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May iI open and assign to you preliminarily for at least the background and issue discussion (from emails) if not the solution?</div>
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You are welcome to pose the solution too, but you know, that's not required to get us started
<span id="π">π</span></div>
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<p style="margin-top: 0px; margin-bottom: 0px;">Anthony Skjellum, PhD</p>
<p style="margin-top: 0px; margin-bottom: 0px;">Professor of Computer Science and Chair of Excellence</p>
<p style="margin-top: 0px; margin-bottom: 0px;">Director, SimCenter</p>
<p style="margin-top: 0px; margin-bottom: 0px;">University of Tennessee at Chattanooga (UTC)</p>
<p style="margin-top: 0px; margin-bottom: 0px;">tony-skjellum@utc.edu [or skjellum@gmail.com]</p>
<p style="margin-top: 0px; margin-bottom: 0px;">cell: 205-807-4968</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> mpi-forum <mpi-forum-bounces@lists.mpi-forum.org> on behalf of Rolf Rabenseifner via mpi-forum <mpi-forum@lists.mpi-forum.org><br>
<b>Sent:</b> Saturday, September 28, 2019 3:53 AM<br>
<b>To:</b> Anthony Skjellum <skjellum@auburn.edu><br>
<b>Cc:</b> Rolf Rabenseifner <rabenseifner@hlrs.de>; Main MPI Forum mailing list <mpi-forum@lists.mpi-forum.org>; Simone Chiocchetti <simone.chiocchetti@unitn.it>; MPI-3 Collective Subgroup Discussions <mpiwg-coll@lists.mpi-forum.org><br>
<b>Subject:</b> Re: [Mpi-forum] Error/gap in MPI_NEIGHBOR_ALLTOALL/ALLGATHER</font>
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<div class="PlainText">Yes, if after seven years of MPI_NEIGHBOR_ALLTOALL, neither the user know whether their MPI library is wrong nor all implementors are sure how to implement this routine for 1 or 2 processes in cyclic Cartesian direction, then some wording
is missing in the MPI standard.<br>
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Best regards<br>
Rolf<br>
<br>
----- Anthony Skjellum <skjellum@auburn.edu> wrote:<br>
> Rolf letβs open a Ticket <br>
> <br>
> Anthony Skjellum, PhD<br>
> 205-807-4968<br>
> <br>
> <br>
> > On Sep 27, 2019, at 6:09 PM, Rolf Rabenseifner via mpi-forum <mpi-forum@lists.mpi-forum.org> wrote:<br>
> > <br>
> > Dear MPI collective WG,<br>
> > <br>
> > you may try to resolve the problem with a maybe wrong <br>
> > MPI specification for MPI_NEIGHBOR_ALLTOALL/ALLGATHER<br>
> > <br>
> > Dear MPI Forum member,<br>
> > <br>
> > you may own/use an MPI implementation that implements<br>
> > MPI_NEIGHBOR_ALLTOALL/ALLGATHER<br>
> > with race conditions if #nprocs in one dimension is<br>
> > only 1 or 2 and periodic==true<br>
> > <br>
> > The problem was reported as a bug of the OpenMPI library <br>
> > by Simone Chiochetti from DICAM at the University of Trento, <br>
> > but seems to be a bug in the MPI specification,<br>
> > or at least an advice to implementors is missing.<br>
> > <br>
> > I produced a set of animated slides.<br>
> > Please look at them in presentation mode with animation.<br>
> > <br>
> > Have fun with a problem that clearly prevents the use<br>
> > of MPI_NEIGHBOR_... routines with cyclic boundary condition<br>
> > if one wants to verify that mpirun -np 1 is doing<br>
> > the same as the sequential code.<br>
> > <br>
> > Best regards<br>
> > Rolf<br>
> > <br>
> > -- <br>
> > Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner@hlrs.de .<br>
> > High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .<br>
> > University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .<br>
> > Head of Dpmt Parallel Computing . . . <a href="http://www.hlrs.de/people/rabenseifner">
www.hlrs.de/people/rabenseifner</a> .<br>
> > Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .<br>
> > <neighbor_mpi-3_bug.pptx><br>
> > _______________________________________________<br>
> > mpi-forum mailing list<br>
> > mpi-forum@lists.mpi-forum.org<br>
> > <a href="https://lists.mpi-forum.org/mailman/listinfo/mpi-forum">https://lists.mpi-forum.org/mailman/listinfo/mpi-forum</a><br>
<br>
-- <br>
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner@hlrs.de .<br>
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .<br>
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .<br>
Head of Dpmt Parallel Computing . . . <a href="http://www.hlrs.de/people/rabenseifner">
www.hlrs.de/people/rabenseifner</a> .<br>
Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .<br>
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