A singleton will indeed have an extra thread, but it should be quiescent. I’ll check the 1.10.2 release candidate and see if it still exhibits that behavior.
> On Jan 7, 2016, at 9:32 PM, Au Eelis <auee...@gmail.com> wrote: > > Hi! > > It is in so far related, that one of these threads is actually doing > something. > > Btw, I noticed this on two separate machines! A computing cluster with > admin-built openmpi and Archlinux with openmpi from the repositories. > > However, running the code with openmpi 1.6.2 and ifort 13.0.0 does not show > this behaviour. > > Best regards, > Stefan > > > > On 01/07/2016 03:27 PM, Sasso, John (GE Power, Non-GE) wrote: >> Stefan, I don't know if this is related to your issue, but FYI... >> >> >>> Those are async progress threads - they block unless something requires >>> doing >>> >>> >>>> On Apr 15, 2015, at 8:36 AM, Sasso, John (GE Power & Water, Non-GE) >>>> <john1.sa...@ge.com> wrote: >>>> >>>> I stumbled upon something while using 'ps -eFL' to view threads of >>>> processes, and Google searches have failed to answer my question. This >>>> question holds for OpenMPI 1.6.x and even OpenMPI 1.4.x. >> >> >>>> For a program which is pure MPI (built and run using OpenMPI) and does not >>>> implement Pthreads or OpenMP, why is it that each MPI task appears as >>>> having 3 threads: >> >> >>>> UID PID PPID LWP C NLWP SZ RSS PSR STIME TTY TIME >>>> CMD >>>> sasso 20512 20493 20512 99 3 187849 582420 14 11:01 ? 00:26:37 >>>> /home/sasso/mpi_example.exe >>>> sasso 20512 20493 20588 0 3 187849 582420 11 11:01 ? 00:00:00 >>>> /home/sasso/mpi_example.exe >>>> sasso 20512 20493 20599 0 3 187849 582420 12 11:01 ? 00:00:00 >>>> /home/sasso/mpi_example.exe >> >> >>>> whereas if I compile and run a non-MPI program, 'ps -eFL' shows it running >>>> as a single thread? >>>> >>>> Granted the CPU utilization (C) for 2 of the 3 threads is zero, but the >>>> threads are bound to different processors (11,12,14). I am curious as to >>>> why this is, and no complaining that there is a problem. Thanks! >> >> >>>> --john >> >> >> -----Original Message----- >> From: users [mailto:users-boun...@open-mpi.org] On Behalf Of Au Eelis >> Sent: Thursday, January 07, 2016 7:10 AM >> To: us...@open-mpi.org >> Subject: [OMPI users] Singleton process spawns additional thread >> >> Hi! >> >> I have a weird problem with executing a singleton OpenMPI program, where an >> additional thread causes full load, while the master thread performs the >> actual calculations. >> >> In contrast, executing "mpirun -np 1 [executable]" performs the same >> calculation at the same speed but the additional thread is idling. >> >> In my understanding, both calculations should behave in the same way (i.e., >> one working thread) for a program which is simply moving some data around >> (mainly some MPI_BCAST and MPI_GATHER commands). >> >> I could observe this behaviour in OpenMPI 1.10.1 with ifort 16.0.1 and >> gfortran 5.3.0. I could create a minimal working example, which is appended >> to this mail. >> >> Am I missing something? >> >> Best regards, >> Stefan >> >> ----- >> >> MWE: Compile this with "mpifort main.f90". When executing with "./a.out", >> there is thread wasting cycles, while the master thread waits for input. >> When executing with "mpirun -np 1 ./a.out" this thread is idling. >> >> program main >> use mpi_f08 >> implicit none >> >> integer :: ierror,rank >> >> call MPI_Init(ierror) >> call MPI_Comm_Rank(MPI_Comm_World,rank,ierror) >> >> ! let master thread wait on [RETURN]-key >> if (rank == 0) then >> read(*,*) >> end if >> >> write(*,*) rank >> >> call mpi_barrier(mpi_comm_world, ierror) end program >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: >> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.open-2Dmpi.org_mailman_listinfo.cgi_users&d=CwICAg&c=IV_clAzoPDE253xZdHuilRgztyh_RiV3wUrLrDQYWSI&r=tqKZ2vRCLufSSXPvzNxBrKr01YPimBPnb-JT-Js0Fmk&m=NPeEHKik35WrcHGDl5ZRq4IC6Le5g03o5YoqD9InrHw&s=eRYTNaknio7tNJFdOMTqvdlNNIq9p6evJoQxuvmqrLs&e= >> Link to this post: >> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.open-2Dmpi.org_community_lists_users_2016_01_28237.php&d=CwICAg&c=IV_clAzoPDE253xZdHuilRgztyh_RiV3wUrLrDQYWSI&r=tqKZ2vRCLufSSXPvzNxBrKr01YPimBPnb-JT-Js0Fmk&m=NPeEHKik35WrcHGDl5ZRq4IC6Le5g03o5YoqD9InrHw&s=2_axdls1JH4Wm5MlkOXRrtXFb2LLVLCleKVx4ybpltU&e= >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: >> http://www.open-mpi.org/community/lists/users/2016/01/28238.php > > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/01/28240.php
