I think we should come up with a plan ourselves before discussing with IBM.

Something that involves minimal changes to their code would be best, so that

it is less work for us. Let me digest all the various mails on this topic,

look at what IBM has done, and then come back...

Rajeev 

-----Original Message-----

From: owner-mpich2-core@mcs.anl.gov 

[mailto:owner-mpich2-core@mcs.anl.gov] On Behalf Of Pavan Balaji

Sent: Tuesday, May 06, 2008 4:07 PM

To: mpich2-core@mcs.anl.gov

Subject: Re: [mpich2-core] BG/P patches

So, while we need not use IBM's exact fixes, we should fix 

it in some way --

whatever way we think is right. We can then try to 

propagate those fixes

back to IBM.

Would it make sense to initiate a discussion with IBM about 

this, or is 

it too early?

I personally feel that we should internally use MPI_Offset instead of 

MPI_Aint for datatypes and I/O to calculate the total size 

and leave the 

rest (parts that are broken in the MPI standard) as they 

currently are. 

Specifically, anything that returns an MPI_Aint to the user might 

overflow on 32-bit systems (technically even on 64-bit 

systems, but we 

are some time away for that). But in cases where the user doesn't use 

such functions but MPICH2 internally has to evaluate the 

size, it should 

work fine.

  -- Pavan

-- 

Pavan Balaji

http://www.mcs.anl.gov/~balaji