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On 07/22/2012 08:17 PM, Jed Brown wrote:
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<div class="gmail_quote">On Sun, Jul 22, 2012 at 1:11 PM, Umut
Tabak <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:u.tabak@tudelft.nl" target="_blank">u.tabak@tudelft.nl</a>></span>
wrote:<br>
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<div bgcolor="#FFFFFF" text="#000000">Well, basically, I am
not interested in time domain response. What I would like to
do is to find the eigenvalues/vectors of the system so it is
in the frequency domain. What I was doing it generally is
the fact that I first factorize the operator matrix with the
normal factorization operation and use it to do multiple
solves in my Block Lanczos eigenvalue solver. Then in my
performance evaluations I saw that this is the point that I
should make faster, then I realized that I could solve this
particular system, that is pinned in your words, faster with
iterative methods almost %20 percent faster. And this is the
reason why I am trying to dig under.</div>
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<div><br>
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<div>How many grid points per wavelength? <br>
</div>
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I am not sure at the moment I should check it further but the mesh
is fine enough that this should not be a problem in the frequency
range of interest.<br>
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cite="mid:CAM9tzSnj0_md5=ct6wNB6KozZ4CnP0zN+x6yD5BGom1xoPhkWQ@mail.gmail.com"
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<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">basically
the operator is singular however for my problem I
can delete one of the rows of the matrix, for this
case, I and get a non-singular operator that I can
continue my operations, basically, I am getting a
matrix with size n-1, where original problem size is
n.</blockquote>
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<div>This is often bad for iterative solvers. See the
User's Manual section on solving singular systems.
What is the condition number of the original
operator minus the zero eigenvalue (instead of
"pinning" on point)?</div>
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This is not clear to me... You mean something like
projecting the original operator on the on the zero
eigenvector, some kind of a deflation.</div>
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<br>
<div>See the User's Manual section. As long as the preconditioner
is stable, convergence is as good as for the nonsingular problem
by removing the null space on each iteration.</div>
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Ok I will see that part,<br>
Thx.<br>
U.<br>
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