}intmain(intargc,char*argv[]) {intierr;ierr=MPI_Init(&argc,&argv);CHECK_MPI(ierr);constMPI_Commcommunicator=MPI_COMM_WORLD;constintkey=(this_mpi_process(communicator)==1?0:1);MPI_Commsub_comm;ierr=MPI_Comm_split_type(communicator,MPI_COMM_TYPE_SHARED,key,MPI_INFO_NULL, _comm);CHECK...