There are two ways of using PMIx

- if you use mpirun, then the MPI app (e.g. the PMIx client) will talk
to mpirun and orted daemons (e.g. the PMIx server)
- if you use SLURM srun, then the MPI app will directly talk to the
PMIx server provided by SLURM. (note you might have to srun
--mpi=pmix_v2 or something)

In the former case, it does not matter whether you use the embedded or
external PMIx.
In the latter case, Open MPI and SLURM have to use compatible PMIx
libraries, and you can either check the cross-version compatibility
or build Open MPI with the same PMIx used by SLURM to be on the safe
side (not a bad idea IMHO).

Regarding the hang, I suggest you try different things
- use mpirun in a SLURM job (e.g. sbatch instead of salloc so mpirun
runs on a compute node rather than on a frontend node)
- try something even simpler such as mpirun hostname (both with sbatch
and salloc)
- explicitly specify the network to be used for the wire-up. you can
for example mpirun --mca oob_tcp_if_include if this is
the network subnet by which all the nodes (e.g. compute nodes and
frontend node if you use salloc) communicate.



On Sat, Jan 19, 2019 at 3:31 AM Matt Thompson <> wrote:
> On Fri, Jan 18, 2019 at 1:13 PM Jeff Squyres (jsquyres) via users 
> <> wrote:
>> On Jan 18, 2019, at 12:43 PM, Matt Thompson <> wrote:
>> >
>> > With some help, I managed to build an Open MPI 4.0.0 with:
>> We can discuss each of these params to let you know what they are.
>> > ./configure --disable-wrapper-rpath --disable-wrapper-runpath
>> Did you have a reason for disabling these?  They're generally good things.  
>> What they do is add linker flags to the wrapper compilers (i.e., mpicc and 
>> friends) that basically put a default path to find libraries at run time 
>> (that can/will in most cases override LD_LIBRARY_PATH -- but you can 
>> override these linked-in-default-paths if you want/need to).
> I've had these in my Open MPI builds for a while now. The reason was one of 
> the libraries I need for the climate model I work on went nuts if both of 
> them weren't there. It was originally the rpath one but then eventually (Open 
> MPI 3?) I had to add the runpath one. But I have been updating the libraries 
> more aggressively recently (due to OS upgrades) so it's possible this is no 
> longer needed.
>> > --with-psm2
>> Ensure that Open MPI can include support for the PSM2 library, and abort 
>> configure if it cannot.
>> > --with-slurm
>> Ensure that Open MPI can include support for SLURM, and abort configure if 
>> it cannot.
>> > --enable-mpi1-compatibility
>> Add support for MPI_Address and other MPI-1 functions that have since been 
>> deleted from the MPI 3.x specification.
>> > --with-ucx
>> Ensure that Open MPI can include support for UCX, and abort configure if it 
>> cannot.
>> > --with-pmix=/usr/nlocal/pmix/2.1
>> Tells Open MPI to use the PMIx that is installed at /usr/nlocal/pmix/2.1 
>> (instead of using the PMIx that is bundled internally to Open MPI's source 
>> code tree/expanded tarball).
>> Unless you have a reason to use the external PMIx, the internal/bundled PMIx 
>> is usually sufficient.
> Ah. I did not know that. I figured if our SLURM was built linked to a 
> specific PMIx v2 that I should build Open MPI with the same PMIx. I'll build 
> an Open MPI 4 without specifying this.
>> > --with-libevent=/usr
>> Same as previous; change "pmix" to "libevent" (i.e., use the external 
>> libevent instead of the bundled libevent).
>> > CC=icc CXX=icpc FC=ifort
>> Specify the exact compilers to use.
>> > The MPI 1 is because I need to build HDF5 eventually and I added psm2 
>> > because it's an Omnipath cluster. The libevent was probably a red herring 
>> > as libevent-devel wasn't installed on the system. It was eventually, and I 
>> > just didn't remove the flag. And I saw no errors in the build!
>> Might as well remove the --with-libevent if you don't need it.
>> > However, I seem to have built an Open MPI that doesn't work:
>> >
>> > (1099)(master) $ mpirun --version
>> > mpirun (Open MPI) 4.0.0
>> >
>> > Report bugs to
>> > (1100)(master) $ mpirun -np 4 ./helloWorld.mpi3.SLES12.OMPI400.exe
>> >
>> > It just sits there...forever. Can the gurus here help me figure out what I 
>> > managed to break? Perhaps I added too much to my configure line? Not 
>> > enough?
>> There could be a few things going on here.
>> Are you running inside a SLURM job?  E.g., in a "salloc" job, or in an 
>> "sbatch" script?
> I have salloc'd 8 nodes of 40 cores each. Intel MPI 18 and 19 work just fine 
> (as you'd hope on an Omnipath cluster), but for some reason Open MPI is 
> twitchy on this cluster. I once managed to get Open MPI 3.0.1 working (a few 
> months ago), and it had some interesting startup scaling I liked (slow at low 
> core count, but getting close to Intel MPI at high core count), though it 
> seemed to not work after about 100 nodes (4000 processes) or so.
> --
> Matt Thompson
>    “The fact is, this is about us identifying what we do best and
>    finding more ways of doing less of it better” -- Director of Better Anna 
> Rampton
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