]> https://gitweb.dealii.org/ - dealii.git/commitdiff
Add warning about reading in grids that have hanging nodes.
authorWolfgang Bangerth <bangerth@math.tamu.edu>
Fri, 6 Jun 2003 20:18:35 +0000 (20:18 +0000)
committerWolfgang Bangerth <bangerth@math.tamu.edu>
Fri, 6 Jun 2003 20:18:35 +0000 (20:18 +0000)
git-svn-id: https://svn.dealii.org/trunk@7762 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/deal.II/include/grid/grid_in.h

index 4e2efeefa62824cc94e11a1706cc42a57a0de1f4..6461cb6ee4ca7b9971ea9e1f3addc74beac942ef 100644 (file)
@@ -34,6 +34,20 @@ class SubCellData;
  * format for grid data. Any numerical data after the block of
  * topological information is ignored.
  *
+ * Since the coarse mesh fed into a @p{Triangulation} object cannot
+ * have hanging nodes, strange things will happen if the input file
+ * has them. This is due to the fact that most mesh description
+ * formats do not store neighborship information between cells, so the
+ * grid reading functions have to regenerate it. They do so by
+ * checking whether two cells have a common face. If there are hanging
+ * nodes in a triangulation, adjacent cells have no common face, so
+ * the grid reader concludes that the adjacent cells have no neighbors
+ * along these faces and must therefore be at the boundary. In effect,
+ * an internal crack of the domain is introduced this way. Since such
+ * cases are very hard to detect, the library does not make any
+ * attempt to abort on such situations, and you will get a
+ * triangulation that probably does not do what you want.
+ *
  * Note: if you experience unexpected problems with the use of this
  * class, be sure to read the documentation right until the end, and
  * also read the documentation of the @ref{GridReordering} class.

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