From 65c89f163c140daa9dfdee524984d3cfe71c9ed0 Mon Sep 17 00:00:00 2001
From: Simon Sticko <simon@sticko.se>
Date: Wed, 2 Jun 2021 15:24:37 +0200
Subject: [PATCH] Add a 0-dimensional face support point on FE_Q<1>.

In several places QProjector is used to map the dim-1 dimensional face
support points to dim dimensional points, but this is not possible in
1D because unit_face_support_points currently contains no points for
FE_Q<1>. Add a single 0-dimensional point to unit_face_support_points
to fix this.
---
 source/fe/fe_q_base.cc              |  9 +++++----
 tests/fe/fe_data_test.output        |  6 +++---
 tests/fe/fe_support_points_q.cc     |  2 ++
 tests/fe/fe_support_points_q.output | 10 ++++++++++
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/source/fe/fe_q_base.cc b/source/fe/fe_q_base.cc
index 10ceee4f0a..f0eb0cd8e0 100644
--- a/source/fe/fe_q_base.cc
+++ b/source/fe/fe_q_base.cc
@@ -978,10 +978,6 @@ void
 FE_Q_Base<dim, spacedim>::initialize_unit_face_support_points(
   const std::vector<Point<1>> &points)
 {
-  // no faces in 1d, so nothing to do
-  if (dim == 1)
-    return;
-
   // TODO: the implementation makes the assumption that all faces have the
   // same number of dofs
   AssertDimension(this->n_unique_faces(), 1);
@@ -990,6 +986,11 @@ FE_Q_Base<dim, spacedim>::initialize_unit_face_support_points(
   this->unit_face_support_points[face_no].resize(
     Utilities::fixed_power<dim - 1>(q_degree + 1));
 
+  // In 1D, there is only one 0-dimensional support point, so there is nothing
+  // more to be done.
+  if (dim == 1)
+    return;
+
   // find renumbering of faces and assign from values of quadrature
   const std::vector<unsigned int> face_index_map =
     FETools::lexicographic_to_hierarchic_numbering<dim - 1>(q_degree);
diff --git a/tests/fe/fe_data_test.output b/tests/fe/fe_data_test.output
index 95b0ee1f0b..e1f992eb8b 100644
--- a/tests/fe/fe_data_test.output
+++ b/tests/fe/fe_data_test.output
@@ -50,7 +50,7 @@ DEAL::blocks=1:[2]->2
 DEAL::degree=1
 DEAL::conformity= Hcurl Hdiv H1
 DEAL::unit_support_points=2
-DEAL::unit_face_support_points=0
+DEAL::unit_face_support_points=1
 DEAL::generalized_support_points=2
 DEAL::face_to_equivalent_cell_index: 0
 DEAL::face_to_cell_index: 0
@@ -76,7 +76,7 @@ DEAL::blocks=1:[3]->3
 DEAL::degree=2
 DEAL::conformity= Hcurl Hdiv H1
 DEAL::unit_support_points=3
-DEAL::unit_face_support_points=0
+DEAL::unit_face_support_points=1
 DEAL::generalized_support_points=3
 DEAL::face_to_equivalent_cell_index: 0
 DEAL::face_to_cell_index: 0
@@ -102,7 +102,7 @@ DEAL::blocks=1:[5]->5
 DEAL::degree=4
 DEAL::conformity= Hcurl Hdiv H1
 DEAL::unit_support_points=5
-DEAL::unit_face_support_points=0
+DEAL::unit_face_support_points=1
 DEAL::generalized_support_points=5
 DEAL::face_to_equivalent_cell_index: 0
 DEAL::face_to_cell_index: 0
diff --git a/tests/fe/fe_support_points_q.cc b/tests/fe/fe_support_points_q.cc
index 5c2a4250a9..b97018df0f 100644
--- a/tests/fe/fe_support_points_q.cc
+++ b/tests/fe/fe_support_points_q.cc
@@ -25,6 +25,8 @@ main()
 {
   initlog();
 
+  CHECK_ALL(Q, 1, 1);
+
   CHECK_ALL(Q, 1, 2);
   CHECK_ALL(Q, 2, 2);
   CHECK_ALL(Q, 3, 2);
diff --git a/tests/fe/fe_support_points_q.output b/tests/fe/fe_support_points_q.output
index 11cc9484c5..c3532a4277 100644
--- a/tests/fe/fe_support_points_q.output
+++ b/tests/fe/fe_support_points_q.output
@@ -1,4 +1,14 @@
 
+DEAL::Q1<1> cell support points
+DEAL::0.00
+DEAL::1.00
+DEAL::Q1<1> face 0 support points
+DEAL::0.00
+DEAL::Q1<1> face 1 support points
+DEAL::1.00
+DEAL::Q1<1> cell generalized support points
+DEAL::0.00
+DEAL::1.00
 DEAL::Q1<2> cell support points
 DEAL::0.00 0.00
 DEAL::1.00 0.00
-- 
2.39.5