Change the tolerances for when considering a cell a translation of the previous one...

git-svn-id: https://svn.dealii.org/trunk@18479 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/deal.II/source/fe/fe_values.cc b/deal.II/deal.II/source/fe/fe_values.cc
index f35821185747489a131971bca04c2a9dba092635..8fc34eea0951bccbaf894465f26c90e8ad7d8bd4 100644 (file)
--- a/deal.II/deal.II/source/fe/fe_values.cc
+++ b/deal.II/deal.II/source/fe/fe_values.cc
@@ -3269,18 +3269,27 @@ FEValuesBase<dim,spacedim>::check_cell_similarity
  
                                   // test for translation
   {
-                                  // otherwise, go through the vertices and
-                                  // check... The cell is a translation of
-                                  // the previous one in case the distance
-                                  // between the individual vertices in the
-                                  // two cell is the same for all the
+                                  // otherwise, go through the vertices
+                                  // and check... The cell is a
+                                  // translation of the previous one in
+                                  // case the distance between the
+                                  // individual vertices in the two
+                                  // cell is the same for all the
                                   // vertices. So do the check by first
                                   // getting the distance on the first
-                                  // vertex, and then checking whether all
-                                  // others have the same.
+                                  // vertex, and then checking whether
+                                  // all others have the same down to
+                                  // rounding errors (we have to be
+                                  // careful here because the
+                                  // calculation of the displacement
+                                  // between one cell and the next can
+                                  // already result in the loss of one
+                                  // or two digits), so we choose 1e-12
+                                  // times the distance between the
+                                  // zeroth vertices here.
     bool is_translation = true;
     const Point<spacedim> dist = cell->vertex(0) - present_cell->vertex(0);
-    const double tolerance = 1e-30 * dist.norm_square();
+    const double tolerance = 1e-24 * dist.norm_square();
     for (unsigned int i=1; i<GeometryInfo<dim>::vertices_per_cell; ++i)
       {
        Point<spacedim> dist_new = cell->vertex(i) - present_cell->vertex(i) - dist;