[petsc-users] error in calling VecGetArrayf90()
Ethan Coon
ecoon at lanl.gov
Wed Jan 5 13:03:48 CST 2011
On all processors, the array you get is indexed:
xx_v(1:(Iend-Istart))
while the Istart and Iend are global indices into the global Vec.
It's only by luck that the values on proc 3 are correct (this code
should probably seg fault as it is accessing memory outside of the
bounds of xx_v).
To access the array, you'll want:
do i=1, (Iend-Istart)
write(6,*)'check xx_v',i,xx_v(i),myid
enddo
or (better yet) pass it into a subroutine to get the array indexed
correctly, like demonstrated in the example.
Ethan
On Wed, 2011-01-05 at 11:23 -0600, Peter Wang wrote:
> Thanks, Satish,
>
> The index of the array is modified to i+1:
> !===================
> do i=Istart,Iend-1
> write(6,*)'check xx_v',i+1,xx_v(i+1),myid
> enddo
> !===================
>
> However, only the elements on root process (process 0) and the
> last process (process 3) are corrent, is there any ohter logical
> error?
>
> check xx_v 1 3999.9999999999982 0
> check xx_v 2 3999.9999999999982 0
> check xx_v 3 3999.9999999999982 0
> check xx_v 4 3999.9999999999982 0
> check xx_v 5 3999.9999999999982 0
> check xx_v 6 3000.0000000000005 0
> check xx_v 7 3000.0000000000005 0
> check xx_v 8 2.61360726650019422E-321 1
> check xx_v 9 7.90505033345994471E-323 1
> check xx_v 10 1.69759663277221785E-312 1
> check xx_v 11 6.16840020108069212E-317 1
> check xx_v 12 6.16840316547456717E-317 1
> check xx_v 13 6.16832658529946177E-317 1
> check xx_v 14 1.99665037664579820E-314 2
> check xx_v 15 6.19784009071943448E-317 2
> check xx_v 16 6.20249221284067566E-317 2
> check xx_v 17 6.20218737433719161E-317 2
> check xx_v 18 6.18236051996958238E-317 2
> check xx_v 19 6.16840316547456717E-317 2
> check xx_v 20 6.18107199676522841E-317 3
> check xx_v 21 0.0000000000000000 3
> check xx_v 22 0.0000000000000000 3
> check xx_v 23 0.0000000000000000 3
> check xx_v 24 0.0000000000000000 3
> check xx_v 25 0.0000000000000000 3
>
>
>
> > Date: Tue, 4 Jan 2011 22:49:50 -0600
> > From: balay at mcs.anl.gov
> > To: petsc-users at mcs.anl.gov
> > Subject: Re: [petsc-users] error in calling VecGetArrayf90()
> >
> > 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.
> > > > >
> > > > >
> > > >
> > >
> >
--
-------------------------------------
Ethan Coon
Post-Doctoral Researcher
Mathematical Modeling and Analysis
Los Alamos National Laboratory
505-665-8289
http://www.ldeo.columbia.edu/~ecoon/
-------------------------------------
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