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List:       opensuse-factory
Subject:    [opensuse-factory] Re: [opensuse-science] openMPI mixup in Tumbleweed/Leap 15.x
From:       Todd Rme <toddrme2178 () gmail ! com>
Date:       2018-12-09 15:18:42
Message-ID: CADb7s=tsNnEB63Y94qsJoT-PAv=HYfxsw=BPSc8EhN=Mbd=R6g () mail ! gmail ! com
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On Sat, Dec 8, 2018 at 2:53 PM Stefan Brüns
<stefan.bruens@rwth-aachen.de> wrote:
>
> Hi,
>
> I went through a few packages which have an openMPI dependency or support, and
> found it quite mixed up:
>
> Currently, we have openmpi(1), openmpi2 and openmpi3 in Leap and TW. While
> openmpi3 is currently unused, openmpi1 and openmpi2 are both used, with
> similar frequency:
>
> https://build.opensuse.org/package/binary/openSUSE:Factory/openmpi2:standard/
> standard/x86_64/openmpi2-libs-2.1.5-2.1.x86_64.rpm
> https://build.opensuse.org/package/binary/openSUSE:Factory/openmpi:standard/
> standard/x86_64/openmpi-libs-1.10.7-21.1.x86_64.rpm
>
> Several programs will end up with implicitly linking to both versions, as
> libnetcdf and hdf5 use openmpi1 and boost_mpi uses openmpi2. One example is
> vtk.
>
> As both libraries (libmpi.so.12 and libmpi.so.20) export the same symbols for
> large parts, this is mayhem waiting to happen.
>
> For SLE, different MPI versions/implementations are supported using the HPC
> modules, but for Leap/TW, we should obviously stick with *one* single
> canonical version.
>
> Question now, which version to choose?
>
> Apparently, openmpi2 does not work on all architectures (PPC, PPC64BE) [1],
> and is not supported by some software packages [2].
>
> Are there any drawbacks for using openmpi1 everywhere in TW/Leap 15.x?
>
> I have opened a bug report: https://bugzilla.opensuse.org/show_bug.cgi?
> id=1118861
>
> Kind regards,
>
> Stefan
>
>
> [1] "Stay with openmpi(1) also on PPC", boost, 2018-10-01, https://
> build.opensuse.org/request/show/639401
> [2] "Cntk packages do not support OpenMPI 2+", https://github.com/Microsoft/
> CNTK/issues/3197
>
> --
> Stefan Brüns  /  Bergstraße 21  /  52062 Aachen
> home: +49 241 53809034     mobile: +49 151 50412019

No matter what we pick, I think it would be a good idea to do what we
do with, say, gcc and llvm/clang, where we have separate "openmpi1",
"openmpi2", and "openmpi3" packages, and have the "openmpi" package
refer to the default version.  This would make it easy to change
default versions in the future, or set default versions on a
per-architecture basis.

As for openmpi 1 vs openmpi 2, the problem with openmpi 1 is that it
is unmaintained [1].  The current version of openmpi is actually
version 4.  So using it openmpi 2 as the default comes with all the
problems associated with unmaintained software, especially
network-oriented software.  openmpi 2 also adds support for MPI 3.x
features.

openmpi 2 is supposed to support PPC.  If it doesn't that is probably
a bug that should be reported upstream.  Unfortunately the linked
request doesn't explain what the problem is.


[1] See left sidebar here: https://www.open-mpi.org/software/ompi/v4.0/
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