From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Sun, 13 Aug 2017 00:22:23 +0000 (-0600)
Subject: Update documentation.
X-Git-Tag: v9.0.0-rc1~1279^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F4806%2Fhead;p=dealii.git

Update documentation.
---

diff --git a/include/deal.II/dofs/dof_accessor.templates.h b/include/deal.II/dofs/dof_accessor.templates.h
index b7c55d4eee..881af450ac 100644
--- a/include/deal.II/dofs/dof_accessor.templates.h
+++ b/include/deal.II/dofs/dof_accessor.templates.h
@@ -3781,16 +3781,15 @@ DoFCellAccessor<DoFHandlerType,level_dof_access>::set_active_fe_index (const uns
                       "children because no degrees of freedom will be assigned "
                       "to this cell."));
 
-  if (i != DoFHandlerType::default_fe_index)
-    Assert ((dynamic_cast<const dealii::DoFHandler<DoFHandlerType::dimension,DoFHandlerType::space_dimension>*>
-             (this->dof_handler) != nullptr)
-            ||
-            this->is_locally_owned(),
-            ExcMessage ("You can only set active_fe_index information on cells "
-                        "that are locally owned. On ghost cells, this information "
-                        "will automatically be propagated from the owning process "
-                        "of that cell, and there is no information at all on "
-                        "artificial cells."));
+  Assert ((dynamic_cast<const dealii::DoFHandler<DoFHandlerType::dimension,DoFHandlerType::space_dimension>*>
+           (this->dof_handler) != nullptr)
+          ||
+          this->is_locally_owned(),
+          ExcMessage ("You can only set active_fe_index information on cells "
+                      "that are locally owned. On ghost cells, this information "
+                      "will automatically be propagated from the owning process "
+                      "of that cell, and there is no information at all on "
+                      "artificial cells."));
   dealii::internal::DoFCellAccessor::Implementation::set_active_fe_index (*this, i);
 }
 
diff --git a/include/deal.II/hp/dof_handler.h b/include/deal.II/hp/dof_handler.h
index a00afc782f..a34a838058 100644
--- a/include/deal.II/hp/dof_handler.h
+++ b/include/deal.II/hp/dof_handler.h
@@ -132,19 +132,26 @@ namespace hp
    *
    * When this class is used with either a parallel::shared::Triangulation
    * or a parallel::distributed::Triangulation, you can only set active
-   * FE indices on cells that are locally owned or that are ghost cells,
+   * FE indices on cells that are locally owned,
    * using a call such as <code>cell-@>set_active_fe_index(...)</code>.
-   * On the other hand, setting the active FE index on artificial cells
-   * is not allowed.
+   * On the other hand, setting the active FE index on ghost
+   * or artificial cells is not allowed.
    *
-   * However, setting the index on ghost cells has no real effect: whenever
+   * Ghost cells do acquire the information what element
+   * is active on them, however: whenever
    * you call hp::DoFHandler::distribute_dofs(), all processors that
    * participate in the parallel mesh exchange information in such a way
    * that the active FE index on ghost cells equals the active FE index
    * that was set on that processor that owned that particular ghost cell.
-   * In other words, information that may have previously been set on
-   * ghost cells is overwritten so that the active FE index there is
-   * consistent with the value on the processor that owns the cell.
+   * Consequently, one can <i>query</i> the @p active_fe_index on ghost
+   * cells, just not set it by hand.
+   *
+   * On artificial cells, no information is available about the
+   * @p active_fe_index used there. That's because we don't even know
+   * whether these cells exist at all, and even if they did, the
+   * current processor does not know anything specific about them.
+   * See @ref GlossArtificialCell "the glossary entry on artificial cells"
+   * for more information.
    *
    *
    * @ingroup dofs