I do not understand the need for two distinct origin side operations if you will assume the agency infrastructure must always be standing by ready to be activated.
The MPI implementation will be able to determine at the origin side if the parameters passed into a complex RMA fit the capabilities of its NIC. It can decide whether to use the intrinsic NIC mode or the software agent mode. If it has a NIC that does integer accumulate but not floating point accumulate, the implementation can pick between NIC mode and agent mode. When a new NIC that does floating point accumulate comes along, the implementation can exploit it with no need for application rewrite.
On the other hand, the RAW RMA can be used by by applications that want to exploit NIC capabilities that are widely available today and do not want to drag in overheads for an agent waiting on the sidelines. An agent that they may know will never be needed. If someday in the future the typical NIC has certain additional capabilities we can add a richer RAW operation to the MPI standard.
Can you explain to me what you expect to have always available as a software agent that will be there at no significant cost in memory or harm to performance of non-RMA operations?
Are you thinking we need two distinct routines just to avoid a couple "if" tests to decide inside libmpi whether to use NIC based or agent based RMA?
Dick
Dick Treumann - MPI Team
IBM Systems & Technology Group
Dept X2ZA / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
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