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Subject: Re: [OMPI users] Segmentation fault in MPI_Init when passing pointers allocated in main()
From: Ralph Castain (rhc_at_[hidden])
Date: 2013-11-12 12:18:38


Kernighan and Richie's C programming language manual - it goes all the way back to the original C definition.

On Nov 12, 2013, at 9:15 AM, Alex A. Granovsky <gran_at_[hidden]> wrote:

> Hello,
>
>> It seems that argv[argc] should always be NULL according to the
>> standard. So OMPI failure is not actually a bug!
>
> could you please point to the exact document where this is explicitly stated?
> Otherwise, I'd assume this is a bug.
>
> Kind regards,
> Alex Granovsky
>
>
> -----Original Message----- From: Matthieu Brucher
> Sent: Tuesday, November 12, 2013 8:56 PM
> To: Open MPI Users
> Subject: Re: [OMPI users] Segmentation fault in MPI_Init when passing pointers allocated in main()
>
> It seems that argv[argc] should always be NULL according to the
> standard. So OMPI failure is not actually a bug!
>
> Cheers,
>
> 2013/11/12 Matthieu Brucher <matthieu.brucher_at_[hidden]>:
>> Interestingly enough, in ompi_mpi_init, opal_argv_join is called
>> without then array length, so I suppose that in the usual argc/argv
>> couple, you have an additional value to argv which may be NULL. So try
>> allocating 3 additional values, the last being NULL, and it may work.
>>
>> Cheers,
>>
>> Matthieu
>>
>> 2013/11/12 Tang, Yu-Hang <yuhang_tang_at_[hidden]>:
>>> I tried the following code without CUDA, the error is still there:
>>>
>>> #include "mpi.h"
>>>
>>> #include <cstdlib>
>>> #include <cstring>
>>> #include <cmath>
>>>
>>> int main(int argc, char **argv)
>>> {
>>> // override command line arguments to make sure cudaengine get the
>>> correct one
>>> char **argv_new = new char*[ argc + 2 ];
>>> for( int i = 0 ; i < argc ; i++ )
>>> {
>>> argv_new[i] = new char[ strlen( argv[i] ) + 1 ];
>>> strcpy( argv_new[i], argv[i] );
>>> }
>>> argv_new[ argc ] = new char[ 32 ];
>>> argv_new[ argc+1 ] = new char[ 32 ];
>>> strcpy( argv_new[argc], "-device" );
>>> sprintf( argv_new[argc+1], "%d", 0 );
>>>
>>> argc += 2;
>>> argv = argv_new;
>>>
>>> MPI_Init(&argc,&argv);
>>>
>>> // do something...
>>>
>>> MPI_Finalize();
>>>
>>> for( int i = 0 ; i < argc ; i++ ) delete [] argv[i];
>>> delete [] argv;
>>> }
>>>
>>> At the end of the program the pointer stored in argv is exactly that of
>>> argv_new so this should not be a problem. Manually inserting printf tells me
>>> that the fault occured at MPI_Init. The code works fine if I use
>>> MPI_Init(NULL,NULL) instead. The same code also compiles and runs without a
>>> problem on my laptop with mpich2-1.4.
>>>
>>> Best,
>>> Yu-Hang
>>>
>>>
>>>
>>> On Tue, Nov 12, 2013 at 11:18 AM, Matthieu Brucher
>>> <matthieu.brucher_at_[hidden]> wrote:
>>>>
>>>> Hi,
>>>>
>>>> Are you sure this is the correct code? This seems strange and not a good
>>>> idea:
>>>>
>>>> MPI_Init(&argc,&argv);
>>>>
>>>> // do something...
>>>>
>>>> for( int i = 0 ; i < argc ; i++ ) delete [] argv[i];
>>>> delete [] argv;
>>>>
>>>> Did you mean argc_new and argv_new instead?
>>>> Do you have the same error without CUDA?
>>>>
>>>> Cheers,
>>>>
>>>> Matthieu
>>>>
>>>>
>>>> 2013/11/12 Tang, Yu-Hang <yuhang_tang_at_[hidden]>:
>>>> > Hi,
>>>> >
>>>> > I tried to augment the command line argument list by allocating my own
>>>> > list
>>>> > of strings and passing them to MPI_Init, yet I got a segmentation > fault
>>>> > for
>>>> > both OpenMPI 1.6.3 and 1.7.2, while the code works fine with MPICH2. > The
>>>> > code is:
>>>> >
>>>> > #include "mpi.h"
>>>> > #include "cuda_runtime.h"
>>>> > #include <cstdlib>
>>>> > #include <cstring>
>>>> > #include <cmath>
>>>> >
>>>> > int main(int argc, char **argv)
>>>> > {
>>>> > int device = 0;
>>>> > int skip = 0;
>>>> > bool skipmode = false;
>>>> > bool specified = false;
>>>> > for( int i = 0 ; i < argc ; i++ )
>>>> > {
>>>> > if ( strcmp( argv[i], "-device" ) == 0 )
>>>> > {
>>>> > i++;
