[mpich-discuss] Why do predefined MPI_Ops function elementwise in MPI_Accumulate, but not in MPI-1 routines?

[Jed Brown]

On Tue, Apr 24, 2012 at 15:36, William Gropp <wgropp at illinois.edu> wrote:

> A lot of this had to do with wanting to make it possible for
> MPI_Accumulate to be executed entirely in hardware, respecting the various
> MPI one-sided operations and semantics, including the atomicity rules, and
> not requiring the execution of arbitrary user code.  This was not a concern
> for Reduce/Allreduce/Scan/Exscan/Reduce_scatter.
>

Would it have been that problematic to run the built-in operations in
hardware and do the others in software?
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