Re: [OMPI packagers] Possible to have multiple OpenMPIs simultaneously?

2020-11-29 Thread Gilles Gouaillardet
I made a quick check, and the latest 3.1 MPI standard is supported (at 
least) from Open MPI 2.0.*


(you can check the MPI_VERSION and MPI_SUBVERSION macros in 
ompi/include/mpi.h[.in])



please do note that the 2.0 and 2.1 series are no more supported.


Cheers,


Gilles



On 11/30/2020 11:27 AM, Aisha Tammy via ompi-packagers wrote:

On 11/29/20 7:45 PM, Gilles Gouaillardet wrote:

Aisha,

yes, you can install multiple Open MPI implementations in parallel,
simply use a different prefix when running configure.

Newer versions of Open MPI support the latest MPI standard

Makes sense :D

(there is
not a direct link between an Open MPI version
and the MPI standard version though).

Do all OpenMPI major versions support the latest standard?
That would simplify things a lot :D

That being said, with the exception of a few removed/deprecated
subroutines, a given version of the MPI standard is a superset of the
previous versions.
This is at the source level, and Open MPI does not generally guarantee
ABI compatibility between two major versions.
Makes sense too. I was not expecting ABI compatibility between major 
versions.

Last but not least, keep in mind several packages depend on MPI, for
example mpi4py (python bindings), parallel FFTW (Fast Fourier
Transformations), parallel hdf5/netcdf (I/O).
So since Open MPI has generally no ABI compatibility between major
versions, you would also need multiple versions of the dependents
packages (one per Open MPI version).

Yes, I am aware that we would need multiple "slots" for each dependent
packages. We have a half finished project that was started a couple
of years ago which does this slotting of packages and MPI implementations.

Thanks a lot for the answers.

The unfortunate reality is that the default MPI pakages are badly 
managed in almost

all operating systems and any decent cluster has a sysadmin who cooks
up a solution for their use case :(
Even users who want to use OpenMPI, most of the times, install it 
manually to

tune and get a better control over it.

Making the default packages saner at the operating system level should 
hopefully

help a lot of people.

Best,
Aisha


Cheers,

Gilles

On Mon, Nov 30, 2020 at 6:00 AM Aisha Tammy via ompi-packagers
  wrote:

  Hi,
   I am a package manager for Gentoo Linux and we are currently trying
to get better MPI support for our package tree.

A curious question was whether it was possible to have multiple OpenMPI
implementations installed in parallel?
There seem to be multiple OpenMPI versions being supported and presumably
they are supporting different standards of MPI - 2, 3, 3.1 ?

Am I correct in making this assumption?
If so, it should be possible to allow multiple OpenMPI versions together.

Thanks a lot,
Aisha

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Re: [OMPI packagers] Possible to have multiple OpenMPIs simultaneously?

2020-11-29 Thread Gilles Gouaillardet
Aisha,

yes, you can install multiple Open MPI implementations in parallel,
simply use a different prefix when running configure.

Newer versions of Open MPI support the latest MPI standard (there is
not a direct link between an Open MPI version
and the MPI standard version though).
That being said, with the exception of a few removed/deprecated
subroutines, a given version of the MPI standard is a superset of the
previous versions.
This is at the source level, and Open MPI does not generally guarantee
ABI compatibility between two major versions.

Last but not least, keep in mind several packages depend on MPI, for
example mpi4py (python bindings), parallel FFTW (Fast Fourier
Transformations), parallel hdf5/netcdf (I/O).
So since Open MPI has generally no ABI compatibility between major
versions, you would also need multiple versions of the dependents
packages (one per Open MPI version).

Cheers,

Gilles

On Mon, Nov 30, 2020 at 6:00 AM Aisha Tammy via ompi-packagers
 wrote:
>
>  Hi,
>   I am a package manager for Gentoo Linux and we are currently trying
> to get better MPI support for our package tree.
>
> A curious question was whether it was possible to have multiple OpenMPI
> implementations installed in parallel?
> There seem to be multiple OpenMPI versions being supported and presumably
> they are supporting different standards of MPI - 2, 3, 3.1 ?
>
> Am I correct in making this assumption?
> If so, it should be possible to allow multiple OpenMPI versions together.
>
> Thanks a lot,
> Aisha
>
> ___
> ompi-packagers mailing list
> ompi-packagers@lists.open-mpi.org
> https://rfd.newmexicoconsortium.org/mailman/listinfo/ompi-packagers
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