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.

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&);

[Steffen Müthing]

Maybe unrelated, but what is this weird static int is_initialized doing here? If anything, we should check its value and throw an exception on error...

[Markus Blatt]

Why throw an exception when we just want to discard subequent calls to MPI_Init? But we might be overprotective here as instance should already take care of this with the static MPIHelper singleton variable.

[Christian Engwer]

Not necessarily. It might be that it is already initialized via some other part of the code. E.g. in my python code I initialize via mpi4py and thus DUNE should avoid a second initialization.