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

[Jed Brown]

On Mon, Apr 23, 2012 at 21:20, Rajeev Thakur <thakur at mcs.anl.gov> wrote:

> One reason is that MPI_Accumulate allows only a restricted form of derived
> datatype, where all basic elements are of the same type. In MPI_Reduce you
> can pass any crazy datatype and you get to define the reduction operation
> for that.
>

Is it somehow expensive to remember/determine that the datatype consists
only of basic types, such that MPI_Reduce can process it in the same way
that MPI_Accumulate does?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/mpich-discuss/attachments/20120423/a48025be/attachment.htm>