(j3.2006) (SC22WG5.4946) AW: WG5 ballot on first draft TS 18508, Additional Parallel Features in Fortran (Update)

Bill Long longb
Fri Mar 29 19:09:23 EDT 2013

On 3/29/13 5:49 AM, Bader, Reinhold wrote:
> (D.1) Add CO_MULT for efficiency
> Nowadays interconnects have support for offloading certain operations
> to the infrastructure (e.g., FCA aka "fabric collective acceleration"),
> thereby considerably improving performance.
> However, it appears unlikely that the relatively general CO_REDUCE
> facility would be able to support this facility. Therefore, it may
> be desirable to also provide a CO_MULT collective for arguments of
> numeric type that supports multiplicative reductions, in order to
> obtain the same level of performance for all basic numeric operations.

If we added this, it would be CO_PRODUCT since the local one is PRODUCT. 
  The previous proposal had CO_PRODUCT.  It was removed because the 
corresponding MPI_REDUCE for that operation almost never occurs in real 
codes.   Is there any common usage of this operation?   Also, is there 
hardware support in network hardware for a multiply reduction?


Bill Long                                           longb at cray.com
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