<div dir="ltr"><div class="gmail_quote"><div dir="ltr">On Fri, Aug 31, 2018 at 4:11 PM Smith, Barry F. <<a href="mailto:bsmith@mcs.anl.gov">bsmith@mcs.anl.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">> On Aug 31, 2018, at 2:52 PM, Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>> wrote:<br>
> <br>
> On Fri, Aug 31, 2018 at 2:20 PM Smith, Barry F. <<a href="mailto:bsmith@mcs.anl.gov" target="_blank">bsmith@mcs.anl.gov</a>> wrote:<br>
> <br>
> PETSc developers,<br>
> <br>
> There are a variety of "interpolation" modules in PETSc but the documentation is scattered (mostly missing). Could everyone who knows anything about the various modules provide a little information about which modes exist as interfaces and which have actual supporting code and expected usage? Anything duplicative?<br>
> <br>
> 1) nested DM to DM (mesh to mesh) of the same type of DM seems to be supported for DMDA and DMPLEX using DMCreateInterpolation(). But what is DMPlexComputeInterpolatorNested(DM, DM, Mat, void *), how is it different? (Note usr context is not used)<br>
> <br>
> DMCreateInterpolation() says nothing about nesting, and in fact lets people create arbitrary algebraic interpolation. For DMPlex, we support<br>
> both nested and non-nested MG (Patrick says there is a subtle bug in non-nested), but my tests pass for this. The Nested case is obviously much easier and has a fixed element matrix, whereas non-nested uses point location.<br>
> <br>
> 2) non-nested DM to DM. DMPlexComputeInterpolatorGeneral(DM, DM, Mat, void *); (and what does "local portion" mean?) (also the usr context? is not used).<br>
> <br>
> We can take out "local portion". That was me talking to myself.<br>
<br>
Why do DMPlexComputeInterpolatorNested() and DMPlexComputeInterpolatorGeneral() exist if DMCreateInterpolation() handles both nested and non-nested? Does DMCreateInterpolation() use them? If so they should be made private and there name changed: for example <br>
<br>
DMCreateInterpolation_Plex_Nested() and DMCreateInterpolation_Plex_General(). Having multiple interfaces with different names that do the same thing is very confusing and not the way we do things in PETSc.<br></blockquote><div><br></div><div>Yes, they are called by DMCreateInterpolation() and name changes are appropriate.</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
> <br>
> 3) DM to a set of points (mesh to points) with DMInterpolationInfo and the routines DMInterpolationEvaluate() etc. Is this fully implemented for DMPLEX, DMDA?<br>
> <br>
> This relies on the DMLocatePoints(), which I think was implemented for both, but if it isn't for DMDA, its trivial and we should do it.<br>
> <br>
> Parallel, does the user need to know which process the points are on or is that all figured out?<br>
> <br>
> That is figured out. Actually, its most of the reason that this exists. However, I wrote this a long time ago. It should go away in favor of DMSwarm.<br>
> <br>
> 4) Points to a DM. Is this supported (should be?) by DMSWARM? In fact should 3) work with DMSWARM as the set of points and not have its own construct (DMInterpolationInfo)?<br>
> <br>
> This is supported. However, what is currently in there is custom code Dave wrote which only works for P1. We now have code<br>
> that does this for any element and in all dimensions. Its in a branch and will get merged shortly (next week) since it passes all<br>
> tests. However, we need some more time to fully integrate it into the interface currently in DMSwarm.<br>
> <br>
> Another problem is that Dave has a different definition of points than the plasma people. We need a nice way<br>
> to switch between these perspectives when doing interpolation, which is what will take us a little time when we are integrating.<br>
> <br>
> 5) Points to points? (Done indirectly by interpolating to a DM then back to the other points)?<br>
> <br>
> Yes, that is how I would do it.<br>
> <br>
> There is a routine DMPlexInterpolate() is this mis-named/confusing thing? Interpolate seems to mean something slight different here.<br>
> <br>
> Yes. Unfortunately, the same word is used by topology people. I am willing to change this since very few people use it, when they do its<br>
> only used once, and its completely different. It refers to figuring out the edges and faces automatically in a mesh when you get only cells<br>
> and vertices. Better name?<br>
> <br>
> Thanks,<br>
> <br>
> Matt<br>
> <br>
> All of this explanation could go into the users manual (or FAQ for now).<br>
> <br>
> Thanks for any explanations,<br>
> <br>
> Barry<br>
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> -- <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>
> <br>
> <a href="https://www.cse.buffalo.edu/~knepley/" rel="noreferrer" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>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</div><div><br></div><div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>