[mpich-discuss] Persistent Communication using MPI_SEND_INIT, MPI_RECV_INIT etc.

[Jeff Hammond]

You might want to look at neighborhood collectives, which are
discussed in Chapter 7 of MPI-3.  This is a new feature so it may not
be implemented in all MPI implementations, but MPICH supports it.  I
guess MVAPICH will support it soon enough if not already.

When persistent MPI send/recv is discussed at the MPI Forum, it is
often described as an inadequate solution because it does not specify
a full channel and thus some important optimizations, e.g. for RDMA,
may not be feasible.

If you can use MPI-3 RMA, that is probably going to be a good idea,
although high-quality support for RMA varies.  MPICH-derived
implementations usually do a good job though.

Best,

Jeff

On Tue, Mar 26, 2013 at 11:25 AM, Timothy Stitt <Timothy.Stitt.9 at nd.edu> wrote:
> Hi all,
>
> I've been asking this question around various MPI boards to try and get a consensus before I decide to rewrite some MPI code. I am grateful for any advice that you can give.
>
> I've inherited a MPI code that was written ~8-10 years ago and it predominately uses MPI persistent communication routines for data transfers e.g. MPI_SEND_INIT, MPI_RECV_INIT, MPI_START etc.  (which I am not familiar with and don't normally hear much discussion about). I was just wondering if using persistent communication calls is still regarded as the most efficient/scalable way to perform communication when the communication pattern is known and fixed amongst neighborhood processes? We regularly run the code across an IB network so would there be a benefit to rewrite the code using another approach (e.g. MPI one-sided communication) or should I leave it as it is? The code currently scales up to 10K cores and I want to push it even further and thus was wondering if there is any benefit in tinkering with this persistent MPI communication approach?
>
> Thanks in advance for any advice.
>
> Tim.
>
> _______________________________________________
> discuss mailing list     discuss at mpich.org
> To manage subscription options or unsubscribe:
> https://lists.mpich.org/mailman/listinfo/discuss



-- 
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond
https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond