[mvapich-discuss] FW: Possible bug: Segmentation fault with MPI_Reduce and MPI_IN_PLACE

[Krishna Kandalla]

Hi Alexander,
                  Thank you for reporting this error. Can you please try
running your application by setting the MV2_USE_SHMEM_REDUCE flag to 0. You
can find more information about this run-time variable at :
http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.6rc1.html

<http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.6rc1.html>
Thanks,
Krishna

On Mon, Nov 22, 2010 at 11:06 AM, Alexander Alekhin <
alexander.alekhin at itseez.com> wrote:

> Hi,
>
>
>
> I use MVAPICH2 1.5.1p1 code from svn.
> My mpiname info:
> *MVAPICH2 1.5.1p1 Unofficial Build ch3:mrail*
>
> * *
>
> *Compilation*
>
> *CC: gcc  -g*
>
> *CXX: c++  -g*
>
> *F77: g77  -g*
>
> *F90: f95  -g*
>
>
>
> *Configuration*
>
> *--prefix=$HOME/mvapich2/install --enable-g=all
> --enable-error-messages=all --enable-fast=none*
>
>
>
> My problem is in application failure which uses MPI_IN_PLACE with
> MPI_Reduce operation.
>
>
>
> For example I provide this part of code which generate a segmentation
> fault with 2 processes launched on same node:
>
>
>
> *// myid is rank in MPI_COMM_WORLD (see examples/cpi.c)*
>
> *{*
>
> *    MPI_Group g1, g2;*
>
> *    MPI_Comm comm;*
>
> *    int ranks[2] = { 1, 0 };*
>
> *    MPI_Comm_group(MPI_COMM_WORLD, &g1);*
>
> *    MPI_Group_incl(g1, 2, ranks, &g2);*
>
> * *
>
> *    MPI_Comm_create(MPI_COMM_WORLD, g2, &comm);*
>
> * *
>
> *    if (myid == 0) { // rank 1 of comm (root of Reduce)*
>
> *        int result = myid;*
>
> *        if (MPI_Reduce(MPI_IN_PLACE, &result, 1, MPI_INT, MPI_SUM, 1, comm) != MPI_SUCCESS) // fail is here*
>
> *            exit(1);*
>
> *    } else {*
>
> *        if (MPI_Reduce(&myid, NULL, 1, MPI_INT, MPI_SUM, 1, comm) != MPI_SUCCESS)*
>
> *            exit(1);*
>
> *    }*
>
> * *
>
> *    MPI_Comm_free(&comm);*
>
> *    MPI_Group_free(&g2);*
>
> *    **MPI_Group_free(&g1);*
>
> *}*
>
>
>
> Command to launch:
>
> *mpiexec -np 2 -host <host_name> <binary_file>*
>
>
>
> GDB info:
>
> *0:  Program received signal SIGSEGV, Segmentation fault.*
>
> *0:  0x0000000000411a73 in MPIUI_Memcpy (dst=0x2aaaaadcfc0c,*
>
> *0:      src=0xffffffffffffffff, len=4) at ../../include/mpiimpl.h:122*
>
> *0:  122     memcpy(dst, src, len);*
>
> *0: (gdb) bt*
>
> *0:  #0  0x0000000000411a73 in MPIUI_Memcpy (dst=0x2aaaaadcfc0c,*
>
> *0:      src=0xffffffffffffffff, len=4) at ../../include/mpiimpl.h:122*
>
> *0:  #1  0x0000000000414eb3 in MPIR_Localcopy (sendbuf=0xffffffffffffffff,*
>
> *0:      sendcount=1, sendtype=1275069445, recvbuf=0x2aaaaadcfc0c, recvcount=1,*
>
> *0:      recvtype=1275069445) at helper_fns.c:335*
>
> *0:  #2  0x0000000000410d48 in PMPI_Reduce (sendbuf=0xffffffffffffffff,*
>
> *0:      recvbuf=0x7fffcb044bcc, count=1, datatype=1275069445, op=1476395011,*
>
> *0:      root=1, comm=-1006632960) at reduce_osu.c:1017*
>
>
>
> If I replace MPI_IN_PLACE to variable then all works fine.
>
>
>
> Can somebody check this problem?
>
>
>
> --
>
> Thanks,
>
> Alexander Alekhin
>
>
>
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>
>
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