diff --git a/doc/istl/comm/Makefile.am b/doc/istl/comm/Makefile.am
index 30ea425e2c5a0a170d610a8227dd1d2b1085c323..f4d1c6e130f3dd131c37f7b1ea696c7b04500173 100644
--- a/doc/istl/comm/Makefile.am
+++ b/doc/istl/comm/Makefile.am
@@ -9,6 +9,8 @@ SUFFIXES = .dvi .tex .pdf
dist_pkgdata_DATA = communication.pdf communication.ps
+#communication.dvi_DEPENDENCIES = communication.tex indexset.cc reverse.hh
+
noinst_PROGRAMS = $(MPIPROGRAMS)
indexset_SOURCES = indexset.cc
diff --git a/doc/istl/comm/buildindexset.hh b/doc/istl/comm/buildindexset.hh
new file mode 100644
index 0000000000000000000000000000000000000000..c0b612453d50fbca68e8acbe3edc8245418b924f
--- /dev/null
+++ b/doc/istl/comm/buildindexset.hh
@@ -0,0 +1,58 @@
+// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+// vi: set et ts=4 sw=2 sts=2:
+// $Id$
+#ifndef BUILDINDEXSET_HH
+#define BUILDINDEXSET_HH
+
+
+#include <dune/istl/indexset.hh>
+#include <dune/istl/plocalindex.hh>
+#include "mpi.h"
+
+/**
+ * @brief Flag for marking the indices.
+ */
+enum Flag {owner, overlap};
+
+// The type of local index we use
+typedef Dune::ParallelLocalIndex<Flag> LocalIndex;
+
+/**
+ * @brief Add indices to the example index set.
+ * @param indexSet The index set to build.
+ */
+template<class TG, int N>
+void build(Dune::IndexSet<TG,LocalIndex,N>& indexSet)
+{
+ //
+ // The number of processes
+ int size;
+ MPI_Comm_size(MPI_COMM_WORLD, &size);
+
+ // The rank of our process
+ int rank;
+ MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+ // Indicate that we add or remove indices.
+ indexSet.beginResize();
+
+ if(rank==0) {
+ indexSet.add(0, LocalIndex(0,overlap,true));
+ indexSet.add(2, LocalIndex(1,owner,true));
+ indexSet.add(6, LocalIndex(2,owner,true));
+ indexSet.add(3, LocalIndex(3,owner,true));
+ indexSet.add(5, LocalIndex(4,owner,true));
+ }
+
+ if(rank==1) {
+ indexSet.add(0, LocalIndex(0,owner,true));
+ indexSet.add(1, LocalIndex(1,owner,true));
+ indexSet.add(7, LocalIndex(2,owner,true));
+ indexSet.add(5, LocalIndex(3,overlap,true));
+ indexSet.add(4, LocalIndex(4,owner,true));
+ }
+
+ // Modification is over
+ indexSet.endResize();
+}
+#endif
diff --git a/doc/istl/comm/communication.tex b/doc/istl/comm/communication.tex
index 2a4e59312e914f2b1589e01005a99b78b1a91090..e038f54e087ff1194b1e8c0416f9ab08c03fa596 100644
--- a/doc/istl/comm/communication.tex
+++ b/doc/istl/comm/communication.tex
@@ -147,6 +147,19 @@ to be persistent. Further on we will call this global identifier
\lstinline!N! is used internally to specify the chunk size of the
array list.
+The pairs of global and local index are ordered by ascending global
+index. Thus it it possible to access the pairs via
+\lstinline!operator[](TG& global)! in $log(n)$ time, where $n$ is the
+number of pairs in the set.
+
+Due to the ordering the index set can only be changed, i.~e. indices
+added or deleted, in a special resize phase. By calling the functions
+\lstinline!beginResize()! and \lstinline!endResize()! the programmer
+indicates that the resize phase starts and ends, respectively. During
+the call of \lstinline!endResize()! the deleted indices will be
+removed and the added indices will be merged with the existing
+ones.
+
To be able to attach further information to the index the only
prerequesite for the type of the local index is that it is convertible
to \lstinline!std::size_t! as it it meant for adressing array
@@ -170,9 +183,19 @@ As the programmer often knows in advance which indices might also be
present on other processes there is the possiblity to mark the index
as public.
-Let us look at a short example on how to use the classes:
+\paragraph{Usage Examples}
+Let us look at a short example on how to build an index set:
+
+\lstinputlisting[caption=Build an Index Set,
+label=lst:build_indexset]{buildindexset.hh}
+
+Due to the complexity of \lstinline!operator[](TG& global)! it is
+always advisable to use iterators to access the index pairs of the
+set.
