[petsc-users] global index distributed arrays

[Jed Brown]

On Sat, Dec 11, 2010 at 02:14, Mohamad M. Nasr-Azadani <mmnasr at gmail.com>wrote:

> Those nodes, do not follow Poisson equation anymore and they just obey some
> interpolation equations which might need nodes in the BOX stencil of
> width=3.


What kind of boundary condition is this?

In any case, you can create an independent DA of the same size as your
original, but with a box stencil of width 3.  Then
DAGetISLocalToGlobalMapping (generalized to DMGetLocalToGlobalMapping in
petsc-dev) will give you access to those global indices.  You will likely
have to adjust preallocation for these extra entries (unless, somehow
strangely, interpolation actually uses no more points, just from different
places).
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