<div dir="ltr">Let me just add that we (me and Toby (p4est)) think of tensor grids for kinetic problems. A (phase space) grid at every spatial grid point. THis allows us to compose our existing 3D grids to get 6D, for instance. This work well/easily for Valsov-Maxwell because there are only grad_x and grad_v terms.<div><br></div><div>I have explored this with a Vlasov code and worked some of it out. We have a pretty good idea of what to do but it needs work.</div><div><br></div><div>So we are moving with the new Plex abstraction and DMDA not in our plans. I like Plex, it abstracts the grid from the numerics nicely. The only bad thing about it is that stencil methods are not natural (at all). So you, for instance, compute fluxes and then divergences, instead of composing them on paper to create a stencil.</div><div><br></div><div>Mark</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Oct 17, 2017 at 2:54 PM, 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 dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class="">On Tue, Oct 17, 2017 at 2:51 PM, Hittinger, Jeffrey A. F. <span dir="ltr"><<a href="mailto:hittinger1@llnl.gov" target="_blank">hittinger1@llnl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal">Matt - Never is a very strong word. Don’t underestimate the power of mappings and/or AMR. Also, sparse grid techniques haven’t (yet) proven to be particularly useful for kinetic problems.</p></div></div></blockquote><div><br></div></span><div>None of the above is wrong, but I really meant "regular grids in high dimension". DMDA will never do AMR or sparse grids since its designed</div><div>to be the simplest thing possible. For AMR we are using p4est, and that could definitely work in higher dimensions. I have read the Irene Gamba</div><div>stuff on Boltzmann Transport using higher-D regular grids, but its just tremendously expensive, and they really play up spectral convergence,</div><div>which relies on regularity which is often not there in practical problems.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div><div class="h5"><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="white" lang="EN-US"><div class="m_-7237041310527883211gmail-m_8795958808222375419WordSection1"><p class="MsoNormal"> </p><p class="MsoNormal"><u></u></p>
<p class="MsoNormal">Thanks for the quick response.<u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;color:black">Jeffrey A. F. Hittinger<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;color:black">Center for Applied Scientific Computing<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;color:black">Office: <a href="tel:(925)%20422-0993" value="+19254220993" target="_blank">(925) 422-0993</a><u></u><u></u></span></p>
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<p class="MsoNormal" style="margin-left:0.5in"><b><span style="font-size:12pt;color:black">From:
</span></b><span style="font-size:12pt;color:black">Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>><br>
<b>Date: </b>Tuesday, October 17, 2017 at 11:42 AM<br>
<b>To: </b>Barry Smith <<a href="mailto:bsmith@mcs.anl.gov" target="_blank">bsmith@mcs.anl.gov</a>><br>
<b>Cc: </b>Undisclosed recipients <<a href="mailto:hittinger1@llnl.gov" target="_blank">hittinger1@llnl.gov</a>>, "<a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a>" <<a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a>><br>
<b>Subject: </b>Re: [petsc-users] High-dimensional DMDA<u></u><u></u></span></p>
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<p class="MsoNormal" style="margin-left:0.5in">On Tue, Oct 17, 2017 at 2:32 PM, Barry Smith <<a href="mailto:bsmith@mcs.anl.gov" target="_blank">bsmith@mcs.anl.gov</a>> wrote:<u></u><u></u></p>
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No and it is highly unlikely to appear (the 3d code is already too complicated and we tried to write a dimension independent version but that failed)<br>
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But note that by using a dof argument > 1 one can handle some "4d" problems so long as one does no parallelize in the 4th dimension.<u></u><u></u></p>
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<p class="MsoNormal" style="margin-left:0.5in">History: We did have a version for arbitrary dimension called ADDA written by a student of David Keyes, that exists<u></u><u></u></p>
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<p class="MsoNormal" style="margin-left:0.5in">in the bowels of Git. We are unlikely to replicate it because regular grids in high dimension never seem like the right<u></u><u></u></p>
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<p class="MsoNormal" style="margin-left:0.5in">thing to do.<u></u><u></u></p>
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<p class="MsoNormal" style="margin-left:0.5in"> Thanks,<u></u><u></u></p>
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<p class="MsoNormal" style="margin-left:0.5in"> Matt<u></u><u></u></p>
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<span class="m_-7237041310527883211gmail-m_8795958808222375419hoenzb"> Barry</span></span><u></u><u></u></p>
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> On Oct 17, 2017, at 1:15 PM, Hittinger, Jeffrey A. F. <<a href="mailto:hittinger1@llnl.gov" target="_blank">hittinger1@llnl.gov</a>> wrote:<br>
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> Quick question: is there a version of the DMDA structured grid interface that supports dimensions higher than 3?<br>
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> j-<br>
> -.-- -.-- --..<br>
> Jeffrey A. F. Hittinger<br>
> Center for Applied Scientific Computing<br>
> Lawrence Livermore National Laboratory<br>
> Office: <a href="tel:%28925%29%20422-0993" target="_blank">(925) 422-0993</a><br>
> FAX: <a href="tel:%28925%29%20423-2993" target="_blank">(925) 423-2993</a><u></u><u></u></p>
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</blockquote></div></div></div><div><div class="h5"><br><br clear="all"><div><br></div>-- <br><div class="m_-7237041310527883211gmail_signature"><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.caam.rice.edu/~mk51/" target="_blank">https://www.cse.buffalo.edu/~<wbr>knepley/</a><br></div></div></div></div></div>
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