[Mpi-22] MPI-2.2 -- change ABI or not?

[Jeff Squyres]

Dick --

Following a round of discussion here in Chicago, there is general  
consensus on your point.

The have decided to give a little leeway on the C++ bindings, though.   
That is, the C++ ABI may change (e.g., it *has* changed between 2.0  
and 2.1) because most MPI's implement the C++ layer as inline  
functions and therefore don't usually affect the run-time ABI.

For example #59 will definitely change the ABI.  But right now, those  
methods *won't compile* in the C++ bindings (because they are wrong),  
so we can't possibly be breaking any real/user applications.

On Apr 6, 2009, at 7:15 AM, Richard Treumann wrote:

> Changing the ABI strikes me as a disaster. ( I did not notice this  
> discussion until just now )
>
> If anyone is thinking it is OK for the Forum to cause a 2.1  
> application compiled against MPI 2.1 headers to fail on an MPI 2.2  
> version of the same implementation or the reverse (2.1 application  
> compiled with 2.2 headers fails on a 2.1 implementation) then I need  
> to hear a really good reason. And I mean really, awesomely,  
> spectacularly, bodacious ) good.
>
> The user of a parallel application does not always have control over  
> the level of MPI installed on the systems he uses and does not  
> always have the source code to recompile. Some people use multiple  
> systems (same architecture but maybe different MPI version)
>
> It seems like a very bad idea to tell the user of MPI that he must  
> upgrade all MPI software he uses on the same day the system admin  
> installs the MPI 2.2 version of the MPI implementation.
>
> It seems like an equally bad idea to be telling system admins they  
> are forbidden to upgrade to the MPI 2.2 version because one of more  
> critical applications used on the system cannot be easily rebuilt in  
> MPI 2.2 compatible form.
>
> If a shop uses only one ISV application then perhaps they can use  
> the MPI level the ISV specifies but what does a shop that uses  
> assorted ISV applications do if some vendors stick with MPI 2.1  
> headers and others compile for 2.2?
>
> Dick
>
>
> Dick Treumann - MPI Team
> IBM Systems & Technology Group
> Dept X2ZA / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
> Tele (845) 433-7846 Fax (845) 433-8363
>
>
> mpi-22-bounces_at_[hidden] wrote on 04/04/2009 12:20:59 PM:
>
> > [image removed]
> >
> > [Mpi-22] MPI-2.2 -- change ABI or not?
> >
> > Jeff Squyres
> >
> > to:
> >
> > MPI 2.2
> >
> > 04/04/2009 12:25 PM
> >
> > Sent by:
> >
> > mpi-22-bounces_at_[hidden]
> >
> > Please respond to "MPI 2.2"
> >
> > On Apr 4, 2009, at 9:53 AM, Jeff Squyres (jsquyres) wrote:
> >
> > > But the general point may need broad discussion next week --  
> have we
> > > been sure to adhere to the "must be ABI compatible" rule for all
> > > MPI-2.2 issues?
> > >
> > (changed the subjet to be more accurate)
> >
> >
> > I notice that ticket #5 has already had a 1st reading; it will
> > certainly change the ABI.
> >
> > My point: if we are taking a hard line to make it possible for any
> > existing MPI-2.1 application to be able to run against MPI-2.1 and
> > MPI-2.2 versions of the same implementation, we will need to review
> > all MPI-2.2 tickets.
> >
> > --
> > Jeff Squyres
> > Cisco Systems
> >
> > _______________________________________________
> > mpi-22 mailing list
> > mpi-22_at_[hidden]
> > http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
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-- 
Jeff Squyres
Cisco Systems