Shouldn't it just be a trivial request -- why map to null ? - shortcut should of course happen internally but the request should be valid --- undesirable side effects possible Imho with a literal mapping ! Anthony Skjellum, PhD 205-807-4968

On Dec 11, 2014, at 3:30 PM, Jeff Hammond <[email protected]> wrote:

I would hope that the Ianything is matched with a corresponding Test/Wait* call on every process that calls it. To allow otherwise seems pretty odd.

Presumably, if Ibcast is a no-op when root=MPI_PROC_NULL, then the request can be set to MPI_REQUEST_NULL and thus completing it is trivial.

If the standard says that completing a request known to be MPI_REQUEST_NULL is not required, then I suppose the user can avoid making the completion call, but I don't like that style.

Jeff

...

On Thu, Dec 11, 2014 at 11:30 AM, Fab Tillier <[email protected]> wrote: Hi Folks,

I can’t find anything in the standard document that explains the behavior for NBC requests on intercommunicators when root == MPI_PROC_NULL. Taking MPI_Ibcast as an example, what is the output value of request? Is it MPI_REQUEST_NULL? Is it not set at all? Is it a valid request that must be completed?

Thanks,

-Fab

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