Advantages of Datatypes
Cominations of elementary datatypes into a derived user defined datatype allows clean communication of collections of disparate types in a single MPI call.
Elimination of length (in bytes) in favor of count (of items of a given type) is clearer
Specifying application-oriented layouts allows maximal use of special hardware and optimized memory use
However this wonderful technology is problematical in Java where layout of data structures in memory is not defined in most cases
- Java’s serialization subsumes user defined datatypes as a general way of packing a class of disparate types into a message that can be sent between heterogeneous computers