[mpich2-dev] [number.cruncher at ntlworld.com: [OMPI users] memcpy overlap in ompi_ddt_copy_content_same_ddt and glibc 2.12]

[Rob Latham]

a glibc optimization is causing problems for openmpi.  is this going
to be a problem for mpich2 ?

==rob

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From: Number Cruncher <number.cruncher at ntlworld.com>
Reply-To: Open MPI Users <users at open-mpi.org>
Subject: [OMPI users] memcpy overlap in ompi_ddt_copy_content_same_ddt and
	glibc 2.12
Date: Wed, 10 Nov 2010 17:11:47 +0000
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To: Open MPI Users <users at open-mpi.org>

Just some observations from a concerned user with a temperamental Open
MPI program (1.4.3):

Fedora 14 (just released) includes glibc-2.12 which has optimized
versions of memcpy, including a copy backward.
http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=6fb8cbcb58a29fff73eb2101b34caa19a7f88eba

I think the overlapping memcpy issue reported previously may be
actively triggered by this optimized memcpy and produce incorrect
data.

Related posts:
http://www.open-mpi.org/community/lists/users/2009/04/9069.php
http://www.open-mpi.org/community/lists/users/2008/01/4918.php
http://www.open-mpi.org/community/lists/users/2007/08/3872.php

Original developer response:
http://www.open-mpi.org/community/lists/users/2007/08/3873.php

Current ticket:
https://svn.open-mpi.org/trac/ompi/ticket/1903

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-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA