[OMPI users] Segmentation fault in MPI_Init when passing pointers allocated in main()
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
#include
#include
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
Re: [OMPI users] Segmentation fault in MPI_Init when passing pointers allocated in main()
I tried the following code without CUDA, the error is still there:
#include "mpi.h"
#include
#include
#include
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.bruc...@gmail.com> 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 :
> > 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
> > #include
> > #include
> >
> > 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];
>
Re: [OMPI users] Segmentation fault in MPI_Init when passing pointers allocated in main()
After appending an additional NULL the code works now. I admit such use of
argv/argc could be confusing... thanks for pointing that out. And thank you
all for figuring out my problem!
Best,
Yu-Hang
On Tue, Nov 12, 2013 at 12:18 PM, Ralph Castain wrote:
> 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
> 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 :
> >> 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 :
> >>> I tried the following code without CUDA, the error is still there:
> >>>
> >>> #include "mpi.h"
> >>>
> >>> #include
> >>> #include
> >>> #include
> >>>
> >>> 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
> >>> 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 :
> >>>> > Hi,
> >>>> >
> >>>> > I tried to augment the command line argument list by allocating my
> own
> >>>> > list
> >>>> > of strings and passing them to MPI_In
