From: Timo Heister <timo.heister@gmail.com>
Date: Wed, 11 Feb 2015 17:15:41 +0000 (-0500)
Subject: Merge pull request #515 from bangerth/terminate-loop-and-error-message
X-Git-Tag: v8.3.0-rc1~483
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2bb584cdebb7a7a78bd1435aecf4b30eeed0c62a;p=dealii.git

Merge pull request #515 from bangerth/terminate-loop-and-error-message

Terminate a loop in a timely manner.

In StraightBoundary::normal_vector(), we currently have a loop that could run
forever. This is not useful. Rather, terminate it after at most 10 iterations
and if it fails output some guidance to what the reason may be.
---

2bb584cdebb7a7a78bd1435aecf4b30eeed0c62a
diff --cc source/grid/tria_boundary.cc
index e296a5f215,61c0ea8f5e..e32916554f
--- a/source/grid/tria_boundary.cc
+++ b/source/grid/tria_boundary.cc
@@@ -628,8 -629,16 +629,16 @@@ normal_vector (const typename Triangula
            for (unsigned int k=0; k<spacedim; ++k)
              H[i][j] += grad_F[i][k] * grad_F[j][k];
  
 -      const Point<facedim> delta_xi = -invert(H) * J;
 +      const Tensor<1,facedim> delta_xi = -invert(H) * J;
        xi += delta_xi;
+       ++iteration;
+ 
+       Assert (iteration<10,
+               ExcMessage("The Newton iteration to find the reference point "
+                          "did not converge in 10 iterations. Do you have a "
+                          "deformed cell? (See the glossary for a definition "
+                          "of what a deformed cell is. You may want to output "
+                          "the vertices of your cell."));
  
        if (delta_xi.norm() < eps)
          break;