From 3f3e21039071b64385bed541437999ed949284e2 Mon Sep 17 00:00:00 2001
From: Martin Nolte <mnolte@dune-project.org>
Date: Sun, 26 Aug 2012 17:25:26 +0000
Subject: [PATCH] implement scan and partualSum (MPI_SCAN)
[[Imported from SVN: r6929]]
---
.../parallel/collectivecommunication.hh | 41 ++++++++++++++++---
.../parallel/mpicollectivecommunication.hh | 17 ++++++++
2 files changed, 53 insertions(+), 5 deletions(-)
diff --git a/dune/common/parallel/collectivecommunication.hh b/dune/common/parallel/collectivecommunication.hh
index 8c819b9ce..48f74d9a0 100644
--- a/dune/common/parallel/collectivecommunication.hh
+++ b/dune/common/parallel/collectivecommunication.hh
@@ -252,20 +252,51 @@ namespace Dune
* in every process.
*
* The template parameter BinaryFunction is the type of
- * the binary function to use for the computation
+ * the binary function to use for the computation.
*
* @param in The array to compute on.
* @param out The array to store the results in.
* @param len The number of components in the array
*/
template<typename BinaryFunction, typename Type>
- void allreduce(Type* in, Type* out, int len) const
+ int allreduce(Type* in, Type* out, int len) const
{
std::copy(in, in+len, out);
- return;
+ return 0;
}
+ /** \brief perform a partial reduction of processes 0, ..., rank
+ *
+ * The template parameter BinaryFunction gives the type of the reduction.
+ *
+ * Note: scan and allreduce are very similar. The only difference is that
+ * scan only returns the reduction of the arguments over processes
+ * 0, ..., rank instead of over all processes.
+ *
+ * \param[in] in array of input arguments
+ * \param[out] out array to store the output in
+ * \param[in] len number of elements in each array
+ */
+ template< class BinaryFunction, class T >
+ int scan ( T *in, T *out, int len ) const
+ {
+ std::copy( in, in+len, out );
+ return 0;
+ }
+
+ /** \brief compute the sum of the argument over processes 0, ..., rank
+ *
+ * Note: This function assumes that type T has an operator+
+ *
+ * \param[in] in argument for this process
+ */
+ template< class T >
+ T partialSum ( T &in ) const
+ {
+ return in;
+ }
};
-}
-#endif
+} // namespace Dune
+
+#endif // #ifndef DUNE_COLLECTIVECOMMUNICATION_HH
diff --git a/dune/common/parallel/mpicollectivecommunication.hh b/dune/common/parallel/mpicollectivecommunication.hh
index c94796cb1..fc8d278f7 100644
--- a/dune/common/parallel/mpicollectivecommunication.hh
+++ b/dune/common/parallel/mpicollectivecommunication.hh
@@ -295,6 +295,23 @@ namespace Dune
(Generic_MPI_Op<Type, BinaryFunction>::get()),communicator);
}
+ /** \copydoc CollectiveCommunication::scan(T *in,T *out,int len) const */
+ template< class BinaryFunction, class T >
+ int scan ( T *in, T *out, int len ) const
+ {
+ return MPI_Scan( in, out, len, MPITraits< T >::getType(),
+ (Generic_MPI_Op< T, BinaryFunction >::get()), communicator );
+ }
+
+ /** \copydoc CollectiveCommunication::partialSum(T &in) const */
+ template< class T >
+ T partialSum ( T &in ) const
+ {
+ T out;
+ scan< std::plus< T > >( &in, &out, 1 );
+ return out;
+ }
+
private:
MPI_Comm communicator;
int me;
--
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