[mpich-discuss] determinism in collectives

Jed Brown jedbrown at mcs.anl.gov
Mon Nov 12 21:40:10 CST 2012

However, the standard does contain the following (MPI-3.0 page 175)

*Advice to implementors.*
*It is strongly recommended that MPI_REDUCE be im-*
*plemented so that the same result be obtained whenever the function is
applied on*
*the same arguments, appearing in the same order. Note that this may
prevent op-*
*timizations that take advantage of the physical location of ranks. (End of
advice to*

It would be useful to have a table of which implementations adhere to this

On Mon, Nov 12, 2012 at 9:35 PM, Pavan Balaji <balaji at mcs.anl.gov> wrote:

> The MPI standard does not guarantee this.  For example, an
> implementation could use topology-aware reductions or an MPI_ANY_SOURCE
> while waiting for messages from peers making the order in which the
> reduction operations are applied different for each run.
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