From: Daniel Arndt <arndtd@ornl.gov>
Date: Thu, 26 Sep 2019 01:05:37 +0000 (-0400)
Subject: Document direction parameter for periodic constraints
X-Git-Tag: v9.2.0-rc1~1019^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F8859%2Fhead;p=dealii.git

Document direction parameter for periodic constraints
---

diff --git a/include/deal.II/dofs/dof_tools.h b/include/deal.II/dofs/dof_tools.h
index fd8c77abbf..772a23c44b 100644
--- a/include/deal.II/dofs/dof_tools.h
+++ b/include/deal.II/dofs/dof_tools.h
@@ -1218,7 +1218,8 @@ namespace DoFTools
    *
    * This function tries to match all faces belonging to the first boundary
    * with faces belonging to the second boundary with the help of
-   * orthogonal_equality().
+   * orthogonal_equality(). More precisely, faces with coordinates only
+   * differing in the @p direction component are identified.
    *
    * If this matching is successful it constrains all DoFs associated with the
    * 'first' boundary to the respective DoFs of the 'second' boundary
@@ -1256,7 +1257,8 @@ namespace DoFTools
    * boundary_ids this function defines a 'left' boundary as all faces with
    * local face index <code>2*dimension</code> and boundary indicator @p b_id
    * and, similarly, a 'right' boundary consisting of all face with local face
-   * index <code>2*dimension+1</code> and boundary indicator @p b_id.
+   * index <code>2*dimension+1</code> and boundary indicator @p b_id. Faces with
+   * coordinates only differing in the @p direction component are identified.
    *
    * @note This version of make_periodicity_constraints  will not work on
    * meshes with cells not in
diff --git a/include/deal.II/grid/grid_tools.h b/include/deal.II/grid/grid_tools.h
index fb287ace42..23cba652cc 100644
--- a/include/deal.II/grid/grid_tools.h
+++ b/include/deal.II/grid/grid_tools.h
@@ -2571,7 +2571,9 @@ namespace GridTools
    * boundary_ids this function defines a 'left' boundary as all faces with
    * local face index <code>2*dimension</code> and boundary indicator @p b_id
    * and, similarly, a 'right' boundary consisting of all face with local face
-   * index <code>2*dimension+1</code> and boundary indicator @p b_id.
+   * index <code>2*dimension+1</code> and boundary indicator @p b_id. Faces
+   * with coordinates only differing in the @p direction component are
+   * identified.
    *
    * This function will collect periodic face pairs on the coarsest mesh level
    * and add them to @p matched_pairs leaving the original contents intact.