From 9dcc9f2cb436dc3175b2aa6c27b30dabee8de108 Mon Sep 17 00:00:00 2001
From: Martin Kronbichler <kronbichler@lnm.mw.tum.de>
Date: Thu, 5 Dec 2013 10:45:13 +0000
Subject: [PATCH] Avoid cycles in constraint.

git-svn-id: https://svn.dealii.org/trunk@31897 0785d39b-7218-0410-832d-ea1e28bc413d
---
 tests/deal.II/assemble_matrix_parallel_04.cc | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/tests/deal.II/assemble_matrix_parallel_04.cc b/tests/deal.II/assemble_matrix_parallel_04.cc
index 9c4d594fbd..4713c3c936 100644
--- a/tests/deal.II/assemble_matrix_parallel_04.cc
+++ b/tests/deal.II/assemble_matrix_parallel_04.cc
@@ -264,14 +264,21 @@ void LaplaceProblem<dim>::setup_system ()
 
   constraints.clear ();
 
-  // add a constraint that expands over most of the domain, which should
-  // create many conflicts
-  constraints.add_line(3);
-  for (unsigned int i=5; i<dof_handler.n_dofs(); i+=11)
-    constraints.add_entry(3, i, -0.5);
-
   DoFTools::make_hanging_node_constraints (dof_handler, constraints);
 
+  // add a constraint that expands over most of the domain, which should
+  // create many conflicts. Avoid cycles and do not constrain to entries
+  // already constrained
+  for (unsigned int c=0; c<dof_handler.n_dofs(); ++c)
+    if (constraints.is_constrained(c) == false)
+      {
+        constraints.add_line(c);
+        for (unsigned int i=5; i<dof_handler.n_dofs(); i+=11)
+          if (constraints.is_constrained(i) == false)
+            constraints.add_entry(c, i, -0.5);
+        break;
+      }
+
   // add boundary conditions as inhomogeneous constraints here, do it after
   // having added the hanging node constraints in order to be consistent and
   // skip dofs that are already constrained (i.e., are hanging nodes on the
-- 
2.39.5