On Sat, Dec 11, 2010 at 12:56 AM, Jed Brown <span dir="ltr"><<a href="mailto:jed@59a2.org">jed@59a2.org</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im"><div class="gmail_quote">On Sat, Dec 11, 2010 at 01:53, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>What are you guys talking about? He is asking ("global index for any given 3-d index") for a map</div><div><br></div><div> (i, j, k) --> ((k*N + j)*M + i)*C + c</div><div><br>
</div><div>I can't imagine what you are searching for? The process which owns a given index does not involve a search.</div></blockquote></div><br></div><div>The "global index" is in the "PETSc ordering". He wants this index for an arbitrary (i,j,k) which are not in the ghosted patch of the current process. You either have to store the full mapping, on search lx,ly,lz to locate the owner, then compute the index relative to that process. I don't think that code exists in PETSc. It wouldn't be too hard to write, but it's not the most beautiful thing to do.</div>
</blockquote></div><br>I am not sure why you would need to access regions outside your local piece. For instance,<div>consider how we treat boundary conditions. This is access to a fixed index, but we check on</div><div>
each process</div><div><br></div><div> if (i == i_bc) { <apply BC> }</div><div><br></div><div>Can't you do the same thing with your extra rows?</div><div><br></div><div> Matt<br clear="all"><br>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>
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