From e4c188a8457e33579c4b91287d701edc624af919 Mon Sep 17 00:00:00 2001
From: wolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Mon, 28 Feb 2000 16:29:39 +0000
Subject: [PATCH] Add a safety check whether constrained nodes are constrained
 to other constraints, which is not allowed.

git-svn-id: https://svn.dealii.org/trunk@2502 0785d39b-7218-0410-832d-ea1e28bc413d
---
 .../deal.II/include/dofs/dof_constraints.h    | 11 +++++-
 .../deal.II/source/dofs/dof_constraints.cc    | 34 ++++++++++++++++++-
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/deal.II/deal.II/include/dofs/dof_constraints.h b/deal.II/deal.II/include/dofs/dof_constraints.h
index 98ecb50dd1..cae4cac49f 100644
--- a/deal.II/deal.II/include/dofs/dof_constraints.h
+++ b/deal.II/deal.II/include/dofs/dof_constraints.h
@@ -332,6 +332,14 @@ class ConstraintMatrix : public Subscriptor
 		    << "The entry for the indices " << arg1 << " and "
 		    << arg2 << " already exists, but the values "
 		    << arg3 << " (old) and " << arg4 << " (new) differ.");
+				     /**
+				      * Exception
+				      */
+    DeclException2 (ExcDoFConstrainedToConstrainedDoF,
+		    int, int,
+		    << "You tried to constrain DoF " << arg1
+		    << " to DoF " << arg2
+		    << ", but that one is also constrained. This is not allowed!");
     
   private:
 
@@ -339,7 +347,8 @@ class ConstraintMatrix : public Subscriptor
 				      * This class represents one line of a
 				      * constraint matrix.
 				      */
-    struct ConstraintLine {
+    struct ConstraintLine
+    {
 					 /**
 					  * Number of this line. Since only very
 					  * few lines are stored, we can not
diff --git a/deal.II/deal.II/source/dofs/dof_constraints.cc b/deal.II/deal.II/source/dofs/dof_constraints.cc
index 2b9e6178f8..0c259e9811 100644
--- a/deal.II/deal.II/source/dofs/dof_constraints.cc
+++ b/deal.II/deal.II/source/dofs/dof_constraints.cc
@@ -98,7 +98,14 @@ void ConstraintMatrix::close () {
 				   endl = lines.end();
   for (; line!=endl; ++line)
     {
-				       // first remove zero entries
+				       // first remove zero
+				       // entries. that would mean
+				       // that in the linear
+				       // constraint for a node,
+				       // x_i = ax_1 + bx_2 + ...,
+				       // another node times 0
+				       // appears. obviously,
+				       // 0*something can be omitted
       line->entries.erase (remove_if (line->entries.begin(),
 				      line->entries.end(),
 				      compose1 (bind2nd (equal_to<double>(), 0),
@@ -111,6 +118,31 @@ void ConstraintMatrix::close () {
   
 				   // sort the lines
   sort (lines.begin(), lines.end());
+
+#ifdef DEBUG
+				   // if in debug mode: check that no
+				   // dof is constraint to another dof
+				   // that is also constrained
+  for (vector<ConstraintLine>::const_iterator line=lines.begin();
+       line!=lines.end(); ++line)
+    for (vector<pair<unsigned int,double> >::const_iterator entry=line->entries.begin();
+	 entry!=line->entries.end(); ++entry)
+      {
+					 // make sure that
+					 // entry->first is not the
+					 // index of a line itself
+	const ConstraintLine test_line = { entry->first,
+					   vector<pair<unsigned int,double> >() };
+	const vector<ConstraintLine>::const_iterator
+	  test_line_position = lower_bound (lines.begin(),
+					    lines.end(),
+					    test_line);
+	Assert ((test_line_position == lines.end())
+		||
+		(test_line_position->line != entry->first),
+		ExcDoFConstrainedToConstrainedDoF(line->line, entry->first));
+      };
+#endif
   
   sorted = true;
 };
-- 
2.39.5