assert MPI_INITIALIZED returns the state we expect

[[Imported from SVN: r6227]]

dune/common/mpihelper.hh

@@ -205,13 +205,26 @@ namespace Dune
     int size_;
     void prevent_warning(int){}
 
+    static bool wasInitialized ()
+    {
+      int wasInitialized = -1;
+      MPI_Initialized( &wasInitialized );
+      return bool( wasInitialized );
+    }
+
     //! \brief calls MPI_Init with argc and argv as parameters
     MPIHelper(int& argc, char**& argv)
     {
       rank_ = -1;
       size_ = -1;
+
+      assert( !wasInitialized() );
       static int is_initialized = MPI_Init(&argc, &argv);
       prevent_warning(is_initialized);
+
+      MPI_Init(&argc, &argv);
+      assert( wasInitialized() );
+
       MPI_Comm_rank(MPI_COMM_WORLD,&rank_);
       MPI_Comm_size(MPI_COMM_WORLD,&size_);