[petsc-users] Error in VecAssemeblyBegin after VecView

[Johannes.Huber at unibas.ch]

Hi all,
thanks a lot for you help.
I tracked the problem down to a minimal program and found, that it  
looks like I'm doing something wrong when using the matlab format.  
Here is the minimal program:
#include <petscvec.h>
static char help[] = "Matlab output.\n\n";
int main (int argc, char** argv)
{
   PetscInitialize(&argc,&argv,(char*)0,help);
   Vec b;
   PetscInt ierr;
   int r;
   MPI_Comm_rank(PETSC_COMM_WORLD,&r);
   ierr=VecCreate(PETSC_COMM_WORLD,&b); CHKERRQ(ierr);
   ierr=VecSetSizes(b,10,PETSC_DECIDE); CHKERRQ(ierr);
   ierr=VecSetFromOptions(b); CHKERRQ(ierr);
   ierr=VecZeroEntries(b); CHKERRQ(ierr);
   ierr=VecAssemblyBegin(b); CHKERRQ(ierr);
   ierr=VecAssemblyEnd(b); CHKERRQ(ierr);

   PetscViewer File;
   ierr=PetscViewerASCIIOpen(PETSC_COMM_WORLD,"Test.m",&File); CHKERRQ(ierr);
   ierr=PetscViewerSetFormat(File,PETSC_VIEWER_ASCII_MATLAB);  
CHKERRQ(ierr);  // crash
   //ierr=PetscViewerSetFormat(File,PETSC_VIEWER_ASCII_INDEX);  
CHKERRQ(ierr);  //works
   //ierr=PetscViewerSetFormat(File,PETSC_VIEWER_ASCII_DENSE);  
CHKERRQ(ierr);  //works
   ierr=VecView(b,File); CHKERRQ(ierr);
   ierr=PetscViewerDestroy(&File); CHKERRQ(ierr);

   printf("[%d]: %d\n",r,__LINE__);
   VecAssemblyBegin(b);
   printf("[%d]: %d\n",r,__LINE__);
   VecAssemblyEnd(b);
   ierr=VecDestroy(&b); CHKERRQ(ierr);
   MPI_Barrier(PETSC_COMM_WORLD);
   PetscFinalize();
   return 0;
}
Does anybody know, what's wrong with this?

Thanks a lot,
     Hannes

Quoting Barry Smith <bsmith at mcs.anl.gov>:

>
> On Jan 3, 2012, at 6:59 AM, Jed Brown wrote:
>
>> On Tue, Jan 3, 2012 at 06:41, <Johannes.Huber at unibas.ch> wrote:
>> The first assembly works well, and I would agree, if the first  
>> assmebly crashed. However, it's the second assembly call and in  
>> between those two calls, all I'm doing is viewing the vector.
>>
>> Use a debugger to set a breakpoint in VecSetValues(); maybe  
>> starting after your first assemble. Also try Valgrind, it could be  
>> memory corruption.
>
> http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
>
>
>>
>> You can also break in the first VecAssemblyBegin and do
>>
>> (gdb) p &vec->stash.insertmode
>> $1 = (InsertMode *) 0xADDRESS
>> (gdb) wat *$1
>> Hardware watchpoint 3: *$1
>> (gdb) c
>> ... breaks when insertmode is modified for any reason.
>
>



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