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On 13.06.2012 13:24, Matthew Knepley wrote:
<blockquote
cite="mid:CAMYG4Gk20ohOBM0DfKXK0+7NO2RhGN3ukQBX+osXqXM3rCq8KQ@mail.gmail.com"
type="cite">On Wed, Jun 13, 2012 at 6:45 PM, Alexander Grayver <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:agrayver@gfz-potsdam.de" target="_blank">agrayver@gfz-potsdam.de</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;">
Hello,<br>
<br>
As stated, I would like to estimate computation to
communication ratio for PETSc's linear algebra routines (e.g.
MatMult{Transpose}, MatPtAP, MatMatMult etc.)<br>
As far as I understand the ratio depends on particular
implementation and number of processes one runs application
on.<br>
So I guess these formulas should be known?<br>
</blockquote>
<div><br>
</div>
<div>It depends on the input data. For example, block diagonal
matrices do not communicate in MatMult().</div>
<div> </div>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
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If not then I see one way to estimate it. Write app with those
operations, parse -log_summary and then divide flops/messages,
however the question is what information from -log_summary
output should be used for that?<br>
</blockquote>
<div><br>
</div>
<div>We give the number of messages and the average message
length, so you can get the total length across processes.
Since</div>
<div>each side records, we divide by 2 (I think, you should
check PetscLogView for specifics). You can also use
PetscLogViewPython()</div>
<div>to simplify parsing.</div>
</div>
</blockquote>
<br>
Is there total amount of flops given for different operations
separately (I see max flops over all processes only)?<br>
<br>
<blockquote
cite="mid:CAMYG4Gk20ohOBM0DfKXK0+7NO2RhGN3ukQBX+osXqXM3rCq8KQ@mail.gmail.com"
type="cite">
<div class="gmail_quote">
<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.<span class="HOEnZb"><font color="#888888"><br>
<br>
-- <br>
Regards,<br>
Alexander<br>
<br>
</font></span></blockquote>
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<br>
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<div><br>
</div>
-- <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>
<br>
<pre class="moz-signature" cols="72">--
Regards,
Alexander</pre>
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