int clone(MPI_Datatype* type) override;
void serialize(const void* noncontiguous, void* contiguous, int count) override;
void unserialize(const void* contiguous_vector, void* noncontiguous_vector, int count, MPI_Op op) override;
int clone(MPI_Datatype* type) override;
void serialize(const void* noncontiguous, void* contiguous, int count) override;
void unserialize(const void* contiguous_vector, void* noncontiguous_vector, int count, MPI_Op op) override;