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Matt<br>
<br>
Any linear 2/3d element would do. A linear tetrahedron would be good
to start with.<br>
<br>
Thanks<br>
Tabrez<br>
<br>
On 05/17/2011 11:21 AM, Matthew Knepley wrote:
<blockquote
cite="mid:BANLkTi=wPPSD7y9eHM74EQmu7nbur55Mhg@mail.gmail.com"
type="cite">On Tue, May 17, 2011 at 9:36 AM, Tabrez Ali <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:stali@geology.wisc.edu">stali@geology.wisc.edu</a>></span>
wrote:<br>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div text="#000000" bgcolor="#ffffff"> Matt<br>
<br>
An example which reads an unstructured mesh (ascii or
exodus), partitions it and sets up Mat (with the right
preallocation) would be great. If it is in Fortran then that
would be perfect. Btw my problem also has Lagrange
multiplier constraints.<br>
</div>
</blockquote>
<div><br>
</div>
<div>Yes, I should have been more specific. What element?</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div text="#000000" bgcolor="#ffffff"> Thanks<br>
<font color="#888888"> Tabrez</font>
<div>
<div class="h5"><br>
<br>
On 05/17/2011 08:25 AM, Matthew Knepley wrote:
<blockquote type="cite">On Mon, May 2, 2011 at 8:16 AM,
Tabrez Ali <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:stali@geology.wisc.edu"
target="_blank">stali@geology.wisc.edu</a>></span>
wrote:<br>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin: 0pt
0pt 0pt 0.8ex; border-left: 1px solid rgb(204,
204, 204); padding-left: 1ex;">
<div text="#000000" bgcolor="#ffffff"> Is there a
way I can use this and other mesh routines from
Fortran? The manual doesn't say much on this.</div>
</blockquote>
<div><br>
</div>
<div>Yes, but you are right that nothing is in the
manual. DMMESH (in petsc-dev) now obeys the full
DM interface,</div>
<div>so that DMGetMatrix() will return you a
properly allocated Mat. So what is the problem? Of
course, it is that</div>
<div>Petsc has no good way to specify what finite
element you are dealing with.</div>
<div><br>
</div>
<div>The way I was doing this is to encode it using
some C++ classes. This turns out to be a bad way
to do things.</div>
<div> I am currently reworking it so that this
information is stored in a simple C struct that
you can produce. Should</div>
<div>have this done soon.</div>
<div><br>
</div>
<div>Can you mail me a description of an example you
would like to run?</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin: 0pt
0pt 0pt 0.8ex; border-left: 1px solid rgb(204,
204, 204); padding-left: 1ex;">
<div text="#000000" bgcolor="#ffffff"> <font
color="#888888"><br>
Tabrez</font>
<div>
<div><br>
<br>
On 05/01/2011 09:53 AM, Matthew Knepley
wrote:
<blockquote type="cite">On Sat, Apr 30, 2011
at 12:58 PM, Tabrez Ali <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:stali@geology.wisc.edu"
target="_blank">stali@geology.wisc.edu</a>></span>
wrote:<br>
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="margin: 0pt 0pt 0pt 0.8ex;
border-left: 1px solid rgb(204, 204,
204); padding-left: 1ex;"> Petsc
Developers/Users<br>
<br>
I having some performance issues with
preallocation in a fully unstructured
FE code. It would be very helpful if
those using FE codes can comment.<br>
<br>
For a problem of size 100K nodes and
600K tet elements (on 1 cpu)<br>
<br>
1. If I calculate the _exact_ number
of non-zeros per row (using a running
list in Fortran) by looping over nodes
& elements, the code takes 17 mins
(to calculate nnz's/per row, assemble
and solve).<br>
2. If I dont use a running list and
simply get the average of the max
number of nodes a node might be
connected to (again by looping over
nodes & elements but not using a
running list) then it takes 8 mins<br>
3. If I just magically guess the right
value calculated in 2 and use that as
average nnz per row then it only takes
25 secs.<br>
<br>
Basically in all cases Assembly and
Solve are very fast (few seconds) but
the nnz calculation itself (in 2 and
3) takes a long time. How can this be
cut down? Is there a heuristic way to
estimate the number (as done in 3)
even if it slightly overestimates the
nnz's per row or are efficient ways to
do step 1 or 2. Right now I have do
i=1,num_nodes; do j=1,num_elements ...
which obviously is slow for large
number of nodes/elements.<br>
</blockquote>
<div><br>
</div>
<div>If you want to see my code doing
this, look at</div>
<div><br>
</div>
<div> include/petscdmmesh.hh:preallocateOperatorNew()</div>
<div><br>
</div>
<div>which handles the determination of
nonzero structure for a FEM operator.
It should look mostly</div>
<div>like your own code.</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote"
style="margin: 0pt 0pt 0pt 0.8ex;
border-left: 1px solid rgb(204, 204,
204); padding-left: 1ex;"> Thanks in
advance<br>
<font color="#888888"> Tabrez<br>
</font></blockquote>
</div>
<br>
<br clear="all">
<br>
-- <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>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <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>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <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>
</blockquote>
<br>
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