public static unsafe extern int MPI_Op_free(ref MPI_Op op);
public static unsafe extern int MPI_Scan(IntPtr sendbuf, IntPtr recvbuf, int count, MPI_Datatype datatype, MPI_Op op, MPI_Comm comm);
public static unsafe extern int MPI_Op_create(MPI_User_function function, int commute, out MPI_Op op);
public static unsafe extern int MPI_Reduce_scatter(IntPtr sendbuf, IntPtr recvbuf, int[] recvcounts, MPI_Datatype datatype, MPI_Op op, MPI_Comm comm);