<div dir="ltr"><div class="gmail_quote"><div dir="ltr">On Sat, Jan 5, 2019 at 4:04 AM Yann Jobic <<a href="mailto:yann.jobic@univ-amu.fr">yann.jobic@univ-amu.fr</a>> wrote:<br></div><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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<div class="gmail-m_-6168566035861119409moz-cite-prefix">On 05/01/2019 02:36, Matthew Knepley
wrote:<br>
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<div dir="ltr">On Fri, Jan 4, 2019 at 10:04 AM Yann Jobic via
petsc-users <<a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Dear Petsc Users,<br>
<br>
I'm using DMPlexCreateFromCellList to create my DM. I would
like to have <br>
an order 2 geometry.<br>
<br>
It's working fine in 2D for elements of type Q9.<br>
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<div>I do not see how that is possible. The topology does not
work that way, and there</div>
<div>is no way a 9 vertex quad was interpolated, so something
else is happening.</div>
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<div>Moreover, anything you input still has affine geometry.
Toby has been working on</div>
<div>non-affine geometry, and all the code is there, but right
now you have to build and</div>
<div>populate the coordinate space by hand. What this means is
that you create a</div>
<div>quadratic space for the coordinate DM (rather than the
default linear), get the</div>
<div>global coordinate vector out, and stick in the Q9
coordinates. The topology is still</div>
<div>the same no matter what coordinates you read in.</div>
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<p>I get the idea. So at the beginning i start with the Q4/H8
dmplex, then i fill from the global coordinate vector the missing
coordinates, and attach this new coordinate vector to the DM.</p></div></blockquote><div>Yes. <br></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="#FFFFFF"><p>Then
the interpolation will be correct ?</p></div></blockquote><div>This is the tricky part. What you likely have to do is:</div><div><br></div><div> 1) Build the topology</div><div> 2) Run over the cells</div><div> 3) For each cell, put in the coordinates using DMPlexVecSetClosure(). This is redundant, but the only way<br></div><div> you can connect with the Q9 format.</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="#FFFFFF"><p> Can i use DMproject and all
the petsc functions ? <br></p></div></blockquote><div>This is the idea. The amount of testing is so far almost nothing. </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="#FFFFFF"><p>
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<p>In order to output the results, i've got to write my own vtk
interface no ? (by splitting the Q9/H27 in 4xQ4 or 8xH8).</p></div></blockquote><div>That is a good question. Right now, it will just output Q4. However, compared to everything else, writing Q9 should</div><div>be comparatively easy. </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="#FFFFFF">
<p>Or is it working with the hdf5 one ?</p></div></blockquote><div>I would probably write code to to Xdmf through HDF5 rather than straight VTK, but we will end up having both.</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="#FFFFFF">
<p>Does the p4est interface work with this setup ?</p></div></blockquote><div>It will. I do not know if it currently does. We have to check.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt </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="#FFFFFF">
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<div>We will get around to making an interface for this soon.</div>
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<p>Great ! <br>
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<p>Thanks,</p>
<p>Yann<br>
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<div> Thanks,</div>
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<div> Matt</div>
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I checked that it's working correctly by using <br>
DMPlexComputeCellGeometryFEM, and compute the value of the
determinant <br>
(CheckMeshGeometry of
dm/impls/plex/examples/tutorials/ex2.c)<br>
<br>
I can import H8 elements, it's working fine.<br>
<br>
But for H27 element, it's not working. I really don't know
how to order <br>
my vertex in the cells array. So far, the determinant is
zero...<br>
<br>
I don't know where to look in order to find this
information. I tried <br>
the function DMPlexGetRawFaces_Internal of the file<br>
<br>
<a href="https://www.mcs.anl.gov/petsc/petsc-current/src/dm/impls/plex/plexinterpolate.c.html#DMPlexGetRawFaces_Internal" rel="noreferrer" target="_blank">https://www.mcs.anl.gov/petsc/petsc-current/src/dm/impls/plex/plexinterpolate.c.html#DMPlexGetRawFaces_Internal</a><br>
<br>
but it didn't help me.<br>
<br>
Could you please point me where to look ?<br>
<br>
Thanks, and happy new year !<br>
<br>
Yann<br>
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<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>
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<div><a href="http://www.cse.buffalo.edu/~knepley/" 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"><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>