[petsc-users] Ghost communication

[Matthew Knepley]

On Fri, Jun 24, 2011 at 2:38 AM, Milan Mitrovic <milanm at student.ethz.ch>wrote:

> So, any ideas?
>
> when I call MatMult(A,b,x,info) the ghosts get updated. When I call
> KSPSolve(ksp,b,x,info) the ghosts dont get updated (the multiplication
> routine is called... I checked that)... It seems that KSP calles
> MatMult with different vectors... not the original b and x...
>

Yes, that definitely happens. You cannot count on the same vector being
used internally. They are the same type (ghosted), but they may come
from VecDuplicate/Copy(), so anytime you need ghost values, you need
to update.

   Matt
-- 
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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