add template for separate number of dofs

elements/src/include/ae108/elements/CoreElement.h

@@ -37,6 +37,7 @@ class CoreElement final
     : public ElementBase<CoreElement<MaterialModel_, Integrator_>,
                          typename Integrator_::size_type,
                          typename Integrator_::value_type, Integrator_::size(),
+                         MaterialModel_::degrees_of_freedom(),
                          MaterialModel_::dimension()> {
 public:
   using MaterialModel = MaterialModel_;
@@ -170,16 +171,15 @@ private:
   using TangentSlice = typename std::enable_if<
       Element::degrees_of_freedom() == 0 ||
           sizeof(typename Element::MaterialModel::TangentMatrix) ==
-              Element::degrees_of_freedom() * Element::degrees_of_freedom() *
-                  Element::degrees_of_freedom() *
-                  Element::degrees_of_freedom() *
+              Element::degrees_of_freedom() * Element::dimension() *
+                  Element::degrees_of_freedom() * Element::dimension() *
                   sizeof(typename Element::MaterialModel::value_type),
       Eigen::Map<
           const Eigen::Matrix<typename Element::MaterialModel::value_type,
-                              Element::degrees_of_freedom(),
-                              Element::degrees_of_freedom(), Eigen::RowMajor>,
+                              Element::dimension(), Element::dimension(),
+                              Eigen::RowMajor>,
           0,
-          Eigen::Stride<Eigen::Index{Element::degrees_of_freedom() *
+          Eigen::Stride<Eigen::Index{Element::dimension() *
                                      Element::degrees_of_freedom()},
                         Eigen::Index{1}>>>::type;
 };

elements/src/include/ae108/elements/ElementBase.h

@@ -25,7 +25,7 @@ namespace ae108 {
 namespace elements {
 
 template <class Derived_, class SizeType_, class ValueType_, SizeType_ Size_,
-          SizeType_ DegreesOfFreedom_>
+          SizeType_ DegreesOfFreedom_, SizeType_ Dimension_ = DegreesOfFreedom_>
 struct ElementBase {
   using size_type = SizeType_;
   using value_type = ValueType_;
@@ -67,6 +67,11 @@ struct ElementBase {
     return DegreesOfFreedom_;
   }
 
+  /**
+   * @brief The dimension of physical space.
+   */
+  static constexpr size_type dimension() noexcept { return Dimension_; }
+
   /**
    * @brief Computes the energy for the given displacements.
    * @remark Delegates to the corresponding free function.