[petsc-users] Accessing Vector's ghost values

Bojan Niceno bojan.niceno at psi.ch
Thu Feb 23 10:46:16 CST 2012

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?

    Kind regards,


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