Add Utilities::System::calculate_collective_mpi_sum.

git-svn-id: https://svn.dealii.org/trunk@24412 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/doc/news/changes.h b/deal.II/doc/news/changes.h
index 4e4246bfdfd248b0439af0100e6ab7556fb38222..4d059b040f71e7136d7cb794507c641f59f8816c 100644 (file)
--- a/deal.II/doc/news/changes.h
+++ b/deal.II/doc/news/changes.h
@@ -297,6 +297,12 @@ 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
+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>
+(Wolfgang Bangerth, 2011/09/25)
+
 <li> New: The CellAccessor::is_locally_owned function is a shortcut
 for the <code>!cell-@>is_ghost() && !cell-@>is_artificial()</code> pattern
 found in many places when dealing with distributed meshes.

diff --git a/deal.II/include/deal.II/base/utilities.h b/deal.II/include/deal.II/base/utilities.h
index 7a821167276f09c8461961d11b7ca461cebe0a3f..e3f08d2ffc660fd92d1d6d9a6968c10c71106234 100644 (file)
--- a/deal.II/include/deal.II/base/utilities.h
+++ b/deal.II/include/deal.II/base/utilities.h
@@ -23,7 +23,8 @@
 #if defined(DEAL_II_COMPILER_SUPPORTS_MPI) || defined(DEAL_II_USE_PETSC)
 #include <mpi.h>
 #else
-typedef int MPI_Comm;
+
+extern boost::mutex m;typedef int MPI_Comm;
 #endif
 
 #ifdef DEAL_II_USE_TRILINOS
@@ -439,6 +440,22 @@ 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
@@ -862,6 +879,58 @@ namespace Utilities
          len = half;
       }
   }
+  
+  
+  namespace System
+  {
+    namespace internal
+    {
+#ifdef DEAL_II_COMPILER_SUPPORTS_MPI      
+      /**
+       * Return the corresponding MPI data type id for the argument given.
+       */
+      inline MPI_Datatype mpi_type_id (const int *)
+      {
+       return MPI_INT;
+      }
+
+      
+      inline MPI_Datatype mpi_type_id (const unsigned int *)
+      {
+       return MPI_UNSIGNED;
+      }
+
+
+      inline MPI_Datatype mpi_type_id (const float *)
+      {
+       return MPI_FLOAT;
+      }
+
+
+      inline MPI_Datatype mpi_type_id (const double *)
+      {
+       return MPI_DOUBLE;
+      }
+#endif
+    }
+    
+    template <typename T>
+    inline
+    T calculate_collective_mpi_sum (const T &t,
+                                   const MPI_Comm &mpi_communicator)
+    {
+#ifdef DEAL_II_COMPILER_SUPPORTS_MPI
+      T sum;
+      MPI_Allreduce (const_cast<void*>(static_cast<const void*>(&t)),
+                    &sum, 1, internal::mpi_type_id(&t), MPI_SUM, 
+                    mpi_communicator);
+      return sum;
+#else
+      (void)mpi_communicator;
+      return t;
+#endif
+    }
+  }
 }
 
 

diff --git a/tests/mpi/collective_02.cc b/tests/mpi/collective_02.cc
new file mode 100644 (file)
index 0000000..1948f04
--- /dev/null
+++ b/tests/mpi/collective_02.cc
@@ -0,0 +1,74 @@
+//---------------------------------------------------------------------------
+//    $Id$
+//    Version: $Name$
+//
+//    Copyright (C) 2009, 2010, 2011 by the deal.II authors
+//
+//    This file is subject to QPL and may not be  distributed
+//    without copyright and license information. Please refer
+//    to the file deal.II/doc/license.html for the  text  and
+//    further information on this license.
+//
+//---------------------------------------------------------------------------
+
+
+// check Utilities::System::calculate_collective_mpi_sum()
+
+#include "../tests.h"
+#include <deal.II/base/logstream.h>
+#include <deal.II/base/utilities.h>
+#include <fstream>
+
+void test()
+{
+  unsigned int myid = Utilities::System::get_this_mpi_process (MPI_COMM_WORLD);
+  const unsigned int numprocs = Utilities::System::get_n_mpi_processes (MPI_COMM_WORLD);
+
+  int int_sum, uint_sum, double_sum, float_sum;
+  int_sum
+    =
+    Utilities::System::calculate_collective_mpi_sum<int>(myid,
+                                                        MPI_COMM_WORLD);
+  uint_sum
+    =
+    Utilities::System::calculate_collective_mpi_sum<unsigned int>(myid,
+                                                                 MPI_COMM_WORLD);
+  float_sum
+    =
+    Utilities::System::calculate_collective_mpi_sum<float>(myid,
+                                                          MPI_COMM_WORLD);
+  double_sum
+    =
+    Utilities::System::calculate_collective_mpi_sum<double>(myid,
+                                                           MPI_COMM_WORLD);
+
+  if (myid==0)
+    deallog << int_sum << ' ' << uint_sum << ' ' << double_sum << ' ' << float_sum << std::endl;
+}
+
+
+int main(int argc, char *argv[])
+{
+#ifdef DEAL_II_COMPILER_SUPPORTS_MPI
+  Utilities::System::MPI_InitFinalize mpi (argc, argv);
+#else
+  (void)argc;
+  (void)argv;
+  compile_time_error;
+
+#endif
+
+  if (Utilities::System::get_this_mpi_process (MPI_COMM_WORLD) == 0)
+    {
+      std::ofstream logfile(output_file_for_mpi("collective_02").c_str());
+      deallog.attach(logfile);
+      deallog.depth_console(0);
+      deallog.threshold_double(1.e-10);
+
+      deallog.push("mpi");
+      test();
+      deallog.pop();
+    }
+  else
+    test();
+}

diff --git a/tests/mpi/collective_02/ncpu_1/cmp/generic b/tests/mpi/collective_02/ncpu_1/cmp/generic
new file mode 100644 (file)
index 0000000..a3848dd
--- /dev/null
+++ b/tests/mpi/collective_02/ncpu_1/cmp/generic
@@ -0,0 +1,6 @@
+
+DEAL:mpi::Running on 1 CPU(s).
+DEAL:mpi::sum: 0 avg: 0 min: 0 @0 max: 0 @0
+DEAL:mpi::sum: 1.00000 avg: 1.00000 min: 1.00000 @0 max: 1.00000 @0
+DEAL:mpi::sum: 1.00000 avg: 1.00000 min: 1.00000 @0 max: 1.00000 @0
+DEAL:mpi::done

diff --git a/tests/mpi/collective_02/ncpu_10/cmp/generic b/tests/mpi/collective_02/ncpu_10/cmp/generic
new file mode 100644 (file)
index 0000000..8e5a42c
--- /dev/null
+++ b/tests/mpi/collective_02/ncpu_10/cmp/generic
@@ -0,0 +1,2 @@
+
+DEAL:mpi::45 45 45 45

diff --git a/tests/mpi/collective_02/ncpu_4/cmp/generic b/tests/mpi/collective_02/ncpu_4/cmp/generic
new file mode 100644 (file)
index 0000000..58299a0
--- /dev/null
+++ b/tests/mpi/collective_02/ncpu_4/cmp/generic
@@ -0,0 +1,2 @@
+
+DEAL:mpi::6 6 6 6