From 74d278a79e40ee4ea60d57a9d9f4569c3f507043 Mon Sep 17 00:00:00 2001 From: Wolfgang Bangerth Date: Wed, 13 Sep 2017 07:44:13 -0600 Subject: [PATCH] Add to the documentation. --- include/deal.II/dofs/dof_accessor.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/include/deal.II/dofs/dof_accessor.h b/include/deal.II/dofs/dof_accessor.h index 104f07f85c..f647257a03 100644 --- a/include/deal.II/dofs/dof_accessor.h +++ b/include/deal.II/dofs/dof_accessor.h @@ -1694,6 +1694,15 @@ public: * indices on non-active cells since they do not have finite element spaces * associated with them without having any degrees of freedom. Consequently, * this function will produce an exception when called on non-active cells. + * + * @note When using parallel meshes, either through the + * parallel::shared::Triangulation or parallel::distributed::Triangulation + * classes, it is only allowed to call this function on locally + * owned or ghost cells. No information is available on artificial cells. + * Furthermore, @p active_fe_index information is exchanged from locally + * owned cells on one processor to other processors where they may be + * ghost cells, during the call to hp::DoFHandler::distribute_dofs(). + * See the documentation of hp::DoFHandler for more information. */ unsigned int active_fe_index () const; @@ -1709,6 +1718,18 @@ public: * indices to non-active cells since they do not have finite element spaces * associated with them without having any degrees of freedom. Consequently, * this function will produce an exception when called on non-active cells. + * + * @note When using parallel meshes, either through the + * parallel::shared::Triangulation or parallel::distributed::Triangulation + * classes, it is only allowed to call this function on locally + * owned cells (see @ref GlossLocallyOwnedCell "this glossary entry"). This + * is because otherwise a common source of errors would be if one + * processor sets a different @p active_fe_index on a ghost cell than + * the processor that actually owns the cell does. To avoid this mistake, + * one can only set @p active_fe_index information on locally owned + * cells, and this information is then mirrored to all processors that + * have this cell as a ghost cell -- see the documentation of the + * hp::DoFHandler class. */ void set_active_fe_index (const unsigned int i) const; /** -- 2.39.5