Dear Benjamin, as far as I understand the MPI standard, RMA operations non-blocking in the sense that you need to complete them with a separate call (flush/unlock/...).
I cannot find the place in the standard right now, but I think an implementation is allowed to either buffer RMA requests or block until the RMA operation can be initiated, and the user should not assume either. I have seen the one and the other behavior across implementations in the past. For your second question, yes, flush is supposed to block until remote completion of the operation. That said, I think to recall that Open-MPI 1.x did not support asynchronous target-side progress for passive-target synchronization (which is used in your benchmark example), so the behavior you observed is to some extent expected. Cheers, Marc-Andre On 04.05.2017 01:25, Benjamin Brock wrote: > MPI_Accumulate() is meant to be non-blocking, and MPI will block until > completion when an MPI_Win_flush() is called, correct? > > In this (https://hastebin.com/raw/iwakacadey) microbenchmark, > MPI_Accumulate() seems to be blocking for me in OpenMPI 1.10.6. > > I'm seeing timings like > > [brock@nid00622 junk]$ mpirun -n 4 ./junk > Write: 0.499229 rq, 0.000018 fl; Read: 0.463764 rq, 0.000035 fl > Write: 0.464914 rq, 0.000012 fl; Read: 0.419703 rq, 0.000024 fl > Write: 0.499686 rq, 0.000014 fl; Read: 0.422557 rq, 0.000023 fl > Write: 0.437960 rq, 0.000015 fl; Read: 0.396530 rq, 0.000023 fl > > Meaning up to half a second is being spent issuing requests, but > almost no time is spent in flushes. The time spent in requests scales > with the size of the messages, but the time spent in flushes stays the > same. > > I'm compiling this with mpicxx acc.cpp -o acc -std=gnu++11 -O3. > > Any suggestions? Am I using this incorrectly? > > Ben > > > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://rfd.newmexicoconsortium.org/mailman/listinfo/users > -- Marc-Andre Hermanns Jülich Aachen Research Alliance, High Performance Computing (JARA-HPC) Jülich Supercomputing Centre (JSC) Wilhelm-Johnen-Str. 52425 Jülich Germany Phone: +49 2461 61 2509 | +49 241 80 24381 Fax: +49 2461 80 6 99753 www.jara.org/jara-hpc email: m.a.herma...@fz-juelich.de
smime.p7s
Description: S/MIME Cryptographic Signature
_______________________________________________ users mailing list users@lists.open-mpi.org https://rfd.newmexicoconsortium.org/mailman/listinfo/users
