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
or
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
--
Jonathan Dursi <ljdu...@scinet.utoronto.ca>