+The following example demonstrates their usage:
+\lstinputlisting[caption=Usage of Index Set Iterators,
+label=lst:indexset_iterator]{reverse.hh}
-\lstinputlisting[caption=build an index set, label=lst:build_indexset]{indexset.cc}
\section{Remote Indices}
\label{sec:remote-indices}
diff --git a/doc/istl/comm/indexset.cc b/doc/istl/comm/indexset.cc
index 44bf5da690b95e4879ba78e07d2e31f17e269cb5..67e9b1b10d21e1cc4d38d849b7d854d09b3ed400 100644
--- a/doc/istl/comm/indexset.cc
+++ b/doc/istl/comm/indexset.cc
@@ -5,12 +5,8 @@
#include <dune/istl/plocalindex.hh>
#include <iostream>
#include "mpi.h"
-
-/**
- * @brief Flag for marking the indices.
- */
-enum Flag {owner, overlap};
-
+#include "buildindexset.hh"
+#include "reverse.hh"
int main(int argc, char **argv)
{
@@ -20,11 +16,10 @@ int main(int argc, char **argv)
// The number of processes
int size;
+ MPI_Comm_size(MPI_COMM_WORLD, &size);
// The rank of our process
int rank;
-
- MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
// The type used as the local index
@@ -40,30 +35,22 @@ int main(int argc, char **argv)
// The index set
IndexSet indexSet;
- // Indicate that we add or remove indices.
- indexSet.beginResize();
+ build(indexSet);
- if(rank==0) {
- indexSet.add(0, LocalIndex(0,overlap,true));
- indexSet.add(2, LocalIndex(1,owner,true));
- indexSet.add(6, LocalIndex(2,owner,true));
- indexSet.add(3, LocalIndex(3,owner,true));
- indexSet.add(5, LocalIndex(4,owner,true));
- }
- if(rank==1) {
+ // Print the index set
+ std::cout<<indexSet<<std::endl;
- indexSet.add(0, LocalIndex(0,owner,true));
- indexSet.add(1, LocalIndex(1,owner,true));
- indexSet.add(7, LocalIndex(2,owner,true));
- indexSet.add(5, LocalIndex(3,overlap,true));
- indexSet.add(4, LocalIndex(4,owner,true));
- }
- // Modification is over
- indexSet.endResize();
+ reverseLocalIndex(indexSet);
// Print the index set
+ if(rank==0)
+ std::cout<<"Reordered lcoal indices:"<<std::endl;
+
+ MPI_Barrier(MPI_COMM_WORLD);
+
std::cout<<indexSet<<std::endl;
+ // Assign new local indices
// Let MPI do a cleanup
MPI_Finalize();
diff --git a/doc/istl/comm/reverse.hh b/doc/istl/comm/reverse.hh
new file mode 100644
index 0000000000000000000000000000000000000000..abe015a75c9f8d3fcaede99df29ca34ec0f5777c
--- /dev/null
+++ b/doc/istl/comm/reverse.hh
@@ -0,0 +1,40 @@
+// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+// vi: set et ts=4 sw=2 sts=2:
+// $Id$
+#ifndef REVERSE_HH
+#define REVERSE_HH
+
+#include <dune/istl/plocalindex.hh>
+#include <dune/istl/indexset.hh>
+
+/**
+ * @brief Reverse the local indices of an index set.
+ *
+ * Let the index set have N entries than the index 0 will become N-1,
+ * 1 become N-2, ..., and N-1 will become 0.
+ * @param indexSet The index set to reverse.
+ */
+template<typename TG, typename TL, int N>
+void reverseLocalIndex(Dune::IndexSet<TG,TL,N>& indexSet)
+{
+ // reverse the local indices
+ typedef typename Dune::IndexSet<TG,TL,N>::iterator iterator;
+
+ iterator end = indexSet.end();
+ size_t maxLocal = 0;
+
+ // find the maximal local index
+ for(iterator index = indexSet.begin(); index != end; ++index) {
+ // Get the local index
+ LocalIndex& local = index->local();
+ maxLocal = std::max(maxLocal, local.local());
+ }
+
+ for(iterator index = indexSet.begin(); index != end; ++index) {
+ // Get the local index
+ LocalIndex& local = index->local();
+ local = maxLocal--;
+ }
+
+}
+#endif