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Subject: Re: [OMPI users] Upgrade from Open MPI 1.2 to 1.3
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2009-04-27 14:30:36


I think Serge is talking about compiling the application against one
version of Open MPI, linking dynamically, then running against another
version of Open MPI. Since it's dynamically linked, the ORTE/OMPI
interactions are covered (the version of mpirun, libopen-rte, and libmpi
all match). The question of application binary compatibility can
generally be traced to a couple of issues:

   - function signatures of all MPI functions
   - constants in mpi.h changing
   - size of structures due to the bss optimization for globals

I can't remember when we changed function signatures last, but it probably
has happened. They may be minor enough to not matter, and definitely
wouldn't be in the usual set of functions people use (send,recv,wait,
etc.)

The constants in mpi.h have been pretty steady since day 1, although I
haven't checked when they last changed.

The final one actually should be ok for going from later versions of Open
MPI to newer versions, as the structures in question usually grow and
rarely shrink in size.

In other words, it'll probably work, but no one in the group is going to
say anything stronger than that.

Brian

On Mon, 27 Apr 2009, Ralph Castain wrote:

> It's hard for me to believe that would work as there are fundamental
> differences in the MPI-to-RTE interactions between those releases. If it
> does, it could be a fluke - I personally would not trust it.
>
> Ralph
>
> On Mon, Apr 27, 2009 at 12:04 PM, Serge <skhan_at_[hidden]> wrote:
> Hi Jeff,
>
> > That being said, we have fixed this issue and expect to
> support binary
> > compatibility between Open MPI releases starting with
> v1.3.2 (v1.3.1
>
> As far as I can tell from reading the release notes for
> v1.3.2, the binary compatibility has not been announced yet.
> It was rather a bug fix release. Is it correct? Does it mean
> that the compatibility feature is pushed to later releases,
> v1.3.3, 1.3.4?
>
> In my original message (see below) I was looking for advice
> as for a seamless transition from v1.2.x to v1.3.x in a
> shared multi-user environment.
>
> Interestingly enough, recently I noticed that although it's
> impossible to run an application compiled with v1.2.x under
> v1.3.x, the opposite does actually work. An application
> compiled with v1.3.x runs using Open MPI v1.2.x.
> Specifically, I tested an application compiled with v1.3.0
> and v1.3.2, running under Open MPI v1.2.7.
>
> This gives me a perfect opportunity to recompile all the
> parallel applications with v1.3.x, transparently to users;
> and then switch the default Open MPI library from v1.2.7 to
> v1.3.x, when all the apps have been rebuilt.
>
> The problem is that I am not 100% sure in this approach, even
> having some successful tests done.
>
> Is it safe to run an application built with 1.3.x under
> 1.2.x? Does it make sense to you?
>
> = Serge
>
>
> Jeff Squyres wrote:
> Unfortunately, binary compatibility between Open
> MPI release versions has never been guaranteed
> (even between subreleases).
>
> That being said, we have fixed this issue and
> expect to support binary compatibility between
> Open MPI releases starting with v1.3.2 (v1.3.1
> should be released soon; we're aiming for v1.3.2
> towards the beginning of next month).
>
>
>
> On Mar 10, 2009, at 11:59 AM, Serge wrote:
>
> Hello,
>
> We have a number of applications
> built with Open MPI 1.2 in a shared
> multi-user environment. The Open MPI
> library upgrade has been always
> transparent and painless within the
> v1.2 branch. Now we would like to
> switch to Open MPI 1.3 as seamlessly.
> However, an application built with
> ompi v1.2 will not run with the 1.3
> library; the typical error messages
> are given below. Apparently, the type
> ompi_communicator_t has changed.
>
> Symbol `ompi_mpi_comm_null' has
> different size in shared object,
> consider re-linking
> Symbol `ompi_mpi_comm_world' has
> different size in shared object,
> consider re-linking
>
> Do I have to rebuild all the
> applications with Open MPI 1.3?
>
> Is there a better way to do a smooth
> upgrade?
>
> Thank you.
>
> = Serge
>
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