Hi, Thanks. Let me add that there's quite vocal opposition to changing C++ ABI either. Best regards. Alexander -----Original Message----- From: mpi-22-bounces_at_[hidden] [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Jeff Squyres Sent: Tuesday, April 07, 2009 1:19 PM To: MPI 2.2 Subject: Re: [Mpi-22] MPI-2.2 -- change ABI or not? 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

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