]> https://gitweb.dealii.org/ - dealii.git/commitdiff
Update docs.
authorWolfgang Bangerth <bangerth@math.tamu.edu>
Mon, 21 Mar 2005 21:03:19 +0000 (21:03 +0000)
committerWolfgang Bangerth <bangerth@math.tamu.edu>
Mon, 21 Mar 2005 21:03:19 +0000 (21:03 +0000)
git-svn-id: https://svn.dealii.org/trunk@10193 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/deal.II/include/numerics/vectors.h

index 71673f92cb2a18c76d64214ed00f1dbd5968cafd..de4a7596f3571e95293ab651f71399dd565dfb82 100644 (file)
@@ -2,7 +2,7 @@
 //    $Id$
 //    Version: $Name$
 //
-//    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004 by the deal.II authors
+//    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 by the deal.II authors
 //
 //    This file is subject to QPL and may not be  distributed
 //    without copyright and license information. Please refer
@@ -879,26 +879,37 @@ class VectorTools
                                  const Point<dim>&      point);
     
                                     /**
-                                     * Mean-value filter for Stokes.
-                                     * The pressure in Stokes'
+                                     * Subtract the (algebraic) mean value
+                                     * from a vector. This function is most
+                                     * frequently used as a mean-value filter
+                                     * for Stokes: The pressure in Stokes'
                                      * equations with only Dirichlet
-                                     * boundaries for the velocities
-                                     * is determined up to a constant
-                                     * only. This function allows to
-                                     * subtract the mean value of the
-                                     * pressure. It is usually called
-                                     * in a preconditioner and
-                                     * generates updates with mean
-                                     * value zero. The mean value is
-                                     * understood in the l1-sense.
+                                     * boundaries for the velocities is only
+                                     * determined up to a constant. This
+                                     * function allows to subtract the mean
+                                     * value of the pressure. It is usually
+                                     * called in a preconditioner and
+                                     * generates updates with mean value
+                                     * zero. The mean value is computed as
+                                     * the mean value of the degree of
+                                     * freedom values as given by the input
+                                     * vector; they are not weighted by the
+                                     * area of cells, i.e. the mean is
+                                     * computed as <tt>sum_i v_i</tt>, rather
+                                     * than as <tt>int_Omega v(x) = int_Omega
+                                     * sum_i v_i phi_i(x)</tt>.
                                      *
-                                     * Apart from the vector @p v to
-                                     * operate on, this function
-                                     * takes a bit vector. This has a
-                                     * true entry for every component
-                                     * for which the mean value shall
-                                     * be computed and later
-                                     * subtracted.
+                                     * Apart from the vector @p v to operate
+                                     * on, this function takes a bit
+                                     * vector. This has a true entry for
+                                     * every component for which the mean
+                                     * value shall be computed and later
+                                     * subtracted. The argument is used to
+                                     * denote which components of the
+                                     * solution vector correspond to the
+                                     * pressure, and avoid touching all other
+                                     * components of the vector, such as the
+                                     * velocity components.
                                      */
     static void subtract_mean_value(Vector<double>          &v,
                                    const std::vector<bool> &p_select);

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