Bronis, for the record: I do *not* advocate to get rid of datatypes! I think datatypes are a great thing for some parallel applications and they certainly should be used as a high-level abstraction. I've implemented scatter/gather list-based optimizations for modern NICs (IB). But on the other hand, there are many codes out there that do just not use datatypes. Codes that are only supposed to run in heterogeneous environments. Codes that use sockets instead of MPI. If we want to aim at this market, we need to simplify here. A simplification could be to use MPI_BYTE by default ;) but it would be better to get rid of the code and control-path overhead. Just to clarify my opinion, Torsten -- bash$ :(){ :|:&};: --------------------- http://www.unixer.de/ ----- Indiana University | http://www.indiana.edu Open Systems Lab | http://osl.iu.edu/ 150 S. Woodlawn Ave. | Bloomington, IN, 474045-7104 | USA Lindley Hall Room 135 | +01 (812) 855-3608