method to compute the actual Hesse matrix. For some strange reason this slows...

method to compute the actual Hesse matrix.  For some strange reason this slows down convergence, rather than speeding it up.  to be investigated

[[Imported from SVN: r7173]]

dune/gfe/averagedistanceassembler.hh

@@ -73,6 +73,25 @@ public:
             matrix.axpy(weights_[i], TargetSpace::secondDerivativeOfDistanceSquaredWRTSecondArgument(coefficients_[i], x));
     }
 
+    void assembleHessian(const TargetSpace& x,
+                         Dune::FieldMatrix<double,size,size>& matrix) const
+    {
+        Dune::FieldMatrix<double,embeddedSize,embeddedSize> embeddedHessian;
+        assembleEmbeddedHessian(x,embeddedHessian);
+        
+        Dune::FieldMatrix<double,size,embeddedSize> frame = x.orthonormalFrame();
+        
+        // this is frame * embeddedHessian * frame^T
+        for (int i=0; i<size; i++)
+            for (int j=0; j<size; j++) {
+                matrix[i][j] = 0;
+                for (int k=0; k<embeddedSize; k++)
+                    for (int l=0; l<embeddedSize; l++)
+                        matrix[i][j] += frame[i][k]*embeddedHessian[k][l]*frame[j][l];
+            }
+        
+    }
+
     const std::vector<TargetSpace> coefficients_;
 
     const std::vector<double> weights_;