From 2edd83aa3c0db084cd4fd13c8c794965c6ffad39 Mon Sep 17 00:00:00 2001 From: Wolfgang Bangerth Date: Sun, 24 May 1998 21:03:10 +0000 Subject: [PATCH] Doc update. git-svn-id: https://svn.dealii.org/trunk@339 0785d39b-7218-0410-832d-ea1e28bc413d --- deal.II/deal.II/include/numerics/vectors.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/deal.II/deal.II/include/numerics/vectors.h b/deal.II/deal.II/include/numerics/vectors.h index 7b8a4877ea..33b4746180 100644 --- a/deal.II/deal.II/include/numerics/vectors.h +++ b/deal.II/deal.II/include/numerics/vectors.h @@ -107,12 +107,19 @@ enum NormType { * in each time step, it is necessary that we also project the boundary * values of the initial values, before projecting them to the whole domain. * + * Obviously, the results of the two schemes for projection are different. + * Usually, when projecting to the boundary first, the $L_2$-norm of the + * difference between original function and projection over the whole domain + * will be larger (factors of five have been observed) while the $L_2$-norm + * of the error integrated over the boundary should of course be less. The + * reverse should also hold if no projection to the boundary is performed. + * * The selection whether the projection to the boundary first is needed is * done with the #project_to_boundary_first# flag passed to the function. * If #false# is given, the additional quadrature formula for faces is * ignored. * - * You should be aware of the fact that if no projection is to the boundary + * You should be aware of the fact that if no projection to the boundary * is requested, a function with zero boundary values may not have zero * boundary values after projection. There is a flag for this especially * important case, which tells the function to enforce zero boundary values -- 2.39.5