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Subject: Re: [OMPI users] EXTERNAL: Re: MPI_GET beyond 2 GB displacement
From: Price, Brian M (N-KCI) (brian.m.price_at_[hidden])
Date: 2010-07-07 17:51:41


Jeff,

I understand what you've said about 32-bit signed INTs, but in my program, the displacement variable that I use for the MPI_GET call is a 64-bit INT (KIND = 8).

In fact, the only thing in my program that isn't a 64-bit INT is the array that I'm trying to transfer values from.

I would post my entire test program, but I don't have direct internet access from the machine that I'm working on. Do you need to see the test program?

Am I still missing something?

Thanks.

-----Original Message-----
From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On Behalf Of Jeff Squyres
Sent: Wednesday, July 07, 2010 10:39 AM
To: Open MPI Users
Subject: EXTERNAL: Re: [OMPI users] MPI_GET beyond 2 GB displacement

Sorry for the delay in replying. :-(

It's because for a 32 bit signed int, at 2GB, the value turns negative.

On Jun 29, 2010, at 1:46 PM, Price, Brian M (N-KCI) wrote:

> OpenMPI version: 1.3.3
>
> Platform: IBM P5
>
> Built OpenMPI 64-bit (i.e., CFLAGS=-q64, CXXFLAGS=-q64, -FFLAGS=-q64,
> -FCFLAGS=-q64)
>
> FORTRAN 90 test program:
> - Create a large array (3.6 GB of 32-bit INTs)
> - Initialize MPI
> - Create a large window to encompass large array (3.6 GB)
> - Have PE 0 get 1 32-bit INT from PE1
> o Lock the window
> o MPI_GET
> o Unlock the window
> - Free the window
> - Finalize MPI
>
> Built FORTRAN 90 test program 64-bit using OpenMPI wrapper compiler (mpif90 -q64).
>
> Why would this MPI_GET work fine with displacements all the way up to just under 2 GB, and then fail as soon as the displacement hits 2 GB?
>
> The MPI_GET succeeds with a displacement of 2147483644 (4 bytes less than 2 GB).
>
> I get a segmentation fault (address not mapped) when the displacement is 2147483648 (2 GB) or larger.
>
> Thanks.
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users

--
Jeff Squyres
jsquyres_at_[hidden]
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