On 8/16/07, George Bosilca <bosi...@eecs.utk.edu> wrote: > Well, finally someone discovered it :) I know about this problem for > quite a while now, it pop up during our own valgrind test of the > collective module in Open MPI. However, it never create any problems > in the applications, at least not as far as I know. That's why I'm > reticent to replace the memcpy by a memmove (where the arguments are > allowed to overlap) as there is a performance penalty.
George, I believe I also reported this some time ago, and your comments were the same :-). No time to dive into the internals, but for my the question is: What's going on in Comm::Split() that it falls to copy everlapping memory? It is expected, or it is perhaps a bug? Regards, > > george. > > On Aug 16, 2007, at 9:31 AM, Allen Barnett wrote: > > > Hi: > > I was running my OpenMPI 1.2.3 application under Valgrind and I > > observed > > this error message: > > > > ==14322== Source and destination overlap in memcpy(0x41F5BD0, > > 0x41F5BD8, > > 16) > > ==14322== at 0x49070AD: memcpy (mc_replace_strmem.c:116) > > ==14322== by 0x4A45CF4: ompi_ddt_copy_content_same_ddt > > (in /home/scratch/DMP/RHEL4-GCC4/lib/libmpi.so.0.0.0) > > ==14322== by 0x7A6C386: ompi_coll_tuned_allgather_intra_bruck > > (in /home/scratch/DMP/RHEL4-GCC4/lib/openmpi/mca_coll_tuned.so) > > ==14322== by 0x4A29FFE: ompi_comm_split > > (in /home/scratch/DMP/RHEL4-GCC4/lib/libmpi.so.0.0.0) > > ==14322== by 0x4A4E322: MPI_Comm_split > > (in /home/scratch/DMP/RHEL4-GCC4/lib/libmpi.so.0.0.0) > > ==14322== by 0x400A26: main > > (in /home/scratch/DMP/severian_tests/ompi/a.out) > > > > Attached is a reduced code example. I run it like: > > > > mpirun -np 3 valgrind ./a.out > > > > I only see this error if there are an odd number of processes! I don't > > know if this is really a problem or not, though. My OMPI application > > seems to work OK. However, the linux man page for memcpy says > > overlapping range copying is undefined. > > > > Other details: x86_64 (one box, two dual-core opterons), RHEL 4.5, > > OpenMPI-1.2.3 compiled with the RHEL-supplied GCC 4 (gcc4 (GCC) 4.1.1 > > 20070105 (Red Hat 4.1.1-53)), valgrind 3.2.3. > > > > Thanks, > > Allen > > > > > > -- > > Allen Barnett > > Transpire, Inc. > > e-mail: al...@transpireinc.com > > Ph: 518-887-2930 > > > > <main.c><info.bz2>_______________________________________________ > > users mailing list > > us...@open-mpi.org > > http://www.open-mpi.org/mailman/listinfo.cgi/users > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- Lisandro Dalcín --------------- Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC) Instituto de Desarrollo Tecnológico para la Industria Química (INTEC) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) PTLC - Güemes 3450, (3000) Santa Fe, Argentina Tel/Fax: +54-(0)342-451.1594
