[mpich-discuss] MPI_WIN_FENCE versus MPI_WIN_{LOCK|UNLOCK}

[Jim Dinan]

Strictly MPI-2, no MPI-3 stuff.

  ~Jim.

On 6/1/12 3:10 PM, Jed Brown wrote:
> On Fri, Jun 1, 2012 at 2:30 PM, Jim Dinan <dinan at mcs.anl.gov
> <mailto:dinan at mcs.anl.gov>> wrote:
>
>     That's a good point, and you can also use MPI_Win_test instead of
>     wait to avoid blocking.  IIRC, this is still slightly more
>     synchronizing than passive mode if you have multiple readers/writers
>     in the active mode epoch.  All processes that access the window
>     during the exposure epoch will need to be specified in the group
>     argument to post/start and wait/test will need to also ensure that
>     all processes in that group have called complete.  So, if you can
>     use intermediate data from the writers, passive mode will give you
>     more concurrency.
>
>
> Are you talking about MPI-2 passive mode or MPI-3 stuff like
> request-based RMA?
>
> I see how MPI_Put is less synchronous with passive mode (although
> synchronization through some other channel is normally necessary for the
> target to know when some group of incoming writes have completed), but
> MPI_Get looks much more synchronous in passive mode (especially with
> MPI-2 semantics where only one target window can be accessed during a
> lock/unlock epoch). MPI_Rget seems to help with this.
>
>
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