Hand-optimize a case in the hot path of the symmetric_gradient function.

git-svn-id: https://svn.dealii.org/trunk@17931 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/deal.II/include/fe/fe_values.h b/deal.II/deal.II/include/fe/fe_values.h
index 71955d37c29548204420c99636cd07346deeee4b..a7f45fb9f1709658e90eea506173034eee4fc801 100644 (file)
--- a/deal.II/deal.II/include/fe/fe_values.h
+++ b/deal.II/deal.II/include/fe/fe_values.h
@@ -3851,6 +3851,85 @@ namespace FEValuesViews
   }
 
 
+  namespace
+  {
+                                    /**
+                                     * Return the symmetrized version of a
+                                     * tensor whose n'th row equals the
+                                     * second argument, with all other rows
+                                     * equal to zero.
+                                     */
+    inline
+    SymmetricTensor<2,1>
+    symmetrize_single_row (const unsigned int n,
+                          const Tensor<1,1> &t)
+    {
+      const unsigned int dim = 1;
+      Assert (n < dim, ExcIndexRange (n, 0, dim));
+      
+      const double array[1] = { t[0] };
+      return SymmetricTensor<2,1>(array);
+    }
+
+
+    inline
+    SymmetricTensor<2,2>
+    symmetrize_single_row (const unsigned int n,
+                          const Tensor<1,2> &t)
+    {
+      switch (n)
+       {
+         case 0:
+         {
+           const double array[3] = { t[0], 0, t[1]/2 };
+           return SymmetricTensor<2,2>(array);
+         }
+         case 1:
+         {
+           const double array[3] = { 0, t[1], t[0]/2 };
+           return SymmetricTensor<2,2>(array);
+         }
+         default:
+         {
+           Assert (false, ExcIndexRange (n, 0, 2));
+           return SymmetricTensor<2,2>();
+         }
+       }
+    }
+
+
+    inline
+    SymmetricTensor<2,3>
+    symmetrize_single_row (const unsigned int n,
+                          const Tensor<1,3> &t)
+    {
+      switch (n)
+       {
+         case 0:
+         {
+           const double array[6] = { t[0], 0, 0, t[1]/2, t[2]/2, 0 };
+           return SymmetricTensor<2,3>(array);
+         }
+         case 1:
+         {
+           const double array[6] = { 0, t[1], 0, t[0]/2, 0, t[2]/2 };
+           return SymmetricTensor<2,3>(array);
+         }
+         case 2:
+         {
+           const double array[6] = { 0, 0, t[2], 0, t[0]/2, t[1]/2 };
+           return SymmetricTensor<2,3>(array);
+         }
+         default:
+         {
+           Assert (false, ExcIndexRange (n, 0, 3));
+           return SymmetricTensor<2,3>();
+         }
+       }
+    }
+  }
+  
+
   template <int dim, int spacedim>
   inline
   typename Vector<dim,spacedim>::symmetric_gradient_type
@@ -3869,12 +3948,8 @@ namespace FEValuesViews
     if (snc == -2)
       return symmetric_gradient_type();
     else if (snc != -1)
-      {
-       gradient_type return_value;
-       return_value[shape_function_data[shape_function].single_nonzero_component_index]
-         = fe_values.shape_gradients[snc][q_point];
-       return symmetrize(return_value);
-      }
+      return symmetrize_single_row (shape_function_data[shape_function].single_nonzero_component_index,
+                                   fe_values.shape_gradients[snc][q_point]);
     else
       {
        gradient_type return_value;