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<div class="moz-cite-prefix">Hi Matt,<br>
<br>
Are there any updates on this?<br>
<br>
Thanks,<br>
<br>
Michael<br>
<br>
On 23/02/14 20:50, Matthew Knepley wrote:<br>
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<div class="gmail_quote">On Fri, Feb 21, 2014 at 6:56 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>
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<div>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>
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<div><br>
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<div>Yes, you are correct in this. We are having another
discussion on petsc-maint about the kinds of partitions
that are</div>
<div>appropriate for different problems. I will try and get
through this as quickly as I can, and I will solicit your
feedback</div>
<div>when I get the plan for implementation done.</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
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<div> Thanks and kind regards,<br>
<br>
Michael
<div>
<div class="h5"><br>
<br>
<br>
On 03/02/14 11:32, Michael Lange wrote:<br>
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<div>Hi Matt,<br>
<br>
On 31/01/14 05:11, Matthew Knepley wrote:<br>
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<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>
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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>
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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
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