[petsc-users] error in calling VecGetArrayf90()

[Peter Wang]

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.
> > 
> > 
> 
 		 	   		  
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