I found that I should set up KSP in each Newton iteration ( if I don't want to use SNES I think!). <br>Then KSP linear solver converged and my problem is solved.<br>By the way, Is it correct to re-setup KSP in each Newton iteration or I can use a better way?<br>
<br><br><div class="gmail_quote">On Tue, Oct 11, 2011 at 7:45 PM, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im">On Tue, Oct 11, 2011 at 11:13 AM, behzad baghapour <span dir="ltr"><<a href="mailto:behzad.baghapour@gmail.com" target="_blank">behzad.baghapour@gmail.com</a>></span> wrote:<br></div><div class="gmail_quote">
<div class="im"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Okey. I checked the condition number "max/min".<br>It increases significantly in each ksp iterations!!!<br></blockquote><div><br></div></div><div>The approximation is becoming better. The condition number is harder to actually compute than the solution.</div>
<div><br></div><div>Bottom line: You have a hard problem. Iterative methods do not work on hard problems without specialized</div><div>preconditioners. I recommend a literature search on solvers for your equations.</div>
<div>
<br></div><div> Matt</div><div class="im"><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Is it correct when the Jacobian matrix is fixed for each ksp iterations or it is due to my fault?<br>
<br>
<div class="gmail_quote">On Tue, Oct 11, 2011 at 7:28 PM, Jed Brown <span dir="ltr"><<a href="mailto:jedbrown@mcs.anl.gov" target="_blank">jedbrown@mcs.anl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div class="gmail_quote">On Tue, Oct 11, 2011 at 10:55, behzad baghapour <span dir="ltr"><<a href="mailto:behzad.baghapour@gmail.com" target="_blank">behzad.baghapour@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
OK. Then how I can calculate and monitor the "condition number" in ksp?</blockquote></div><br></div><div>-ksp_monitor_singular_value</div>
</blockquote></div><br><font color="#888888"><br clear="all"><br>-- <br>==================================<br>Behzad Baghapour<br>Ph.D. Candidate, Mechecanical Engineering<br>University of Tehran, Tehran, Iran<br><a href="https://sites.google.com/site/behzadbaghapour" target="_blank">https://sites.google.com/site/behzadbaghapour</a><br>
Fax: 0098-21-88020741<br>==================================<br><br>
</font></blockquote></div></div><font color="#888888"><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>
</font></blockquote></div><br><br clear="all"><br>-- <br>==================================<br>Behzad Baghapour<br>Ph.D. Candidate, Mechecanical Engineering<br>University of Tehran, Tehran, Iran<br><a href="https://sites.google.com/site/behzadbaghapour" target="_blank">https://sites.google.com/site/behzadbaghapour</a><br>
Fax: 0098-21-88020741<br>==================================<br><br>