[M/Bbar] using std::optional as the return type

of the function to comput B_dil_bar matrix, and some other minor changes

ProcessLib/Deformation/LinearBMatrix.h

@@ -12,6 +12,7 @@
 
 #include <Eigen/Core>
 #include <cmath>
+#include <optional>
 
 #include "MeshLib/Elements/Elements.h"
 #include "NumLib/Fem/Integration/GenericIntegrationMethod.h"
@@ -140,7 +141,7 @@ template <int DisplacementDim, int NPOINTS, typename BBarMatrixType,
 void applyBbar(BBarMatrixType const& B_bar, BMatrixType& B,
                const bool is_axially_symmetric)
 {
-    if (DisplacementDim == 3)
+    if constexpr (DisplacementDim == 3)
     {
         for (int i = 0; i < NPOINTS; ++i)
         {
@@ -163,6 +164,7 @@ void applyBbar(BBarMatrixType const& B_bar, BMatrixType& B,
         return;
     }
 
+    // 2D or axisymmetry
     for (int i = 0; i < NPOINTS; ++i)
     {
         auto B_i_0 = B.col(i);
@@ -186,22 +188,23 @@ void applyBbar(BBarMatrixType const& B_bar, BMatrixType& B,
 /// Fills a B matrix, or a B bar matrix if required.
 template <int DisplacementDim, int NPOINTS, typename BBarMatrixType,
           typename BMatrixType, typename N_Type, typename DNDX_Type>
-BMatrixType computeBMatrixPossiblyWithBbar(DNDX_Type const& dNdx,
-                                           N_Type const& N,
-                                           BBarMatrixType const& B_dil_bar,
-                                           const double radius,
-                                           const bool is_axially_symmetric,
-                                           const bool use_b_bar)
+BMatrixType computeBMatrixPossiblyWithBbar(
+    DNDX_Type const& dNdx,
+    N_Type const& N,
+    std::optional<BBarMatrixType> const& B_dil_bar,
+    const double radius,
+    const bool is_axially_symmetric)
 {
     auto B = computeBMatrix<DisplacementDim, NPOINTS, BMatrixType, N_Type,
                             DNDX_Type>(dNdx, N, radius, is_axially_symmetric);
-    if (!use_b_bar)
+
+    if (!B_dil_bar)
     {
         return B;
     }
 
     detail::applyBbar<DisplacementDim, NPOINTS, BBarMatrixType, BMatrixType>(
-        B_dil_bar, B, is_axially_symmetric);
+        *B_dil_bar, B, is_axially_symmetric);
 
     return B;
 }

ProcessLib/SmallDeformation/SmallDeformationFEM.h

@@ -12,6 +12,7 @@
 
 #include <limits>
 #include <memory>
+#include <optional>
 #include <vector>
 
 #include "LocalAssemblerInterface.h"
@@ -211,11 +212,11 @@ public:
             "implemented.");
     }
 
-    BBarMatrixType getDilatationalBBarMatrix() const
+    std::optional<BBarMatrixType> getDilatationalBBarMatrix() const
     {
         if (!(this->process_data_.use_b_bar))
         {
-            return {};
+            return std::nullopt;
         }
 
         return LinearBMatrix::computeDilatationalBbar<
@@ -271,8 +272,7 @@ public:
             auto const B = LinearBMatrix::computeBMatrixPossiblyWithBbar<
                 DisplacementDim, ShapeFunction::NPOINTS, BBarMatrixType,
                 typename BMatricesType::BMatrixType>(
-                dNdx, N, B_dil_bar, x_coord, this->is_axially_symmetric_,
-                this->process_data_.use_b_bar);
+                dNdx, N, B_dil_bar, x_coord, this->is_axially_symmetric_);
 
             auto const CD = updateConstitutiveRelations(
                 B, u, u_prev, x_position, t, dt, constitutive_setting, medium,
@@ -321,8 +321,7 @@ public:
             auto const B = LinearBMatrix::computeBMatrixPossiblyWithBbar<
                 DisplacementDim, ShapeFunction::NPOINTS, BBarMatrixType,
                 typename BMatricesType::BMatrixType>(
-                dNdx, N, B_dil_bar, x_coord, this->is_axially_symmetric_,
-                this->process_data_.use_b_bar);
+                dNdx, N, B_dil_bar, x_coord, this->is_axially_symmetric_);
 
             updateConstitutiveRelations(
                 B, local_x, local_x_prev, x_position, t, dt,