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From: Marcus G. Daniels (mdaniels_at_[hidden])
Date: 2006-11-30 17:10:56

Galen Shipman wrote:
> We have found a potential issue with BPROC that may effect Open MPI.
> Open MPI by default uses PTYs for I/O forwarding, if PTYs aren't
> setup on the compute nodes, Open MPI will revert to using pipes.
> Recently (today) we found a potential issue with PTYs and BPROC. A
> simple reader/writer using PTYs causes the writer to hang in
> uninterruptible sleep. The consistency of the process table from the
> head node and the back end nodes is also effected, that is "bps"
> shows no writer process, while "bpsh NODE ps aux" shows the writer
> process in uninterruptible sleep.
> Since Open MPI uses PTYs by default on BPROC this results in ORTED or
> MPI processes being orphaned on compute nodes. The workaround for
> this issue is to configure Open MPI with --disable-pty-support and
> rebuild.
The mpirun manual says that standard input is redirected from /dev/null,
and that standard output of remote nodes will be attached to the node
that invoked mpirun. If this is all caused by some buglet with BPROC
I/O forwarding, perhaps it would help of the slave nodes were invoked
with the equivalent of "bpsh -N"? I wonder if some people see the
problem and others don't depending on stdout (or its absence) from
different applications?