[petsc-users] MatZeroRowsColumns

[Jed Brown]

Samuel Lanthaler <s.lanthaler at gmail.com> writes:

> Ah, great. I didn't understand that "optional" arguments are not 
> optional in the fortran sense of the word. After setting up two vectors 
> to pass to the routine, the program works. Thank you very much!
>
> One additional question: In the documentation, it is written that I can 
> pass PETSC_NULL for these two vectors, if I don't actually need them. 
> That probably only works in C, but not in fortran. Is there a 
> corresponding argument I can pass to the routine in fortran? It seems, 
> that PETSC_NULL_REAL doesn't work; is there some other PETSC_NULL_XXX 
> that should be passed in this case from fortran? 

PETSC_NULL_OBJECT

> If not, then I'll just stick to creating vectors and distroying them
> afterwards, which is fine for me as well.
>
> Cheers,
> Sam
>
>
> On 11/24/2017 01:56 AM, Smith, Barry F. wrote:
>> MatZeroRowsColumns() as two vector arguments you are missing
>>
>>
>>> On Nov 23, 2017, at 2:43 PM, Samuel Lanthaler <s.lanthaler at gmail.com> wrote:
>>>
>>> Hi there,
>>> I'm new to PETSc and have been trying to do some basic manipulation of matrices in fortran, but don't seem to be able to set a row/column to zero using the MatZeroRowsColumns command: The following is a small example program:
>>>
>>> ! initialize PETSc
>>>    CALL PetscInitialize(PETSC_NULL_CHARACTER,ierr)
>>>
>>>    ! Set up a new matrix
>>>    m = 3
>>>    CALL MatCreate(PETSC_COMM_WORLD,matA,ierr); CHKERRQ(ierr);
>>>    CALL MatSetType(matA,MATMPIAIJ,ierr); CHKERRQ(ierr);
>>>    CALL MatSetSizes(matA,PETSC_DECIDE,PETSC_DECIDE,m,m,ierr); CHKERRQ(ierr);
>>>    CALL MatMPIAIJSetPreallocation(matA,3,PETSC_NULL_INTEGER,3,PETSC_NULL_INTEGER,ierr); CHKERRQ(ierr);
>>>
>>>    ! set values of matrix
>>>    vals(1,:) = (/1.,2.,3./)
>>>    vals(2,:) = (/4.,5.,6./)
>>>    vals(3,:) = (/7.,8.,9./)
>>>    !
>>>    idxm = (/0,1,2/)
>>>    idxn = (/0,1,2/)
>>>    !
>>>    CALL MatSetValues(matA,3,idxm,3,idxn,vals,INSERT_VALUES,ierr); CHKERRQ(ierr);
>>>    
>>>    ! assemble matrix
>>>    CALL MatAssemblyBegin(matA,MAT_FINAL_ASSEMBLY,ierr); CHKERRQ(ierr);
>>>    CALL MatAssemblyEnd(matA,MAT_FINAL_ASSEMBLY,ierr); CHKERRQ(ierr);
>>>   
>>>    ! set one row/column to zero, put 6.0d0 on diagonal
>>>    idone(1) = 2
>>>    val = 6.0d0
>>>    CALL MatZeroRowsColumns(matA,1,idone,val,ierr); CHKERRQ(ierr);
>>>
>>> ! finalize PETSc
>>>    CALL PetscFinalize(PETSC_NULL_CHARACTER,ierr)
>>>
>>> When running the program, I get the following error message:
>>>
>>> [0]PETSC ERROR: ------------------------------------------------------------------------
>>> [0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, probably memory access out of range
>>> [0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
>>> [0]PETSC ERROR: or see http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
>>> [0]PETSC ERROR: or try http://valgrind.org on GNU/linux and Apple Mac OS X to find memory corruption errors
>>> [0]PETSC ERROR: likely location of problem given in stack below
>>> [0]PETSC ERROR: ---------------------  Stack Frames ------------------------------------
>>> [0]PETSC ERROR: Note: The EXACT line numbers in the stack are not available,
>>> [0]PETSC ERROR:       INSTEAD the line number of the start of the function
>>> [0]PETSC ERROR:       is given.
>>> [0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
>>> [0]PETSC ERROR: Signal received
>>> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
>>> [0]PETSC ERROR: Petsc Release Version 3.8.2, Nov, 09, 2017
>>> [0]PETSC ERROR: ./test on a arch-complex-debug named sam-ThinkPad-T450s by sam Thu Nov 23 23:28:15 2017
>>> [0]PETSC ERROR: Configure options PETSC_DIR=/home/sam/Progs/petsc-3.8.2 PETSC_ARCH=arch-complex-debug --with-scalar-type=complex
>>> [0]PETSC ERROR: #1 User provided function() line 0 in  unknown file
>>> --------------------------------------------------------------------------
>>> MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
>>> with errorcode 59.
>>> Would someone be so kind as to tell me what I'm doing wrong? Thank you!
>>>
>>> Best regards,
>>> Sam