[petsc-users] error in calling VecGetArrayf90()

[Satish Balay]

The global index starts at Istart - but the array index starts at 1 [for fortran array]

Satish

On Tue, 4 Jan 2011, Peter Wang wrote:

> 
> In last question, the pointer xx_v is local data.  However, if write them to the monitor or assign them to another array, the value is incorrect.
>  
> The protion of the code to display them on the monitor is like as following:       
>  call MatGetOwnershipRange(A,Istart,Iend,ierr)
>  call VecGetArrayF90(x,xx_v,ierr)  !  Vector x is matched with Matrix A in the same communicator
>  
>     write(*,*)xx_v,myid    ! write the poiner array together
> 
>          do i=Istart,Iend-1
>               write(6,*)'check xx_v',i,xx_v(i),myid    !write the element of the array one by one with local range (Istart to Iend-1)
>          enddo  
>  
>  
> =========The result is as following:  ( the values of the elements from 7 to 20 are not correct !!)
> 
>       3999.9999999999982        3999.9999999999982        3999.9999999999982        3999.9999999999982        3999.9999999999982        3000.0000000000005        3000.0000000000005                0
>       
>       3000.0000000000009        3000.0000000000009        3000.0000000000009        2000.0000000000011        2000.0000000000011        2000.0000000000000                1
> 
>       2000.0000000000009        2000.0000000000009        1000.0000000000003        1000.0000000000003        1000.0000000000003        999.99999999999989                2
> 
>       1000.0000000000000        0.0000000000000000        0.0000000000000000        0.0000000000000000        0.0000000000000000        0.0000000000000000                3
> 
>  
>  check xx_v           0   0.0000000000000000        0.0000000000000000                0
>  check xx_v           1   3999.9999999999982        3999.9999999999982                0
>  check xx_v           2   3999.9999999999982        3999.9999999999982                0
>  check xx_v           3   3999.9999999999982        3999.9999999999982                0
>  check xx_v           4   3999.9999999999982        3999.9999999999982                0
>  check xx_v           5   3999.9999999999982        3999.9999999999982                0
>  check xx_v           6   3000.0000000000005        3000.0000000000005                0
>  check xx_v           7  1.99665037664579820E-314  1.99665037664579820E-314           1
>  check xx_v           8  2.61360726650019422E-321  2.61360726650019422E-321           1
>  check xx_v           9  7.90505033345994471E-323  7.90505033345994471E-323           1
>  check xx_v          10  1.69759663277221785E-312  1.69759663277221785E-312           1
>  check xx_v          11  6.16846344148335980E-317  6.16846344148335980E-317           1
>  check xx_v          12  6.16846640587723485E-317  6.16846640587723485E-317           1
>  check xx_v          13  6.16838982570212945E-317  6.16838982570212945E-317           2
>  check xx_v          14  1.99665037664579820E-314  1.99665037664579820E-314           2
>  check xx_v          15  6.19790333112210216E-317  6.19790333112210216E-317           2
>  check xx_v          16  6.20255545324334334E-317  6.20255545324334334E-317           2
>  check xx_v          17  6.20225061473985929E-317  6.20225061473985929E-317           2
>  check xx_v          18  6.18242376037225006E-317  6.18242376037225006E-317           2
>  check xx_v          19  6.16846640587723485E-317  6.16846640587723485E-317           3
>  check xx_v          20  6.18113523716789609E-317  6.18113523716789609E-317           3
>  check xx_v          21   0.0000000000000000        0.0000000000000000                3
>  check xx_v          22   0.0000000000000000        0.0000000000000000                3
>  check xx_v          23   0.0000000000000000        0.0000000000000000                3
>  check xx_v          24   0.0000000000000000        0.0000000000000000                3
>  
> ======The vector x is :
> Process [0]
> 4000
> 4000
> 4000
> 4000
> 4000
> 3000
> 3000
> Process [1]
> 3000
> 3000
> 3000
> 2000
> 2000
> 2000
> Process [2]
> 2000
> 2000
> 1000
> 1000
> 1000
> 1000
> Process [3]
> 1000
> 0
> 0
> 0
> 0
> 0
> 
> 
> 
>  
> > Date: Tue, 4 Jan 2011 17:50:11 -0600
> > From: balay at mcs.anl.gov
> > To: petsc-users at mcs.anl.gov
> > Subject: Re: [petsc-users] error in calling VecGetArrayf90()
> > 
> > Did you included "finclude/petscvec.h90" in your code - as the example did?
> > 
> > satish
> > 
> > On Tue, 4 Jan 2011, Peter Wang wrote:
> > 
> > > 
> > > I am trying to obtain the value of each element of a solution Vector by KSPsolve(). 
> > > 
> > > The variables are defined according the example of ex4f90.F in \petsc-3.1-p5\src\snes\examples\tutorials\ as following,
> > > 
> > > PetscScalar, pointer :: xx_v(:)
> > > 
> > > ...
> > > call KSPSolve(ksp,b,x,ierr)
> > > call VecView(x,PETSC_VIEWER_STDOUT_WORLD,ierr)
> > > 
> > > call VecGetArrayF90(x,xx_v,ierr)
> > > call VecRestoreArrayF90(x,xx_v,ierr)
> > > 
> > > ...
> > > 
> > > But, the error keeps coming out when call VecGetArrayF90(x,xx_v,ierr) and call VecRestoreArrayF90(x,xx_v,ierr) are not commented off.
> > > 
> > > 
> > > The error information shows:
> > > Caught signal number 11 SEGV: Segmentation Violation, probably memory access out of range
> > > 
> > > [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] F90Array1dCreate line 52 src/sys/f90-src/f90_cwrap.c
> > > [0]PETSC ERROR: --------------------- Error Message ------------------------------------
> > > 
> > > I checked the code according the example, but cannot see any difference to that. Just don't know why the pointer array xx_v doesn't work here? Thanks.
> > > 
> > > 
> > 
>