Merge branch 'feature/fix-call-MPIfinalize-onlyif-MPIInit-called' into 'master'

MPIHelper should only finalize MPI if it called init

MPIHelper only calls MPI if it was not already called before MPIHelper is constructed. Finalize is however always called on destruction leading to
problems with other packages calling init/finalize before/after MPIHelper
is setup. Added a bool storing the information if MPIInit was called by the
MPIHelper so that finalize is only called in that case.

See merge request !58

dune/common/parallel/mpihelper.hh

@@ -233,10 +233,12 @@ namespace Dune
   private:
     int rank_;
     int size_;
+    bool initializedHere_;
     void prevent_warning(int){}
 
     //! \brief calls MPI_Init with argc and argv as parameters
     MPIHelper(int& argc, char**& argv)
+    : initializedHere_(false)
     {
       int wasInitialized = -1;
       MPI_Initialized( &wasInitialized );
@@ -246,6 +248,7 @@ namespace Dune
         size_ = -1;
         static int is_initialized = MPI_Init(&argc, &argv);
         prevent_warning(is_initialized);
+        initializedHere_ = true;
       }
 
       MPI_Comm_rank(MPI_COMM_WORLD,&rank_);
@@ -261,10 +264,11 @@ namespace Dune
     {
       int wasFinalized = -1;
       MPI_Finalized( &wasFinalized );
-      if(!wasFinalized) {
-      MPI_Finalize();
-      dverb << "Called MPI_Finalize on p=" << rank_ << "!" <<std::endl;
-    }
+      if(!wasFinalized && initializedHere_)
+      {
+        MPI_Finalize();
+        dverb << "Called MPI_Finalize on p=" << rank_ << "!" <<std::endl;
+      }
 
     }
     MPIHelper(const MPIHelper&);