[PL] Extract parsing of initial stress.

Adding a new function for parameter lookup of optional tags.

ParameterLib/Utils.h

@@ -142,4 +142,38 @@ Parameter<ParameterDataType>& findParameter(
     return findParameter<ParameterDataType>(name, parameters, num_components,
                                             mesh);
 }
+
+/// Find a parameter of specific type for a name given in the process
+/// configuration under the optional tag.
+/// If the tag is not present, a nullptr will be returned.
+/// The parameter must have the specified number of components.
+/// In the process config a parameter is referenced by a name. For example it
+/// will be looking for a parameter named "K" in the list of parameters
+/// when the tag is "hydraulic_conductivity":
+/// \code
+///     <process>
+///         ...
+///         <hydraulic_conductivity>K</hydraulic_conductivity>
+///     </process>
+/// \endcode
+/// and return a pointer to that parameter. Additionally it checks for the
+/// type of the found parameter.
+template <typename ParameterDataType>
+Parameter<ParameterDataType>* findOptionalTagParameter(
+    BaseLib::ConfigTree const& process_config, std::string const& tag,
+    std::vector<std::unique_ptr<ParameterBase>> const& parameters,
+    int const num_components, MeshLib::Mesh const* const mesh = nullptr)
+{
+    // Find parameter name in process config.
+    auto const name =
+        //! \ogs_file_special
+        process_config.getConfigParameterOptional<std::string>(tag);
+
+    if (!name)
+    {
+        return nullptr;
+    }
+    return &findParameter<ParameterDataType>(*name, parameters, num_components,
+                                             mesh);
+}
 }  // namespace ParameterLib

ProcessLib/SmallDeformation/CreateSmallDeformationProcess.cpp

@@ -12,7 +12,6 @@
 #include <cassert>
 
 #include "MaterialLib/SolidModels/CreateConstitutiveRelation.h"
-#include "MathLib/KelvinVector.h"
 #include "ParameterLib/Utils.h"
 #include "ProcessLib/Output/CreateSecondaryVariables.h"
 #include "ProcessLib/Utils/ProcessUtils.h"
@@ -104,24 +103,12 @@ std::unique_ptr<Process> createSmallDeformationProcess(
             "reference_temperature", std::numeric_limits<double>::quiet_NaN());
 
     // Initial stress conditions
-    ParameterLib::Parameter<double> const* initial_stress = nullptr;
-    auto const initial_stress_parameter_name =
-        //! \ogs_file_param{prj__processes__process__SMALL_DEFORMATION__initial_stress}
-        config.getConfigParameterOptional<std::string>("initial_stress");
-    if (initial_stress_parameter_name)
-    {
-        initial_stress = ParameterLib::findParameterOptional<double>(
-            *initial_stress_parameter_name, parameters,
-            // Symmetric tensor size, 4 or 6, not a Kelvin vector.
-            MathLib::KelvinVector::KelvinVectorDimensions<
-                DisplacementDim>::value,
-            &mesh);
-    }
-    if (initial_stress != nullptr)
-    {
-        DBUG("Use '%s' as initial stress parameter.",
-             initial_stress->name.c_str());
-    }
+    auto const initial_stress = ParameterLib::findOptionalTagParameter<double>(
+        //! \ogs_file_param_special{prj__processes__process__SMALL_DEFORMATION__initial_stress}
+        config, "initial_stress", parameters,
+        // Symmetric tensor size, 4 or 6, not a Kelvin vector.
+        MathLib::KelvinVector::KelvinVectorDimensions<DisplacementDim>::value,
+        &mesh);
 
     SmallDeformationProcessData<DisplacementDim> process_data{
         materialIDs(mesh),   std::move(solid_constitutive_relations),

ProcessLib/ThermoMechanics/CreateThermoMechanicsProcess.cpp

@@ -168,24 +168,12 @@ std::unique_ptr<Process> createThermoMechanicsProcess(
     }
 
     // Initial stress conditions
-    ParameterLib::Parameter<double> const* initial_stress = nullptr;
-    auto const initial_stress_parameter_name =
-        //! \ogs_file_param{prj__processes__process__THERMO_MECHANICS__initial_stress}
-        config.getConfigParameterOptional<std::string>("initial_stress");
-    if (initial_stress_parameter_name)
-    {
-        initial_stress = ParameterLib::findParameterOptional<double>(
-            *initial_stress_parameter_name, parameters,
-            // Symmetric tensor size, 4 or 6, not a Kelvin vector.
-            MathLib::KelvinVector::KelvinVectorDimensions<
-                DisplacementDim>::value,
-            &mesh);
-    }
-    if (initial_stress != nullptr)
-    {
-        DBUG("Use '%s' as initial stress parameter.",
-             initial_stress->name.c_str());
-    }
+    auto const initial_stress = ParameterLib::findOptionalTagParameter<double>(
+        //! \ogs_file_param_special{prj__processes__process__THERMO_MECHANICS__initial_stress}
+        config, "initial_stress", parameters,
+        // Symmetric tensor size, 4 or 6, not a Kelvin vector.
+        MathLib::KelvinVector::KelvinVectorDimensions<DisplacementDim>::value,
+        &mesh);
 
     ThermoMechanicsProcessData<DisplacementDim> process_data{
         materialIDs(mesh),