Why Datatypes?

Since all data is labeled by type, an MPI implementation can support communication between processes on machines with very different memory representations and lengths of elementary datatypes (heterogeneous communication).
Specifying application-oriented layout of data in memory
- reduces memory-to-memory copies in the implementation
- allows the use of special hardware (scatter/gather) when available

Since all data is labeled by type, an MPI implementation can support communication between processes on machines with very different memory representations and lengths of elementary datatypes (heterogeneous communication).