[Mpi3-rma] Updated Proposal 1

Underwood, Keith D keith.d.underwood at intel.com
Wed Dec 8 10:38:52 CST 2010

> > (b) Do we know any network (except ones that emulate one-sided
> > communication over two-sided messaging) that provide strict ordering?
> As
> > far as I know, most networks only provide ordering between PUTs (or
> > atomic PUTs). Ordering between GETs is also not provided, unless the
> > user does a flush after each GET operation. Is this only for
> convenience?
> I don't know. Just that you're aware: the current default would force
> the MPI implementation to flush after each get. However, I am also
> planning to add an advice to users somewhere *very visible* that the
> user should really strive to provide these info arguments if possible
> (because the performance difference could be hideous). So the editing
> is
> not finished but 11.8.2 is ready for discussion ;-).

Yeah, I think we underspecified "partial".  Accumulate->GetAccumulate should be ordered, but GetAccumulate->Accumulate should not.  The former is trivial if we have Accumulate->Accumulate ordering already.  As an example, InfiniBand gives the former, but not the latter (unless you set the fence bit and then ugly things happen).


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