From: bangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Wed, 23 Jan 2008 16:33:08 +0000 (+0000)
Subject: Document the special case of the constraint x_i=0.
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d31959b0d3c1dd297309439393e106ab66457544;p=dealii-svn.git

Document the special case of the constraint x_i=0.

git-svn-id: https://svn.dealii.org/trunk@15648 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/deal.II/include/dofs/dof_constraints.h b/deal.II/deal.II/include/dofs/dof_constraints.h
index 09abfb5796..0cf61059ee 100644
--- a/deal.II/deal.II/include/dofs/dof_constraints.h
+++ b/deal.II/deal.II/include/dofs/dof_constraints.h
@@ -2,7 +2,7 @@
 //    $Id$
 //    Version: $Name$
 //
-//    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 by the deal.II authors
+//    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 by the deal.II authors
 //
 //    This file is subject to QPL and may not be  distributed
 //    without copyright and license information. Please refer
@@ -48,13 +48,17 @@ class BlockIndices;
  *
  * @image html hp-refinement-simple.png
  *
- * there are three constraints: first $x_2=\frac 12 x_0 + \frac 12 x_1$, then
- * $x_4=\frac 14 x_0 + \frac 34 x_1$, and finally the identity $x_3=x_1$. All
- * three constraints fit the form given above. Similar constraints occur as
- * hanging nodes even if all used finite elements are identical. While they
- * are most frequent for hanging nodes, constraints of the given form appear
- * also in other contexts, see for example the application the @ref step_11
- * "step-11" tutorial program.
+ * there are three constraints: first $x_2=\frac 12 x_0 + \frac 12
+ * x_1$, then $x_4=\frac 14 x_0 + \frac 34 x_1$, and finally the
+ * identity $x_3=x_1$. All three constraints fit the form given
+ * above. Similar constraints occur as hanging nodes even if all used
+ * finite elements are identical. While they are most frequent for
+ * hanging nodes, constraints of the given form appear also in other
+ * contexts, see for example the application the @ref step_11
+ * "step-11" tutorial program. A special case also covered by the
+ * current class is the constraint $x_i=0$ although this constraint on
+ * linear systems is better and more efficiently handled by the
+ * MatrixTools::apply_boundary_values function.
  *
  * The algorithms used in the implementation of this class are described in
  * some detail in the @ref hp_paper "hp paper".