]> https://gitweb.dealii.org/ - dealii-svn.git/commitdiff
Add some documentation.
authorbangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Thu, 10 May 2012 16:26:18 +0000 (16:26 +0000)
committerbangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Thu, 10 May 2012 16:26:18 +0000 (16:26 +0000)
git-svn-id: https://svn.dealii.org/trunk@25505 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/include/deal.II/numerics/error_estimator.h

index b1068cda2c6c7d56b4a7eb5842ebc8e596e5536f..61ea08138a895b7ab1e278bdc4677da0a0d56483 100644 (file)
@@ -157,11 +157,22 @@ namespace hp
  *
  *  <li> No other boundary conditions are considered.
  *  </ul>
- *  The object describing the boundary conditions is obtained from the
- *  triangulation.
  *
- *  Thanks go to Franz-Theo Suttmeier for clarifications about boundary
- *  conditions.
+ *  In practice, if you have Robin boundary conditions or are too lazy to
+ *  accurately describe Neumann values, then this is rarely an issue: if you
+ *  don't say anything in the map about a particular part of the boundary then
+ *  the Kelly indicator will simply assume that the solution is correct on
+ *  that part of the boundary and not touch it. Of course, if you have a have
+ *  a Neumann or Robin boundary, that isn't quite true, there is going to be a
+ *  difference between the normal derivative of the numerical solution and the
+ *  Neumann values these normal derivatives should equal. So if we simply
+ *  ignore those parts of the boundary, we'll underestimate the error. In
+ *  practice, this rarely appears to be a problem -- you may not refine the
+ *  cell this time around but you'll probably refine it in the next refinement
+ *  step and everything is good again. After all, for all problems but the
+ *  Laplace equation, the Kelly indicator is only an indicator, not an
+ *  estimator, and so the values it computes are not exact error
+ *  representations anyway.
  *
  *
  *  <h3>Handling of hanging nodes</h3>

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