From 08c9101ee9b0977b930517f4fb15c7e34262e975 Mon Sep 17 00:00:00 2001
From: bangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Mon, 26 Sep 2011 12:02:41 +0000
Subject: [PATCH] Implement the new function in namespace Utilities::MPI
 instead. Give it a simpler name.

git-svn-id: https://svn.dealii.org/trunk@24416 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/doc/news/changes.h               |  2 +-
 deal.II/include/deal.II/base/utilities.h | 51 ++++++++++++++----------
 tests/mpi/collective_02.cc               | 16 ++++----
 3 files changed, 40 insertions(+), 29 deletions(-)

diff --git a/deal.II/doc/news/changes.h b/deal.II/doc/news/changes.h
index 4d059b040f..9abc392900 100644
--- a/deal.II/doc/news/changes.h
+++ b/deal.II/doc/news/changes.h
@@ -297,7 +297,7 @@ and DoF handlers embedded in higher dimensional space have been added.
 <h3>Specific improvements</h3>
 
 <ol>
-<li> New: The function Utilities::System::calculate_collective_mpi_sum
+<li> New: The function Utilities::MPI::sum
 function can be used to compute the sum of values over a number of
 MPI processes without having to deal with the underlying MPI functions.
 <br>
diff --git a/deal.II/include/deal.II/base/utilities.h b/deal.II/include/deal.II/base/utilities.h
index e3f08d2ffc..d268d61942 100644
--- a/deal.II/include/deal.II/base/utilities.h
+++ b/deal.II/include/deal.II/base/utilities.h
@@ -274,6 +274,34 @@ namespace Utilities
   std::vector<unsigned int>
   invert_permutation (const std::vector<unsigned int> &permutation);
 
+                                   /**
+                                    * A namespace for utility functions that
+                                    * abstract certain operations using the
+				    * Message Passing Interface (MPI) or
+				    * provide fallback operations in
+				    * case deal.II is configured not to use
+				    * MPI at all.
+                                    *
+                                    * @ingroup utilities
+                                    */
+  namespace MPI
+  {    
+    /**
+     * Return the sum over all processors of the value @p t. This function
+     * is collective over all processors given in the communicator. If
+     * deal.II is not configured for use of MPI, this function simply
+     * returns the value of @p t. This function corresponds to the
+     * <code>MPI_Allreduce</code> function, i.e. all processors receive
+     * the result of this operation.
+     * 
+     * @note This function is only implemented for certain template
+     * arguments <code>T</code>, namely <code>float, double, int, 
+     * unsigned int</code>.
+     */
+    template <typename T>
+    T sum (const T &t,
+	   const MPI_Comm &mpi_communicator);
+  }
                                    /**
                                     * A namespace for utility functions that
                                     * probe system properties.
@@ -440,23 +468,6 @@ namespace Utilities
 				      */
     MPI_Comm duplicate_communicator (const MPI_Comm &mpi_communicator);
 
-    
-    /**
-     * Return the sum over all processors of the value @p t. This function
-     * is collective over all processors given in the communicator. If
-     * deal.II is not configured for use of MPI, this function simply
-     * returns the value of @p t. This function corresponds to the
-     * <code>MPI_Allreduce</code> function, i.e. all processors receive
-     * the result of this operation.
-     * 
-     * @note This function is only implemented for certain template
-     * arguments <code>T</code>, namely <code>float, double, int, 
-     * unsigned int</code>.
-     */
-    template <typename T>
-    T calculate_collective_mpi_sum (const T &t,
-				    const MPI_Comm &mpi_communicator);
-
 				     /**
 				      * Data structure to store the result of
 				      * calculate_collective_mpi_min_max_avg.
@@ -881,7 +892,7 @@ namespace Utilities
   }
   
   
-  namespace System
+  namespace MPI
   {
     namespace internal
     {
@@ -916,8 +927,8 @@ namespace Utilities
     
     template <typename T>
     inline
-    T calculate_collective_mpi_sum (const T &t,
-				    const MPI_Comm &mpi_communicator)
+    T sum (const T &t,
+	   const MPI_Comm &mpi_communicator)
     {
 #ifdef DEAL_II_COMPILER_SUPPORTS_MPI
       T sum;
diff --git a/tests/mpi/collective_02.cc b/tests/mpi/collective_02.cc
index 386b1be0ae..a0e97f1983 100644
--- a/tests/mpi/collective_02.cc
+++ b/tests/mpi/collective_02.cc
@@ -27,20 +27,20 @@ void test()
   int int_sum, uint_sum, double_sum, float_sum;
   int_sum
     =
-    Utilities::System::calculate_collective_mpi_sum<int>(myid+1,
-							 MPI_COMM_WORLD);
+    Utilities::MPI::sum<int>(myid+1,
+			     MPI_COMM_WORLD);
   uint_sum
     =
-    Utilities::System::calculate_collective_mpi_sum<unsigned int>(myid+1,
-								  MPI_COMM_WORLD);
+    Utilities::MPI::sum<unsigned int>(myid+1,
+				      MPI_COMM_WORLD);
   float_sum
     =
-    Utilities::System::calculate_collective_mpi_sum<float>(myid+1,
-							   MPI_COMM_WORLD);
+    Utilities::MPI::sum<float>(myid+1,
+			       MPI_COMM_WORLD);
   double_sum
     =
-    Utilities::System::calculate_collective_mpi_sum<double>(myid+1,
-							    MPI_COMM_WORLD);
+    Utilities::MPI::sum<double>(myid+1,
+				MPI_COMM_WORLD);
 
   if (myid==0)
     deallog << int_sum << ' ' << uint_sum << ' ' << double_sum << ' ' << float_sum << std::endl;
-- 
2.39.5