[Mpi3-subsetting] agenda for subsetting kickoff telecon ww09

[Richard Graham]

Getting rid of the data types is not an option, in my opinion.  I would be
ok if we decided on a subset that includes something that includes basic
data types and some sort of regular patterns based on these - which I
believe represents a very large fraction of the application uses.

I am NOT advocating going away from the general support we have for data
types in MPI, just providing a way for implementers to know that under some
use case scenarios (which I think are by far the common case) simpler and
more efficient data type support can be provided.  This also allows for
implementations, if they choose to take advantage of h/w gather/scatter
capabilities.  At this stage the notion of subsetting is just that - a
notion - and I don't think that as a group we have thought through all the
implications.

Rich

On 2/29/08 10:02 AM, "Torsten Hoefler" <htor_at_[hidden]> wrote:

> 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