From: bangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Wed, 27 Mar 2013 14:22:53 +0000 (+0000)
Subject: Outlaw the use of local_range() and in_local_range() if the vector is not contiguous... 
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=edbf7a5092b71a9bce6c800287ef3232a510c396;p=dealii-svn.git

Outlaw the use of local_range() and in_local_range() if the vector is not contiguous on the current processor.

git-svn-id: https://svn.dealii.org/trunk@29072 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/include/deal.II/lac/trilinos_vector_base.h b/deal.II/include/deal.II/lac/trilinos_vector_base.h
index fa32d9de6c..134bc47064 100644
--- a/deal.II/include/deal.II/lac/trilinos_vector_base.h
+++ b/deal.II/include/deal.II/lac/trilinos_vector_base.h
@@ -488,9 +488,24 @@ namespace TrilinosWrappers
      * that is stored locally. If
      * this is a sequential vector,
      * then the result will be the
-     * pair (0,N), otherwise it will
-     * be a pair (i,i+n), where
-     * <tt>n=local_size()</tt>.
+     * pair <code>(0,N)</code>, otherwise it will
+     * be a pair <code>(i,i+n)</code>, where
+     * <code>n=local_size()</code> and <code>i</code> is the first
+     * element of the vector stored on this processor, corresponding
+     * to the half open interval $[i,i+n)$
+     *
+     * @note The description above is true most of the time, but
+     * not always. In particular, Trilinos vectors need not store
+     * contiguous ranges of elements such as $[i,i+n)$. Rather, it
+     * can store vectors where the elements are distributed in
+     * an arbitrary way across all processors and each processor
+     * simply stores a particular subset, not necessarily contiguous.
+     * In this case, this function clearly makes no sense since it
+     * could, at best, return a range that includes all elements
+     * that are stored locally. Thus, the function only succeeds
+     * if the locally stored range is indeed contiguous. It will
+     * trigger an assertion if the local portion of the vector
+     * is not contiguous.
      */
     std::pair<unsigned int, unsigned int> local_range () const;
 
@@ -498,6 +513,9 @@ namespace TrilinosWrappers
      * Return whether @p index is in
      * the local range or not, see
      * also local_range().
+     *
+     * @note The same limitation for the applicability of this
+     * function applies as listed in the documentation of local_range().
      */
     bool in_local_range (const unsigned int index) const;
 
@@ -1172,7 +1190,7 @@ namespace TrilinosWrappers
   bool
   VectorBase::in_local_range (const unsigned int index) const
   {
-    std::pair<unsigned int, unsigned int> range = local_range();
+    const std::pair<unsigned int, unsigned int> range = local_range();
 
     return ((index >= range.first) && (index <  range.second));
   }
@@ -1490,6 +1508,12 @@ namespace TrilinosWrappers
     int begin, end;
     begin = vector->Map().MinMyGID();
     end = vector->Map().MaxMyGID()+1;
+
+    Assert (end-begin == vector->Map().NumMyElements(),
+            ExcMessage ("This function only makes sense if the elements that this "
+                        "vector stores on the current processor form a contiguous range. "
+                        "This does not appear to be the case for the current vector."));
+
     return std::make_pair (begin, end);
   }