c++: MPI communicator as global variable

Question

I need the MPI world communicator to be accessible in functions/class member functions. But by design/convention, MPI environments and communicators are always defined and

Answer 1

I don't like global pointers in general: who's responsible for deleting them? How do you make sure the pointer is not accessed before the object is created, or after the object is destroyed?

I'd be tempted to wrap the pointer and its access in a class. (Warning: The following hasn't seen a compiler so might have all sorts of issues, and I'm not familiar with MPI)

class CMPIwrapper
{
public:
    CMPIwrapper(boost::mpi::communicator& myMPIworld):myMPIworld_(myMPIworld){}
    rank_type GetRank()const
    {
        return( my_MPI_world_ptr->rank() );
    }
private:
    boost::mpi::communicator& myMPIworld_;
};    

int main(int argc, char* argv[])
{        
    boost::mpi::environment my_boost_mpi_env(argc, argv);
    boost::mpi::communicator my_MPI_world; 
    CMPIwrapper my_MPI_wrapper(my_MPI_world);       

    my_MPI_rank = CMPIwrapper.GetRank();
}

Your own objects that used to use the pointer could work in the same way: their constructor could be passed a reference to your boost::mpi::communicator, or if the set of operations on your boost::mpi::communicator are well defined, they could be passed a reference to the wrapper.