I think it's both; Any compiled application that is running against any specific implementation does not have to recompile/rebuild to continue and run against an updated implementation that is compliant with MPI 2.2. i.e., MPI 2.2 does not mandate any runtime incompatibility. An example for such incompatibility would be to for a change of the rank parameter from int to MPI_Aint. Plus - any application that recompiles with the new MPI 2.2 headers should not incur any (new) compiler errors. The first rule is significant to ISV's that release binary implementation. Without this requirement, MPI 2.2 would create a significant backward compatibility to those implementing. Thanks, .Erez -----Original Message----- From: mpi-22-bounces_at_[hidden] [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Jeff Squyres Sent: Friday, April 03, 2009 11:07 AM To: MPI Forum Subject: Re: [Mpi-22] [MPI Forum] #59: Clarification on MPI::FILE_NULL, MPI::WIN_NULL and MPI::COMM_NULL This is worth raising to the list. What is the rule for 2.2 -- that existing MPI applications must be able to run with no changes against an MPI-2.2 library? Or is it that existing MPI applications must be able to compile and run with no source code changes against an MPI-2.2 implementation? I hope it's the latter; this change is relatively important. On Apr 3, 2009, at 5:56 AM, MPI Forum wrote:

#59: Clarification on MPI::FILE_NULL, MPI::WIN_NULL and MPI::COMM_NULL ----------------------------------- +---------------------------------------- Reporter: hubertritzdorf | Owner: hubertritzdorf Type: Correction to standard | Status: new Priority: Waiting for reviews | Milestone: 2009/04/06 Chicago Version: MPI 2.2 | Resolution: Keywords: | Implementation: Completed ----------------------------------- +---------------------------------------- Changes (by asupalov):

* cc: alexander.supalov_at_[hidden] (added)

Comment:

Aren't we changing C++ ABI herewith? If so, we may want to postpone this change till MPI-3.

-- Ticket URL: <https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/59#comment:33

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