[slurm-users] [EXTERNAL] OpenMPI and Slurm clarification?

Craig cfreese at super.org
Mon Mar 27 18:46:09 UTC 2023

srun: MPI types are...
srun: none
srun: openmpi
srun: pmix_v3
srun: pmi2
srun: pmix

but I'm not sure that tells me much about how I am supposed to be 
building OpenMPI?

On 3/27/23 14:41, Pritchard Jr., Howard wrote:
> HI Craig,
> If you run
> srun –mpi=list
> what does slurm report?
> That will help in determining what argument you want to supply for the 
> –mpi srun option.
> Howard
> *From: *slurm-users <slurm-users-bounces at lists.schedmd.com> on behalf 
> of Craig <cfreese at super.org>
> *Reply-To: *Slurm User Community List <slurm-users at lists.schedmd.com>
> *Date: *Monday, March 27, 2023 at 12:38 PM
> *To: *"slurm-users at lists.schedmd.com" <slurm-users at lists.schedmd.com>
> *Subject: *[EXTERNAL] [slurm-users] OpenMPI and Slurm clarification?
> Can someone please clarify the "best practices" for building OpenMPI 
> compatible with Slurm?
> https://slurm.schedmd.com/mpi_guide.html#open_mpi 
> <https://urldefense.com/v3/__https:/slurm.schedmd.com/mpi_guide.html*open_mpi__;Iw!!Bt8fGhp8LhKGRg!Cb86a2IwxgqfT5fv1_eEByDpAyhly3ZdN6Wwl7Wod9FRPx9HBpvFVojIRgu5oSpti_3jOXhNyvJqEMGs$> 
> tells me what I _can_ do but I'm unclear as to what I _should_ do.
> I've built OpenMPI 4.1.5 with:   --with-pmix --with-libevent=internal  
> --with-hwloc=internal --with-slurm.  If I run an MPI program on my 
> cluster (slurm 18.08.8) with "srun -N2 foo" it seems to work fine. 
> (slurm.conf has MpiDefault=pmix).
> If I "srun --mpi=openmpi -N2 foo" it chokes with:
>     OPAL_ERROR: Unreachable in file
>     ../../../../../opal/mca/pmix/pmix3/pmix3x_client.c at line 112
>     -------------------------------------------------------------------------------------------------------------------
>     This application appears to have been direct launched using "srun",
>     but OMPI was not build with SLURM's PMI support and therefore cannot
>     execute.  There are several options for building PMI support under
>     SLURM, depending upon the SLURM version you are using:
>     version 16.05 or later: you can use SLURM's PMIx support. THis
>     require that you configure and uild SLURM --with-pmix.
>     .
>     .
>     .
> So I guess the question is, what is the "right" way to build OpenMPI 
> with Slurm.  Is the fact that my non-Slurm pmix works "correct" or am 
> I just getting lucky that the various software I have just happens to 
> be compatible.  If I build OpenMPI am I supposed to use Slurm's 
> pmix/libevent/hwloc or is that optional.  If it's optional when/why 
> might I choose to do so. If I need Slurm's versions is there some way 
> to find which pmix/libevent/hwloc my current Slurm install is using? 
> Note: my sysadmins are not going to be helpful as they think Slurm 18 
> and OpenMPI 4.0.2a is adequate for users' needs :^(.
> I like the idea of _not_ tying my OpenMPI to the installed Slurm just 
> in case our support people ever decide to upgrade system software.
> Thanks.
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