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Subject: Re: [OMPI users] any deadlocks in this sets of MPI_send and MPI_recv ?
From: Huangwei (hz283_at_[hidden])
Date: 2013-09-14 06:21:40


Hi Jeff,

Thank you very much. About the QRECS, it is an allocatable array, and it is
introduced like:

if(myrank .ne. 0) then
     itag = myrank
     call mpi_send(Q.............., 0, itag, .................)
else
     do i=1, N-1
          allocate (QRECS(A(i)))
          itag = i
         call mpi_recv(QRECS......., i, itag, .................)
          deallocate(QRECS)
     enddo

endif

call mpi_bcast(YVAR............., 0, ..............)
Will this cause any problem using this way to introducing QRECS?

Besides, the reasonable why I did not choose mpi_gatherv is that the QRECS
will put into YVAR in a non-consecutive way. for instance, if I have 4
processors, the first element in YVAR is from rank 0, second from rank 1
......fourth from rank 3, and then fifth from rank 0 again, sixth from rank
1 again....... But I will try your suggestion.

Thanks.

best regards,
Huangwei

On 14 September 2013 09:19, Jeff Squyres (jsquyres) <jsquyres_at_[hidden]>wrote:

> At first glance, your code doesn't look problematic. First thing I'd
> check is ensure that QRECS is large enough to hold the incoming data (i.e.,
> that you aren't overwriting the buffer and causing memory corruption, which
> can cause weird/unexplained faults like this).
>
> Also, you might well be able to accomplish the same communication pattern
> with MPI_GATHER (or MPI_GATHERV, if each rank is sending a different amount
> of information).
>
>
> On Sep 14, 2013, at 12:27 AM, Huangwei <hz283_at_[hidden]>
> wrote:
>
> > The code I would like to post is like this:
> >
> > if(myrank .ne. 0) then
> > itag = myrank
> > call mpi_send(Q.............., 0, itag, .................)
> > else
> > do i=1, N-1
> > itag = i
> > call mpi_recv(QRECS......., i, itag, .................)
> > enddo
> >
> > endif
> >
> > call mpi_bcast(YVAR............., 0, ..............)
> >
> > best regards,
> > Huangwei
> >
> >
> >
> >
> >
> >
> > On 13 September 2013 23:25, Huangwei <hz283_at_[hidden]> wrote:
> > Dear All,
> >
> > I have a question about using MPI_send and MPI_recv.
> >
> > The object is as follows:
> > I would like to send an array Q from rank=1, N-1 to rank=0, and then
> rank 0 receives the Q from all other processors. Q will be put into a new
> array Y in rank 0. (of couse this is not realized by MPI). and then
> MPI_bcast is used (from rank 0) to broadcast the Y to all the processors.
> >
> > Fortran Code is like:
> > if(myrank .eq. 0) then
> > itag = myrank
> > call mpi_send(Q.............., 0, itag, .................)
> > else
> > do i=1, N-1
> > itag = i
> > call mpi_recv(QRECS......., i, itag, .................)
> > enddo
> >
> > endif
> >
> > call mpi_bcast(YVAR............., 0, ..............)
> >
> > Problem I met is:
> > In my simulation, time marching is performed, These mpi_send and recv
> are fine for the first three time steps. However, for the fourth time step,
> the looping is only finished from i=1 to i=13, (totally 48 processors).
> That mean after 14th processors, the mpi_recv did not receive the date from
> them. Thus the code hangs there forever. Does deadlock occur for this
> situation? How can I figure out this problem?
> >
> > Thank you so much if anyone can give me some suggestions.
> >
> > best regards,
> > Huangwei
> >
> >
> >
> >
> >
> > _______________________________________________
> > users mailing list
> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
> For corporate legal information go to:
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