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<div class="moz-cite-prefix">Hi Matt,<br>
<br>
Have you had a chance to think about the cell overlap problem? I'm
proposing to make the center dimension a general Plex attribute
with the current behaviour as the default. We can then generate
the cell overlap in DMPlexDistribute according to the center
dimension using a utility function for point adjacency, something
like DMPlexGetAdjacentPoints(dm, p). <br>
<br>
I'm happy to provide a pull request for this change, just tell me
if you agree with this approach or if you see any problems.<br>
<br>
Thanks and kind regards,<br>
<br>
Michael<br>
<br>
<br>
On 03/02/14 11:32, Michael Lange wrote:<br>
</div>
<blockquote cite="mid:52EF7E36.7040403@imperial.ac.uk" type="cite">
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<div class="moz-cite-prefix">Hi Matt,<br>
<br>
On 31/01/14 05:11, Matthew Knepley wrote:<br>
</div>
<blockquote
cite="mid:CAMYG4GkfpViWZ2=+b4Dr7hnNTDrCrjjYPm5aHQJSL1g8np9Lcw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">On Tue, Jan 28, 2014 at 8:57 AM,
Michael Lange <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:michael.lange@imperial.ac.uk"
target="_blank">michael.lange@imperial.ac.uk</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
I noticed that the cell overlap created during
DMPlexDistribute does not include cells that only share
a vertex but no edge with an owned cell. This causes
problems when performing local assembly
(MAT_IGNORE_OFF_PROC_ENTRIES) based on information from
the plex, because one contribution to the shared vertex
is missing.<br>
<br>
As an example consider the 2x2 square with 8 cells
(attached). When partitioned across two ranks with
overlap=1 each rank owns 4 cells and in the current
version knows about 2 halo cells, giving a total of 6
cells. The central vertex, however, touches 3 owned and
3 non-owned cells, one of which doesn't share an edge
with any owned cells. So, in order to correctly assemble
the central vertex locally, the rank owning it needs to
know about 7 cells in total.<br>
<br>
I have attached a patch that fixes this problem by going
over the inverse closure of all vertices associated with
a given cell instead of using the provided edge graph.
Please tell me what you think and whether there might be
an easier way to fix this.<br>
</blockquote>
<div><br>
</div>
<div>This is true, but unfortunately not what everyone
wants. FVM people want just what is there now. This</div>
<div>same choice comes up in preallocation. There I have
put in the "center dimension" which says what</div>
<div>kind of point do you use for the center, vertex or
face? I guess we need that here as well.</div>
</div>
</div>
</div>
</blockquote>
Yes, I think the center dimension is exactly what we need here,
because my proposed fix is to switch from using star(cone(p)) to
star(closure(p)). So, do you want to make the center dimension a
general Plex attribute and move the Set/Get functions to plex.c?
If so, what would be the default? In that case a
DMPlexGetAdjacentPoints(dm, p) function might also be helpful if
this is used in several places? I'm happy to provide a pull
request, just tell me how you want this to be structured. <br>
<br>
Thanks<br>
Michael<br>
</blockquote>
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