[petsc-users] Accessing Vector's ghost values

[Bojan Niceno]

Dear Matthew,


thank you for your response.  When I use VecCreateGhost, I get the 
following:

[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/petsc-as/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] PetscCommDuplicate line 140 src/sys/objects/tagm.c
[0]PETSC ERROR: [0] PetscHeaderCreate_Private line 30 
src/sys/objects/inherit.c
[0]PETSC ERROR: [0] VecCreate line 32 src/vec/vec/interface/veccreate.c
[0]PETSC ERROR: [0] VecCreateGhostWithArray line 567 
src/vec/vec/impls/mpi/pbvec.c
[0]PETSC ERROR: [0] VecCreateGhost line 647 src/vec/vec/impls/mpi/pbvec.c
[0]PETSC ERROR: --------------------- Error Message 
------------------------------------
[0]PETSC ERROR: Signal received!
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.2.0, Patch 6, Wed Jan 11 
09:28:45 CST 2012
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: ./PSI-Flow on a arch-linu named lccfd06 by niceno Thu 
Feb 23 19:02:45 2012
[0]PETSC ERROR: Libraries linked from 
/homecfd/niceno/PETSc-3.2-p6/arch-linux2-c-debug/lib
[0]PETSC ERROR: Configure run at Fri Feb 10 10:24:13 2012
[0]PETSC ERROR: Configure options
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: User provided function() line 0 in unknown directory 
unknown file

I don't understand what could be causing it.  I took very good care to 
match the global numbers of ghost cells when calling VecCreateGhost


     Kind regards,


     Bojan


On 2/23/2012 5:53 PM, Matthew Knepley wrote:
> On Thu, Feb 23, 2012 at 10:46 AM, Bojan Niceno <bojan.niceno at psi.ch 
> <mailto:bojan.niceno at psi.ch>> wrote:
>
>     Hi all,
>
>     I've never used a mailing list before, so I hope this message will
>     reach PETSc users and experts and someone might be willing to help
>     me.  I am also novice in PETSc.
>
>     I have developed an unstructured finite volume solver on top of
>     PETSc libraries.  In sequential, it works like a charm.  For the
>     parallel version, I do domain decomposition externally with Metis,
>     and work out local and global numberings, as well as communication
>     patterns between processor.  (The latter don't seem to be needed
>     for PETSc, though.)  When I run my program in parallel, it also
>     works, but I miss values in vectors' ghost points.
>
>     I create vectors with command: VecCreate(PETSC_COMM_WORLD, &x);
>
>     Is it possible to get the ghost values if a vector is created like
>     this?
>
>
> I do not understand this question. By definition, "ghost values" are 
> those not stored in the global vector.
>
>     I have tried to use VecCreateGhost, but for some reason which is
>     beyond my comprehension, PETSc goes berserk when it reaches the
>     command: VecCreateGhost(PETSC_COMM_WORLD, n, PETSC_DECIDE, nghost,
>     ifrom, &x)
>
>
> I think you can understand that "berserk" tells me absolutely nothing. 
> Error message? Stack trace? Did you try to run an
> example which uses VecGhost?
>
>   Thanks,
>
>      Matt
>
>     Can anyone help me?  Either how to reach ghost values for vector
>     created by VecCreate, or how to use VecCreateGhost properly?
>
>
>       Kind regards,
>
>       Bojan
>
>
>
>
> -- 
> What most experimenters take for granted before they begin their 
> experiments is infinitely more interesting than any results to which 
> their experiments lead.
> -- Norbert Wiener


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