[Mpi3-ft] FT Working Group Teleconf (today)

[Supalov, Alexander]

Let me think. How will this work if an old (MPI-2) based app is linked against a new (MPI-3) library? The app has already allocated the MPI_Status and that can't be changed without recompilation that is undesirable.

It appears that in this scenario we'll have to have all "old" directly accessible data fields still inside the "new" MPI_Status, with the same sizes and offset/alignment, and then something else, not increasing the MPI_Status size, that can be used for the MPI_Get_count and additional MPI_Get_* functions.

E.g., if the "old" internal "count" field (or whatever serves as such) could be "reused" to keep a pointer for all the MPI_Get_* functions - yes, this might work. Needs extra analysis at the implementation level, though.

-----Original Message-----
From: mpi3-ft-bounces at lists.mpi-forum.org [mailto:mpi3-ft-bounces at lists.mpi-forum.org] On Behalf Of Greg Bronevetsky
Sent: Wednesday, March 24, 2010 5:35 PM
To: MPI 3.0 Fault Tolerance and Dynamic Process Control working Group; MPI 3.0 Fault Tolerance and Dynamic Process Control working Group
Subject: Re: [Mpi3-ft] FT Working Group Teleconf (today)


>I agree with Dick. We're getting very strong ISV feedback that an 
>MPI-3 compatibility break will constitute a serious adoption barrier for them.

The other option would be to have an extra function like 
MPI_Get_count that extracts internal information from MPI_Status 
objects. Can that be implemented without breaking compatibility?

Greg Bronevetsky
Lawrence Livermore National Lab
(925) 424-5756
bronevetsky at llnl.gov
http://greg.bronevetsky.com 

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