<div class="gmail_quote">On Mon, Apr 23, 2012 at 20:36, Rajeev Thakur <span dir="ltr"><<a href="mailto:thakur@mcs.anl.gov">thakur@mcs.anl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
MPI_Accumulate allows you to do MPI_SUM on a derived datatype. MPI_Reduce does not. It requires you to create your own reduction operation for derived datatypes. MPI_Accumulate, on the other hand, does not allow user-defined reduction operations at all.<br>
</blockquote><div><br></div><div>Right, but why is it this way? What was the rationale for not having the same extended capability of predefined operations (a la MPI_Accumulate) apply to reductions? It's obnoxious when exposing a common API that may be implemented in terms of one-sided or collectives.</div>
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