[petsc-users] Accessing Vector's ghost values

[Bojan Niceno]

Thanks Ju.  I studied this case carefully, and it seems clear to me.  
When I apply the same techniques in my code, I get error messages I sent 
to my reply to Matthew.


     Cheers,


     Bojan


On 2/23/2012 6:46 PM, Ju LIU wrote:
>
>
> 2012/2/23 Bojan Niceno <bojan.niceno at psi.ch <mailto:bojan.niceno at psi.ch>>
>
>     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 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)
>
>     Can anyone help me?  Either how to reach ghost values for vector
>     created by VecCreate, or how to use VecCreateGhost properly?
>
> http://www.mcs.anl.gov/petsc/petsc-current/src/vec/vec/examples/tutorials/ex9.c.html  
> could be helpful.
>
>
>       Bojan
>
>


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