My understanding has always been that MPI_Accumulate was and is atomic at granularity of the underlying built-in datatype, as opposed to byte-wise atomic like MPI_Put. This is the whole reason that MPI_Accumulate w/ MPI_REPLACE exists. Without the additional atomicity guarantee, that feature would be pointless. Jeff On Tue, Oct 2, 2012 at 11:38 AM, Richard Graham <[email protected]> wrote:

resending

From: Richard Graham Sent: Tuesday, October 02, 2012 12:22 PM To: MPI 3.0 Remote Memory Access working group ([email protected]) Subject: MPI_Accumulate

What are the requirements placed on MPI_Accumulate if more than one mpi process tries to update the same location ? Does MPI provide any consistency promises, or is it up to the application to guarantee these ? I see that the get accumulate routines are defined to be atomic, but don�t see the same requirement for accumulate.

Thanks,

Rich

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