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Subject: Re: [OMPI users] Spawn and OpenFabrics
From: Allen Barnett (allen_at_[hidden])
Date: 2009-06-02 15:26:36


On Tue, 2009-06-02 at 12:27 -0400, Jeff Squyres wrote:
> On Jun 2, 2009, at 11:37 AM, Allen Barnett wrote:
>
> > std::stringstream ss;
> > ss << "partitioner_program " << COMM_WORLD_SIZE;
> > system( ss.str().c_str() );
> >
>
> You'd probably see the same problem even if you strdup'ed the c_str()
> and system()'ed that.
>
> What kernel are you using?

I've seen it myself on my generic opteron RHEL 4 cluster with kernel
2.6.9-78.0.22; I can't really figure out which version of OFED it uses
(maybe 1.2?). A customer has reported it on an Altix system with SLES
10.2 and kernel 2.6.16.60 with a version of OFED 1.3.

> Does OMPI say that it has IBV fork support?
> ompi_info --param btl openib --parsable | grep have_fork_support

My RHEL4 system reports:

MCA btl: parameter "btl_openib_want_fork_support" (current value: "-1")
MCA btl: information "btl_openib_have_fork_support" (value: "1")

as does the build installed on the Altix system.

> Be sure to also see http://www.open-mpi.org/faq/?category=openfabrics#ofa-fork

We're using OMPI 1.2.8.

> > Also, would MPI_COMM_SPAWN suffer from the same difficulties?
> >
>
>
> It shouldn't; we proxy the launch of new commands off to mpirun /
> OMPI's run-time system. Specifically: the new process(es) are not
> POSIX children of the process(es) that called MPI_COMM_SPAWN.

Is a program started with MPI_COMM_SPAWN required to call MPI_INIT? I
guess what I'm asking is if I will have to make my partitioner an
OpenMPI program as well?

Thanks,
Allen

-- 
Allen Barnett
E-Mail: allen_at_[hidden]
Skype:  allenbarnett