<div class="gmail_quote">On Sat, Dec 11, 2010 at 02:14, Mohamad M. Nasr-Azadani <span dir="ltr"><<a href="mailto:mmnasr@gmail.com">mmnasr@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
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. </blockquote></div><br><div>What kind of boundary condition is this?</div>
<div><br></div><div>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).</div>