[mpiwg-rma] Atomicity and Pair Types

Balaji, Pavan balaji at anl.gov
Wed Sep 12 15:55:12 CDT 2018

Yes, correct.  Although, Nathan had a ticket at some point where he wanted to allow MPI to overwrite the padding bytes in such cases.

  -- Pavan

> On Sep 12, 2018, at 3:49 PM, Jim Dinan via mpiwg-rma <mpiwg-rma at lists.mpi-forum.org> wrote:
> Hi All,
> Sanity check --- my reading of the spec. indicates that accumulate operations performed on pair types guarantee atomicity at the level of the whole pair type.  Here are the relevant passages:
> Section 11.7.1: The outcome of concurrent accumulate operations to the same location with the same predefined datatype is as if the accumulates were done at that location in some serial order.
> Section 5.9.4: In order to use MPI_MINLOC and MPI_MAXLOC in a reduce operation, one must provide a datatype argument that represents a pair (value and index). MPI provides nine such predefined datatypes.
> Is that right?
> Thanks,
>  ~Jim.
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