[petsc-users] MatPtAP problem after subsequent call to MatDuplicate

[Hong]

Samuel:
You try to do following:
1) Create A;
2) Create P;
3) C = PtAP:
     CALL MatPtAP(matA,matP,MAT_INITIAL_MATRIX,PETSC_DEFAULT_REAL,
matC,ierr);
4) MatDestroy(matA,ierr);
5) MatDuplicate(matC,MAT_COPY_VALUES,matA,ierr);
6) MatView(matA,PETSC_VIEWER_STDOUT_WORLD,ierr);

The error occurs at (6). Do you get any error for
MatView(matC)?

C has some special data structures as a matrix product which could be lost
during
MatDuplicate for matA. It might be a bug in our code. I'll check it.

Hong


> Hi there,
>
> I am getting error messages after using MatPtAP to create a new matrix C =
> Pt*A*P and then trying to assign A=C. The following is a minimal example
> reproducing the problem:
>
> #include "slepc/finclude/slepc.h"
>       USE slepcsys
>       USE slepceps
>       IMPLICIT NONE
>       LOGICAL :: cause_error
>       ! --- pure PETSc
>       PetscErrorCode :: ierr
>       PetscScalar :: vals(3,3), val
>       Mat :: matA, matP, matC
>       PetscInt :: m,idxn(3),idxm(3),idone(1)
>
>       ! initialize SLEPc & Petsc etc.
>       CALL SlepcInitialize(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);
>
>       ! [.... call to MatSetValues to set values of matA]
>
>       ! assemble matrix
>       CALL MatAssemblyBegin(matA,MAT_FINAL_ASSEMBLY,ierr); CHKERRQ(ierr);
>       CALL MatAssemblyEnd(matA,MAT_FINAL_ASSEMBLY,ierr); CHKERRQ(ierr);
>
>       ! duplicate matrix
>       CALL MatDuplicate(matA,MAT_DO_NOT_COPY_VALUES,matP,ierr);
> CHKERRQ(ierr);
>
>      ! [.... call to MatSetValues to set values of matP]
>
>       ! assemble matrix
>       CALL MatAssemblyBegin(matP,MAT_FINAL_ASSEMBLY,ierr); CHKERRQ(ierr);
>       CALL MatAssemblyEnd(matP,MAT_FINAL_ASSEMBLY,ierr); CHKERRQ(ierr);
>
>       ! compute C=Pt*A*P
>       cause_error = .TRUE. ! set to .TRUE. to cause error, .FALSE. seems
> to work fine
>       IF(.NOT.cause_error) THEN
>          CALL MatDuplicate(matA,MAT_COPY_VALUES,matC,ierr); CHKERRQ(ierr);
>       ELSE
>          CALL MatPtAP(matA,matP,MAT_INITIAL_MATRIX,PETSC_DEFAULT_REAL,matC,ierr);
> CHKERRQ(ierr);
>       END IF
>
>       ! destroy matA and duplicate A=C
>       CALL MatDestroy(matA,ierr); CHKERRQ(ierr);
>       CALL MatDuplicate(matC,MAT_COPY_VALUES,matA,ierr); CHKERRQ(ierr);
>
>       ! display resulting matrix A
>       CALL MatView(matA,PETSC_VIEWER_STDOUT_WORLD,ierr); CHKERRQ(ierr);
>
> Whether A and P are assigned any values doesn't seem to matter at all. The
> error message I'm getting is:
>
> Mat Object: 1 MPI processes
>   type: mpiaij
> [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: [0] MatView_MPIAIJ_PtAP line 23
> /home/lanthale/Progs/petsc-3.8.2/src/mat/impls/aij/mpi/mpiptap.c
> [0]PETSC ERROR: [0] MatView line 949 /home/lanthale/Progs/petsc-3.
> 8.2/src/mat/interface/matrix.c
> [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
>
> Could someone maybe tell me where I'm doing things wrong? The documentation
> for MatPtAP
> <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatPtAP.html>
> says that C will be created and that this routine is "currently only
> implemented for pairs of AIJ matrices and classes which inherit from AIJ".
> Does this maybe exclude MPIAIJ matrices?
>
> Thanks,
> Samuel
>
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