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Subject: [OMPI users] any deadlocks in this sets of MPI_send and MPI_recv ?
From: Huangwei (hz283_at_[hidden])
Date: 2013-09-13 18:25:46


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