On Mon, Apr 2, 2012 at 10:11 AM, Xuefeng Li <span dir="ltr"><<a href="mailto:li@loyno.edu">li@loyno.edu</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi, all.<br>
<br>
I am using multigrid with DMMG (5 levels) in my petsc program.<br>
Turning on the dmmg_grid_sequence option seems<br>
to slow down the program dramatically. For instance,<br>
the program converges in 3 iterations in 6.270e+01 sec<br>
when dmmg_grid_sequence is OFF; it also converges<br>
in 3 iterations but in 1.699e+04 sec when dmmg_grid_sequence<br>
is ON.<br>
<br>
Is this typical of petsc (I'm using petsc-3.1-p8)?<br>
Are there ways to improve the performance when<br>
dmmg_grid_sequence is ON?<br></blockquote><div><br></div><div>Its impossible to know what is happening from this description. There is no</div><div>"generic" performance of grid sequencing. The best thing I can say to this is,</div>
<div>it looks like the interpolated solution to your coarse problem is not a great</div><div>solution to your fine problem. However, you could be oversolving the coarse</div><div>problems, blowing up the work, or interpolating badly for your problem.</div>
<div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Regards,<br>
<br>
--Xuefeng Li, <a href="tel:%28504%29865-3340" value="+15048653340" target="_blank">(504)865-3340</a>(phone)<br>
Like floating clouds, the heart rests easy<br>
Like flowing water, the spirit stays free<br>
<a href="http://www.loyno.edu/~li/home" target="_blank">http://www.loyno.edu/~li/home</a><br>
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<br>
</blockquote></div><br><br clear="all"><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>