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Subject: Re: [OMPI devel] Problem when using struct types at specific offsets
From: Thomas Jahns (jahns_at_[hidden])
Date: 2013-06-21 10:33:27


On 04/08/2013 04:08 PM, Thomas Jahns wrote:
> a colleague of mine has investigated a difficult problem we traced to OpenMPI
> giving incorrectly delivered data on some struct datatypes which use specific
> offsets (on the stack in our case but the problem can be reproduced when using
> specifically chosen slices of an array). Our library is used to aggregate
> several MPI communications in a generic and transparent manner and therefore we
> need to be able to handle any combination of properly aligned offsets and
> component types.
> The attached example program contains the necessary steps to reproduce the problem:
> 1. create the struct types in question
> 2. send/recv the data
> 3. compare to reference (said comparison works on several MPICH2 versions)

our IT service provider has applied the patch to openmpi 1.6.4 and the C
test-case I provided now works but the original code which uses a bigger number
of struct dataypes still fails.

Has anyone already discovered a potential problem with the fix provided in
r28319? I'm asking because developing the C test case is quite some amount of
work and is not easily reproducible with every Fortran compiler because it
depends on the stack layout.

Regards, Thomas

Thomas Jahns
DKRZ GmbH, Department: Application software
Deutsches Klimarechenzentrum
Bundesstraße 45a
D-20146 Hamburg
Phone: +49-40-460094-151
Fax: +49-40-460094-270
Email: Thomas Jahns <jahns_at_[hidden]>