]> https://gitweb.dealii.org/ - dealii-svn.git/commitdiff
Doc update.
authorwolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Fri, 11 Dec 1998 10:24:40 +0000 (10:24 +0000)
committerwolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Fri, 11 Dec 1998 10:24:40 +0000 (10:24 +0000)
git-svn-id: https://svn.dealii.org/trunk@701 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/deal.II/include/fe/fe.h

index 836f4c892a436c2ead7dd8f285f0e23510d496ad..144d29b2ec78ccd098a28a003df59ee7a696671e 100644 (file)
@@ -309,7 +309,10 @@ struct FiniteElementBase :
                                      * to the destination cell, i.e. the
                                      * unrefined one, while the column indices
                                      * are for the refined cell's degrees of
-                                     * freedom.
+                                     * freedom. The application of this matrix
+                                     * is therefore usually its being
+                                     * multiplied by the vector of nodal values
+                                     * on the child.
                                      *
                                      * In essence, using the matrices from the
                                      * children to the mother cell amounts to
@@ -329,6 +332,41 @@ struct FiniteElementBase :
                                      * contributions of each child into the
                                      * nodal value vector of the mother cell.
                                      *
+                                     * While we could avoid this and rather add
+                                     * up the contributions of each child for
+                                     * nodes that are interior of the mother
+                                     * cell, we can't for nodes on the boundary
+                                     * of the mother cell. The reason for this
+                                     * is that we know how many children may
+                                     * contribute to the interpolated nodal
+                                     * value of an interior degree of freedom.
+                                     * However, we don't know for dofs on the
+                                     * boundary, for which we only know how many
+                                     * children from each side of the face
+                                     * contribute, but we would have to look out
+                                     * of the cell to know how many neighbors
+                                     * there are and then, still, we would have
+                                     * to have two different interpolation
+                                     * routines for local interpolation and for
+                                     * the contribution of a cell to a global
+                                     * interpolation if we wanted to compute
+                                     * that by adding up local contributions.
+                                     *
+                                     * Because of this problem, we chose to
+                                     * write rather than add the contributions
+                                     * of each cell to the interpolation onto
+                                     * the mother cell. However, there now is
+                                     * another problem which appears when using
+                                     * discontinuous finite elements. The
+                                     * process of 'writing' assumed that we
+                                     * get the same result for each degree of
+                                     * freedom from each of the children, such
+                                     * that 'over'writing would not destroy
+                                     * information; when using discontinuous
+                                     * elements, this assumption is violated.
+                                     *
+                                     * SOLUTION? NOT YET MADE UP!
+                                     *
                                      * To compute the interpolation of a
                                      * finite element field to a cell, you
                                      * may use the #get_interpolated_dof_values#

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