IOPTIMZ   = 1         *Code operation switch (1: for optimisation VMCON only)
+i_process_run_mode   = 1         *Code operation switch (1: for optimisation VMCON only)
 i_figure_merit    = 18        *Null FoM, find feasible
 maxcal    = 100       *Maximum number of solver iterations
 
diff --git a/tests/unit/core/test_input.py b/tests/unit/core/test_input.py
index 6175e19481..b716e7a170 100644
--- a/tests/unit/core/test_input.py
+++ b/tests/unit/core/test_input.py
@@ -102,7 +102,10 @@ def test_exact_parsing(value, tmp_path, data_structure_obj):
 def test_parse_input(tmp_path, data_structure_obj):
     data_structure_obj.globals.fileprefix = _create_input_file(
         tmp_path,
-        ("runtitle = my run title\nioptimz = -2\nepsvmc = 0.6\nboundl(1) = 0.5"),
+        (
+            "runtitle = my run title\ni_process_run_mode = -2\nepsvmc = 0.6\nboundl(1) "
+            "= 0.5"
+        ),
     )
     init.init_process(data_structure_obj)
 
diff --git a/tests/unit/data/large_tokamak_IN.DAT b/tests/unit/data/large_tokamak_IN.DAT
index 499984ff10..e8786bb04b 100644
--- a/tests/unit/data/large_tokamak_IN.DAT
+++ b/tests/unit/data/large_tokamak_IN.DAT
@@ -17,7 +17,7 @@ i_figure_merit = 1
 * Error tolerance for VMCON
 epsvmc = 1e-7
 
-neqns = 3
+n_equality_constraints = 3
 
 * Constraint Equations - Consistency Equations *
 ************************************************
diff --git a/tests/unit/data/large_tokamak_MFILE.DAT b/tests/unit/data/large_tokamak_MFILE.DAT
index 7cc5206a6e..4fbc61943a 100644
--- a/tests/unit/data/large_tokamak_MFILE.DAT
+++ b/tests/unit/data/large_tokamak_MFILE.DAT
@@ -16,7 +16,7 @@ Figure_of_merit_switch___________________________________________________ (i_fig
 # PROCESS found a feasible solution #
 Error_flag_______________________________________________________________ (ifail)________________________            1 
 Number_of_iteration_variables____________________________________________ (nvar)_________________________           43 
-Number_of_constraints_(total)____________________________________________ (neqns+nineqns)________________           26 
+Number_of_constraints_(total)____________________________________________ (n_equality_constraints+nineqns)________________           26 
 Optimisation_switch______________________________________________________ (i_process_run_mode)______________________            1 
 Figure_of_merit_switch___________________________________________________ (i_figure_merit)_______________________            1 
 Objective_function_name__________________________________________________ (objf_name)____________________ "major radius          "