From: Wolfgang Bangerth <bangerth@math.tamu.edu>
Date: Wed, 1 May 2013 23:03:42 +0000 (+0000)
Subject: More comments.
X-Git-Tag: v8.0.0~593
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bae0ff9606d3c9b3c284903cb8e5edef40aeb862;p=dealii.git

More comments.


git-svn-id: https://svn.dealii.org/trunk@29421 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/include/deal.II/numerics/vector_tools.h b/deal.II/include/deal.II/numerics/vector_tools.h
index 36e774ca83..fc583d05b3 100644
--- a/deal.II/include/deal.II/numerics/vector_tools.h
+++ b/deal.II/include/deal.II/numerics/vector_tools.h
@@ -1983,6 +1983,15 @@ namespace VectorTools
    * @f{align*}
    *   \textrm{error} = \sqrt{\sum_K \|u-u_h\|_{L_2(K)}^2}
    * @f}
+   * Obviously, if you are interested in computing the $L_1$ norm of the
+   * error, the correct form of the last two lines would have been
+   * @code
+   *    const double total_local_error = local_errors.l1_norm();
+   *    const double total_global_error
+   *      = Utilities::MPI::sum (total_local_error);
+   * @endcode
+   * instead, and similar considerations hold when computing the $L_\infty$
+   * norm of the error.
    *
    * @note Instantiations for this template
    * are provided for some vector types