>>>> > if ( argv[i][0] == '-' )
>>>> > {
>>>> > skipmode = true;
>>>> > skip = fabs( atoi( argv[i] ) );
>>>> > }
>>>> > else
>>>> > {
>>>> > skipmode = false;
>>>> > device = atoi( argv[i] );
>>>> > }
>>>> > specified = true;
>>>> > }
>>>> > }
>>>> >
>>>> > if ( !specified || skipmode )
>>>> > {
>>>> > char* var;
>>>> > int dev_count, local_rank = 0;
>>>> > if ( (var = getenv("SLURM_LOCALID")) != NULL) local_rank =
>>>> > atoi(var);
>>>> > else if( (var = getenv("MV2_COMM_WORLD_LOCAL_RANK")) != NULL)
>>>> > local_rank = atoi(var);
>>>> > else if( (var = getenv("OMPI_COMM_WORLD_LOCAL_RANK")) != NULL)
>>>> > local_rank = atoi(var);
>>>> > cudaGetDeviceCount( &dev_count );
>>>> > if ( skipmode )
>>>> > {
>>>> > device = 0;
>>>> > if ( device == skip ) local_rank++;
>>>> > while( local_rank-- > 0 )
>>>> > {
>>>> > device = (++device) % dev_count;
>>>> > if ( device == skip ) local_rank++;
>>>> > }
>>>> > }
>>>> > else device = local_rank % dev_count;
>>>> > }
>>>> >
>>>> > // override command line arguments to make sure cudaengine get the
>>>> > correct one
>>>> > char **argv_new = new char*[ argc + 2 ];
>>>> > for( int i = 0 ; i < argc ; i++ )
>>>> > {
>>>> > argv_new[i] = new char[ strlen( argv[i] ) + 1 ];
>>>> > strcpy( argv_new[i], argv[i] );
>>>> > }
>>>> > argv_new[ argc ] = new char[ 32 ];
>>>> > argv_new[ argc+1 ] = new char[ 32 ];
>>>> > strcpy( argv_new[argc], "-device" );
>>>> > sprintf( argv_new[argc+1], "%d", device );
>>>> > argc += 2;
>>>> > argv = argv_new;
>>>> >
>>>> > cudaSetDevice( device );
>>>> >
>>>> > MPI_Init(&argc,&argv);
>>>> >
>>>> > // do something...
>>>> >
>>>> > MPI_Finalize();
>>>> >
>>>> > cudaDeviceReset();
>>>> > for( int i = 0 ; i < argc ; i++ ) delete [] argv[i];
>>>> > delete [] argv;
>>>> > }
>>>> >
>>>> > When compiled using nvcc -ccbin mpic++, The error I got was:
>>>> >
>>>> > [jueying:16317] *** Process received signal ***
>>>> > [jueying:16317] Signal: Segmentation fault (11)
>>>> > [jueying:16317] Signal code: Address not mapped (1)
>>>> > [jueying:16317] Failing at address: 0x21
>>>> > [jueying:16317] [ 0] /usr/lib64/libpthread.so.0() [0x39e5e0f000]
>>>> > [jueying:16317] [ 1] /usr/lib64/libc.so.6() [0x39e5760551]
>>>> > [jueying:16317] [ 2]
>>>> > /opt/openmpi/1.7.2/lib/libopen-pal.so.5(opal_argv_join+0x39)
>>>> > [0x7f460b993079]
>>>> > [jueying:16317] [ 3]
>>>> > /opt/openmpi/1.7.2/lib/libmpi.so.1(ompi_mpi_init+0x347)
>>>> > [0x7f460c106a57]
>>>> > [jueying:16317] [ 4] > /opt/openmpi/1.7.2/lib/libmpi.so.1(MPI_Init+0x16b)
>>>> > [0x7f460c12523b]
>>>> > [jueying:16317] [ 5] ./lmp_jueying() [0x40c035]
>>>> > [jueying:16317] [ 6] /usr/lib64/libc.so.6(__libc_start_main+0xf5)
>>>> > [0x39e5621a05]
>>>> > [jueying:16317] [ 7] ./lmp_jueying() [0x40dd21]
>>>> > [jueying:16317] *** End of error message ***
>>>> >
>>>> > Thanks for the help.
>>>> >
>>>> > Best regards,
>>>> > Yu-Hang Tang
>>>> >
>>>> > _______________________________________________
>>>> > users mailing list
>>>> > users_at_[hidden]
>>>> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>>
>>>>
>>>>
>>>> --
>>>> Information System Engineer, Ph.D.
>>>> Blog: http://matt.eifelle.com
>>>> LinkedIn: http://www.linkedin.com/in/matthieubrucher
>>>> Music band: http://liliejay.com/
>>>> _______________________________________________
>>>> users mailing list
>>>> users_at_[hidden]
>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>
>>>
>>>
>>>
>>> --
>>> Yu-Hang Tang
>>> Room 105, 37 Manning St
>>> Division of Applied Mathematics, Brown University
>>> Providence, RI 02912
>>>
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>>
>> --
>> Information System Engineer, Ph.D.
>> Blog: http://matt.eifelle.com
>> LinkedIn: http://www.linkedin.com/in/matthieubrucher
>> Music band: http://liliejay.com/
>
>
>
> --
> Information System Engineer, Ph.D.
> Blog: http://matt.eifelle.com
> LinkedIn: http://www.linkedin.com/in/matthieubrucher
> Music band: http://liliejay.com/
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users