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

implementors.)

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

On Mon, Nov 12, 2012 at 9:35 PM, Pavan Balaji <balaji@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.