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Subject: Re: [OMPI users] Random hangs using btl sm with OpenMPI 1.3.2/1.3.3 + gcc4.4?
From: Jonathan Dursi (ljdursi_at_[hidden])
Date: 2009-09-21 17:09:35

Continuing the conversation with myself:

Google pointed me to Trac ticket #1944, which spoke of deadlocks in
looped collective operations; there is no collective operation anywhere
in this sample code, but trying one of the suggested workarounds/clues:
  that is, setting btl_sm_num_fifos to at least (np-1) seems to make
things work quite reliably, for both OpenMPI 1.3.2 and 1.3.3; that is,
while this

mpirun -np 6 -mca btl sm,self ./diffusion-mpi

invariably hangs (at random-seeming numbers of iterations) with OpenMPI
1.3.2 and sometimes hangs (maybe 10% of the time, again seemingly
randomly) with 1.3.3,

mpirun -np 6 -mca btl tcp,self ./diffusion-mpi


mpirun -np 6 -mca btl_sm_num_fifos 5 -mca btl sm,self ./diffusion-mpi

always succeeds, with (as one might guess) the second being much faster...


Jonathan Dursi     <ljdursi_at_[hidden]>