From: Timo Heister <timo.heister@gmail.com>
Date: Fri, 28 Feb 2020 13:51:39 +0000 (-0500)
Subject: documentation: improve level_ghost_owners
X-Git-Tag: v9.2.0-rc1~477^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ce4be5917eeea2d9adf2dfa72643b4a835e4b659;p=dealii.git

documentation: improve level_ghost_owners
---

diff --git a/include/deal.II/distributed/tria_base.h b/include/deal.II/distributed/tria_base.h
index dbfe8d5cdf..0e6507defc 100644
--- a/include/deal.II/distributed/tria_base.h
+++ b/include/deal.II/distributed/tria_base.h
@@ -179,8 +179,9 @@ namespace parallel
      * ghost cell adjacent to the cells of the local processor. In other
      * words, this is the set of subdomain_id() for all ghost cells.
      *
-     * @note If @p i is contained in the list of processor @p j, then @p j
-     * will also be contained in the list of processor @p i.
+     * The returned sets are symmetric, that is if @p i is contained in the
+     * list of processor @p j, then @p j will also be contained in the list of
+     * processor @p i.
      */
     const std::set<types::subdomain_id> &
     ghost_owners() const;
@@ -191,8 +192,14 @@ namespace parallel
      * other words, this is the set of level_subdomain_id() for all level
      * ghost cells.
      *
-     * @note If @p i is contained in the list of processor @p j, then @p j
-     * will also be contained in the list of processor @p i.
+     * The returned sets are symmetric, that is if @p i is contained in the
+     * list of processor @p j, then @p j will also be contained in the list of
+     * processor @p i.
+     *
+     * @note The level ghost owners can only be determined if the multigrid
+     * ownership has been assigned (by setting the
+     * construct_multigrid_hierarchy flag at construction time), otherwise the
+     * returned set will be empty.
      */
     const std::set<types::subdomain_id> &
     level_ghost_owners() const;