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Hi Lee,
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<div>Just to be clear re. your original question - the (i,j,k,e) topology is point-based, not cell-based,</div>
<div>so one doesn't have a concept of 6 neighbors unless you are in the interior of a spectral element</div>
<div>or on the face of a spectral element. At an edge or corner, you could have more or fewer than</div>
<div>6 neighbors.</div>
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<div>If you instead define a cell (which would be defined, say, at the centroids of the N^3 cells within each element), you would have 6 neighbors unless you're on the boundary.</div>
<div><br>
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<div>I would normally find these neighbors by invoking calls to setupds and dssum(). In one exchange, you could exchange your neighbors element number. In a subsequent exchange you could exchange the cell index. If you use gs_op() directly, I believe it
supports integer arguments, rather than making the unseeingly an perhaps error-prone conversion to integers, though I've never had any difficulty call dssum directly and using reals.</div>
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<div>It's important to use the gs_op (or equivalent drum) operations as that is the only viable/scalable approach in parallel. (Everything has been tested on anywhere from 1 to 6 million ranks).</div>
<div><br>
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<div>I've done this several times before...and can probably dig up some code to give you cell based data,</div>
<div>assuming that's what you want.</div>
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<div>Best,</div>
<div><br>
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<div>Paul</div>
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<div id="divRpF914689" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov [nek5000-users-bounces@lists.mcs.anl.gov] on behalf of nek5000-users@lists.mcs.anl.gov [nek5000-users@lists.mcs.anl.gov]<br>
<b>Sent:</b> Monday, May 08, 2017 7:38 AM<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> Re: [Nek5000-users] Adjacent vertices / cells<br>
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<p>Hi Paul,</p>
<p><br>
</p>
<p>Thankyou very much for your prompt response,</p>
<p><br>
</p>
<p>I'm tracking an immersed object within the fluid. I can determine whether a velocity point is within the boundary using face normals and dot-products, but I need to know whether it is connected to an outside-boundary cell.</p>
<p><br>
</p>
<p>Cheers,</p>
<p><br>
</p>
<p>Lee</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov <nek5000-users-bounces@lists.mcs.anl.gov> on behalf of nek5000-users@lists.mcs.anl.gov <nek5000-users@lists.mcs.anl.gov><br>
<b>Sent:</b> 08 May 2017 13:26:13<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> Re: [Nek5000-users] Adjacent vertices / cells</font>
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Hi Lee,
<div><br>
</div>
<div>The SEM is more function-based than cell based.</div>
<div><br>
</div>
<div>My guess is that Nek might alread support the higher-level</div>
<div> operation you are trying to implement. What is your</div>
<div>objective?</div>
<div><br>
</div>
<div>Best, Paul</div>
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<div id="divRpF546337" style="direction:ltr"><font face="Tahoma" size="2" color="#000000"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov [nek5000-users-bounces@lists.mcs.anl.gov] on behalf of nek5000-users@lists.mcs.anl.gov [nek5000-users@lists.mcs.anl.gov]<br>
<b>Sent:</b> Monday, May 08, 2017 6:52 AM<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> [Nek5000-users] Adjacent vertices / cells<br>
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<p>Hi all,</p>
<p><br>
</p>
<p>I'm just wondering if there's a way (given a particular velocity cell's local (i,j,k,e) co-ordinates within the domain) to access the 6 adjacent cells - even if they are located inside a different element.</p>
<p><br>
</p>
<p>If so, how does this deal with cells on the boundary, where there may exist fewer than 6 adjacent cells.</p>
<p><br>
</p>
<p>Many thanks,</p>
<p><br>
</p>
<p>Lee </p>
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