Augment documentation.

git-svn-id: https://svn.dealii.org/trunk@26568 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/include/deal.II/dofs/dof_renumbering.h b/deal.II/include/deal.II/dofs/dof_renumbering.h
index 6b7d838b1f07e598671b71105722b42efc20fb6b..341d1da45e2a19ddc2c1496d3a1b14e92b240e46 100644 (file)
--- a/deal.II/include/deal.II/dofs/dof_renumbering.h
+++ b/deal.II/include/deal.II/dofs/dof_renumbering.h
@@ -849,6 +849,24 @@ namespace DoFRenumbering
                                     * Sort the degrees of freedom by
                                     * block. It does the same
                                     * thing as the above function.
+                                   *
+                                   * This function only succeeds if each of
+                                   * the elements in the hp::FECollection
+                                   * attached to the hp::DoFHandler argument
+                                   * has exactly the same number of blocks
+                                   * (see @ref GlossBlock "the glossary" for
+                                   * more information). Note that this is not
+                                   * always given: while the hp::FECollection
+                                   * class ensures that all of its elements
+                                   * have the same number of vector
+                                   * components, they need not have the same
+                                   * number of blocks. At the same time, this
+                                   * function here needs to match individual
+                                   * blocks across elements and therefore
+                                   * requires that elements have the same
+                                   * number of blocks and that subsequent
+                                   * blocks in one element have the same
+                                   * meaning as in another element.
                                     */
   template <int dim>
   void