From: Wolfgang Bangerth Date: Mon, 21 Mar 2005 21:03:19 +0000 (+0000) Subject: Update docs. X-Git-Tag: v8.0.0~14344 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3353c7a34b908107a49f918dc93b363b2d6f5b07;p=dealii.git Update docs. git-svn-id: https://svn.dealii.org/trunk@10193 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/deal.II/include/numerics/vectors.h b/deal.II/deal.II/include/numerics/vectors.h index 71673f92cb..de4a7596f3 100644 --- a/deal.II/deal.II/include/numerics/vectors.h +++ b/deal.II/deal.II/include/numerics/vectors.h @@ -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& 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 sum_i v_i, rather + * than as int_Omega v(x) = int_Omega + * sum_i v_i phi_i(x). * - * 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 &v, const std::vector &p_select);