From 79144c49da0d175b859e5ccb287e5892a62ec028 Mon Sep 17 00:00:00 2001
From: wolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Wed, 29 Aug 2001 15:54:48 +0000
Subject: [PATCH] ConstraintMatrix::is_identity_constrained

git-svn-id: https://svn.dealii.org/trunk@4922 0785d39b-7218-0410-832d-ea1e28bc413d
---
 .../deal.II/include/dofs/dof_constraints.h    | 75 +++++++++++++------
 .../deal.II/source/dofs/dof_constraints.cc    | 29 +++++++
 deal.II/doc/news/2001/c-3-1.html              |  7 ++
 3 files changed, 89 insertions(+), 22 deletions(-)

diff --git a/deal.II/deal.II/include/dofs/dof_constraints.h b/deal.II/deal.II/include/dofs/dof_constraints.h
index cc1c2ab683..ead4f6daf0 100644
--- a/deal.II/deal.II/include/dofs/dof_constraints.h
+++ b/deal.II/deal.II/include/dofs/dof_constraints.h
@@ -301,6 +301,29 @@ class ConstraintMatrix : public Subscriptor
 				      */
     bool is_constrained (const unsigned int index) const;
 
+				     /**
+				      * Return whether the dof is
+				      * constrained, and whether it is
+				      * constrained to only one other
+				      * degree of freedom with weight
+				      * one. The function therefore
+				      * returns whether the degree of
+				      * freedom would simply be
+				      * eliminated in favor of exactly
+				      * one other degree of freedom.
+				      *
+				      * The function returns @p{false}
+				      * if either the degree of
+				      * freedom is not constrained at
+				      * all, or if it is constrained
+				      * to more than one other degree
+				      * of freedom, or if it is
+				      * constrained to only one degree
+				      * of freedom but with a weight
+				      * different from one.
+				      */
+    bool is_identity_constrained (const unsigned int index) const;
+    
 				     /**
 				      * Return the maximum number of
 				      * other dofs that one dof is
@@ -322,37 +345,45 @@ class ConstraintMatrix : public Subscriptor
 				      * constrained to.
 				      */
     unsigned int max_constraint_indirections () const;
-    
+
 				     /**
-				      * Condense a given sparsity pattern. This
-				      * function assumes the uncondensed
-				      * matrix struct to be compressed and the
-				      * one to be filled to be empty. The
-				      * condensed structure is compressed
-				      * afterwards.
+				      * Condense a given sparsity
+				      * pattern. This function assumes
+				      * the uncondensed matrix struct
+				      * to be compressed and the one
+				      * to be filled to be empty. The
+				      * condensed structure is
+				      * compressed afterwards.
 				      *
-				      * The constraint matrix object must be
-				      * closed to call this function.
+				      * The constraint matrix object
+				      * must be closed to call this
+				      * function.
 				      */
     void condense (const SparsityPattern &uncondensed,
 		   SparsityPattern       &condensed) const;
 
 
 				     /**
-				      * This function does much the same as
-				      * the above one, except that it condenses
-				      * the matrix struct 'in-place'. It does
-				      * not remove nonzero entries from the
-				      * matrix but adds those needed for the
-				      * process of distribution of the
-				      * constrained degrees of freedom.
+				      * This function does much the
+				      * same as the above one, except
+				      * that it condenses the matrix
+				      * struct 'in-place'. It does not
+				      * remove nonzero entries from
+				      * the matrix but adds those
+				      * needed for the process of
+				      * distribution of the
+				      * constrained degrees of
+				      * freedom.
 				      *
-				      * Since this function adds new nonzero
-				      * entries to the sparsity pattern, the
-				      * argument must not be compressed. However
-				      * the constraint matrix must be closed.
-				      * The matrix struct is compressed at the
-				      * end of the function.
+				      * Since this function adds new
+				      * nonzero entries to the
+				      * sparsity pattern, the argument
+				      * must not be
+				      * compressed. However the
+				      * constraint matrix must be
+				      * closed.  The matrix struct is
+				      * compressed at the end of the
+				      * function.
 				      */
     void condense (SparsityPattern &sparsity) const;
 
diff --git a/deal.II/deal.II/source/dofs/dof_constraints.cc b/deal.II/deal.II/source/dofs/dof_constraints.cc
index 3f22cc3120..3c281f6c1a 100644
--- a/deal.II/deal.II/source/dofs/dof_constraints.cc
+++ b/deal.II/deal.II/source/dofs/dof_constraints.cc
@@ -1114,6 +1114,35 @@ bool ConstraintMatrix::is_constrained (const unsigned int index) const
 
 
 
+bool ConstraintMatrix::is_identity_constrained (const unsigned int index) const 
+{
+  if (sorted == true)
+    {
+      ConstraintLine index_comparison;
+      index_comparison.line = index;
+
+      const std::vector<ConstraintLine>::const_iterator
+	p = std::lower_bound (lines.begin (),
+			      lines.end (),
+			      index_comparison);
+      return ((p->line == index) &&
+	      (p->entries.size() == 1) &&
+	      (p->entries[0].second == 1.0));
+    }
+  else
+    {
+      for (std::vector<ConstraintLine>::const_iterator i=lines.begin();
+	   i!=lines.end(); ++i)
+	if (i->line == index)
+	  return ((i->entries.size() == 1) &&
+		  (i->entries[0].second == 1.0));
+
+      return false;
+    };
+};
+
+
+
 unsigned int ConstraintMatrix::max_constraint_indirections () const 
 {
   unsigned int return_value = 0;
diff --git a/deal.II/doc/news/2001/c-3-1.html b/deal.II/doc/news/2001/c-3-1.html
index f4963f8afd..47587d8f4a 100644
--- a/deal.II/doc/news/2001/c-3-1.html
+++ b/deal.II/doc/news/2001/c-3-1.html
@@ -573,6 +573,13 @@ documentation, etc</a>.
 <h3>deal.II</h3>
 
 <ol>
+  <li> <p>
+       New: Member function
+       <code class="member">ConstraintMatrix::is_identity_constrained</code>.
+       <br>
+       (WB 2001/08/29)
+       </p>
+
   <li> <p>
        Fixed: in a rather rare case, some work was done twice in the
        <code class="class">KellyErrorEstimator</code> class when in
-- 
2.39.5