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<div class="moz-cite-prefix">Thanks, exactly what I've searched for.<br>
<br>
Thomas<br>
<br>
Am 24.10.2012 22:19, schrieb Jed Brown:<br>
</div>
<blockquote
cite="mid:CAM9tzS=yym9DtFukMupksU9VvjY1tHrFEiOckxp7GszKgDoiAw@mail.gmail.com"
type="cite">You are looking for PCFieldSplitGetSubKSP().
<div><br>
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<div>Matt's comment was about distinguishing between the KSP
living inside of S = D - C A^{-1} B and the one used directly by
PCFIeldSplit when solving with A.<br>
<br>
<div class="gmail_quote">On Wed, Oct 24, 2012 at 3:04 PM, Thomas
Witkowski <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:thomas.witkowski@tu-dresden.de"
target="_blank">thomas.witkowski@tu-dresden.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>Am 24.10.2012 21:33, schrieb Matthew Knepley:<br>
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<div class="im">
<blockquote type="cite">On Wed, Oct 24, 2012 at 3:23 PM,
Thomas Witkowski <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:thomas.witkowski@tu-dresden.de"
target="_blank">thomas.witkowski@tu-dresden.de</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">
I want to play around with some special type of a
Schur complement preconditioner. It perfectly fits
into PETSc's fieldsplit preconditioner (schur -
full factorization). But for the inner solvers, I
would like to create some MatShells. So I need to
access both KSP objects, for the upper block
(KSP(A_00)) and for the Schur complement (KSP(S)).
How can I get these objects in my source code?<br>
</blockquote>
<div><br>
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<div>First you have to make them different. This
happens when you give options for</div>
<div><br>
</div>
<div> -fieldsplit_1_upper_*</div>
<div> -fieldsplit_1_inner_*</div>
<div><br>
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<div>This is how I customize the solvers to get
things like SIMPLE. Once they are created, you</div>
<div>can get them by pulling apart the FS. The upper
is fs->kspupper, and the inner is the KSP</div>
<div>from the MATSCHUR from fs->schur.</div>
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I don't understand your solution. Maybe I should put some
lines of code to emphasize my question. The relevant part
looks as follows:<br>
<br>
PCSetType(pc, PCFIELDSPLIT);<br>
PCFieldSplitSetSchurFactType(pc,
PC_FIELDSPLIT_SCHUR_FACT_FULL);<br>
...<br>
PCFieldSplitSetIS(pc, "velocity", is0);<br>
PCFieldSplitSetIS(pc, "pressure", is1);<br>
...<br>
KSP velocity;<br>
KSP schur;<br>
....<br>
<br>
Okay, I don't solve any Stokes/Navier Stokes equation, but
to make the names somehow convenient I choose here the
names velocity and pressure for the two system blocks. My
question is now, how to figure out the two inner solver
objects from the field split preconditioner. <br>
<br>
Matt, if your answer is still appropriate to my question,
can you make it clear on the above piece of code? Thank
you very much.<span class="HOEnZb"><font color="#888888"><br>
<br>
Thomas</font></span>
<div class="im"><br>
<br>
<blockquote type="cite">
<div class="gmail_quote">
<div><br>
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<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Best regards,<br>
<br>
Thomas<br>
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-- <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>
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