printf("MPI_Allreduce did not return MPI_ERR_TYPE for MPI_DATATYPE_NULL type\n");
status = MPI_Allreduce(sb, rb, size, MPI_UNSIGNED_LONG_LONG, MPI_OP_NULL, MPI_COMM_WORLD);
if(status!=MPI_ERR_OP)
printf("MPI_Allreduce did not return MPI_ERR_TYPE for MPI_DATATYPE_NULL type\n");
status = MPI_Allreduce(sb, rb, size, MPI_UNSIGNED_LONG_LONG, MPI_OP_NULL, MPI_COMM_WORLD);
if(status!=MPI_ERR_OP)