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I noticed this thread and just wanted to point out that you need to
be careful with what you use these singular values for. In my own
(limited) experience, I seem to recall finding that the singular
values you get from the Hessenberg matrix in GMRES are pretty
inaccurate. Your mileage may vary.<br>
<br>
--Richard<br>
<br>
On 10/20/2011 10:38 AM, Jed Brown wrote:
<blockquote
cite="mid:CAM9tzSkLcRCpMJEWonQisV9m=AyqqrhZVYWtkyjBuSPJBesWWg@mail.gmail.com"
type="cite">
<div class="gmail_quote">On Thu, Oct 20, 2011 at 09:34, Klaij,
Christiaan <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:C.Klaij@marin.nl">C.Klaij@marin.nl</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":3gt">call
KSPMonitorSet(ksp,KSPMonitorSingularValue,PETSC_NULL,PETSC_NULL,ierr);<br>
</div>
</blockquote>
<div><br>
</div>
<div>This gets KSPMonitorSingularValue called after each
iteration. That routine prints the singular values.</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":3gt">
call KSPSetComputeSingularValues(ksp,PETSC_TRUE,ierr)<br>
</div>
</blockquote>
<div><br>
</div>
<div>This instructs the KSP to save the extra information needed
by the monitor above.</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":3gt">
<br>
in the part where I initialize the KSP. But where to call<br>
KSPMonitorSingularValue? And how do I get "n" and "rnorm"?<br>
</div>
</blockquote>
</div>
<br>
<div>Do you want a monitor or do you want to extract estimates of
the singular values after KSPSolve has converged? You might be
interested in KSPComputeExtremeSingularValues(), for example.</div>
</blockquote>
<br>
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