From 7e4d95bf317748490ab15c94a127b80f5d325031 Mon Sep 17 00:00:00 2001 From: wolf Date: Fri, 6 May 2005 19:49:42 +0000 Subject: [PATCH] Document the problems with hanging nodes and boundary conditions. git-svn-id: https://svn.dealii.org/trunk@10652 0785d39b-7218-0410-832d-ea1e28bc413d --- deal.II/doc/news/changes.html | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/deal.II/doc/news/changes.html b/deal.II/doc/news/changes.html index 7a47059cf6..a71ef52ccd 100644 --- a/deal.II/doc/news/changes.html +++ b/deal.II/doc/news/changes.html @@ -42,6 +42,25 @@ inconvenience this causes.
    +
  1. Changed: The way boundary constraints were handled in the step-17 + tutorial program was conceptually flawed. We tried to eliminate boundary + nodes locally on the cell level, and hanging node constraints subsequently + when transferring into the global matrix. However, this doesn't work in + general: the elimination of hanging node constraints could re-populate rows + and columns that had already been vacated during boundary node + elimination. At the end of a long though process, we came to the conclusion + that it is impossible to revert the traditional order of operations: first + eliminate all hanging node constraints, then eliminate all boundary + nodes. This leads to a situation where the MatrixTools::local_apply_boundary_values function is + not very useful any more, except for the special case where there are no + hanging nodes. The step-17 example program has therefore been changed to use + the MatrixTools::apply_boundary_values function + again, though hanging node elimination still happens during transfer into + the global matrix. +
    (WB 2005/05/05) +

    +
  2. Changed: The class MGCoarseGridLACIteration lost two template arguments. Since the matrix and preconditioner are now stored in -- 2.39.5