Add unroll and constructor for SymmetricTensor

include/aspect/utilities.h

@@ -1245,6 +1245,36 @@ namespace aspect
      */
     namespace Tensors
     {
+      /**
+       * Convert a vector of doubles to a SymmetricTensor of the same size.
+       */
+      template <int dim>
+      inline
+      SymmetricTensor<2,dim>
+      to_symmetric_tensor(const ArrayView<double> &values)
+      {
+        // Assemble stress tensor if elastic behavior is enabled
+        SymmetricTensor<2,dim> output;
+        for (unsigned int i=0; i < SymmetricTensor<2,dim>::n_independent_components; ++i)
+          output[SymmetricTensor<2,dim>::unrolled_to_component_indices(i)] = values[i];
+
+        return output;
+      };
+
+
+
+            /**
+       * Convert a vector of doubles to a SymmetricTensor of the same size.
+       */
+      template <int dim>
+      inline
+      void
+      unroll(const SymmetricTensor<2,dim> &tensor,
+             const ArrayView<double> &values)
+      {
+        for (unsigned int i=0; i < SymmetricTensor<2,dim>::n_independent_components; ++i)
+          values[i] = tensor[SymmetricTensor<2,dim>::unrolled_to_component_indices(i)];
+      };
 
       /**
        * Rotate a 3D 4th order tensor representing the full stiffnexx matrix using a 3D 2nd order rotation tensor