No.<br><br><div class="gmail_quote">On Mon, Dec 14, 2009 at 9:40 AM, Jarunan Panyasantisuk <span dir="ltr"><<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Thank you. I see it.<br>
I also see in the output file that sometimes the initial residual<br>
||r_0|| = ||b|| is simply rnorm ||r|| �at iteration 0. Does it change<br>
the reference during the computation?<br>
<br>
Jarunan<br>
<div class="im"><br>
<br>
Matthew Knepley wrote:<br>
> You can see in the info output what is happening. The test is<br>
><br>
> � rnorm >= ksp->divtol*ksp->rnorm0<br>
><br>
> Here ||r_0|| = ||b|| = 0.00331536 and ||r|| = 513.979, and thus it results<br>
> in divergence. It appears that ILU(0) is very bad for this problem.<br>
><br>
> � �Matt<br>
><br>
> On Mon, Dec 14, 2009 at 9:07 AM, <<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a><br>
</div><div class="im">> <mailto:<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a>>> wrote:<br>
><br>
> � � Hi,<br>
><br>
> � � Thank you for your advice. With this mail I attach the output file<br>
> � � run.log.<br>
> � � My grid is 2-level grid. The coarse grid is computed first then<br>
> � � the fine grid. The problem occur in the fine grid. You can see at<br>
> � � lines 3098, 4552 and 6127 where it is diverged.<br>
><br>
> � � Regards,<br>
> � � Jarunan<br>
><br>
><br>
><br>
> � � Quoting Matthew Knepley <<a href="mailto:knepley@gmail.com">knepley@gmail.com</a><br>
</div>> � � <mailto:<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>>>:<br>
<div class="im">><br>
> � � � � Run with -ksp_view -ksp_monitor -info and send us all the output.<br>
><br>
> � � � � �Matt<br>
><br>
> � � � � On Mon, Dec 14, 2009 at 8:36 AM, <<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a><br>
</div><div><div></div><div class="h5">> � � � � <mailto:<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a>>> wrote:<br>
><br>
><br>
> � � � � � � Dear Petsc Team,<br>
><br>
> � � � � � � There is something not clear for me about divergence<br>
> � � � � � � tolerance. Firstly, my<br>
> � � � � � � computation diverges with the reason of dtol (-4), which<br>
> � � � � � � was set by default<br>
> � � � � � � (10000). When I increased dtol to 1.0e+8, it became<br>
> � � � � � � converged. However, the<br>
> � � � � � � relative residual where it was diverged is less than the<br>
> � � � � � � default dtol. I<br>
> � � � � � � would like to know, how it is exactly calculated.<br>
><br>
> � � � � � � ----------I describe my problem more in detail<br>
> � � � � � � here.-------------------<br>
> � � � � � � As I set the tolerances for the solver as below, my<br>
> � � � � � � problem diverges with<br>
> � � � � � � converged reason -4 (from divergence tolerance)<br>
><br>
> � � � � � � call KSPSetTolerances(ksp,1.0e-06,1.0e-20,<br>
> � � � � � � PETSC_DEFAULT_DOUBLE_PRECISION,10000,ierr)<br>
><br>
> � � � � � � I monitor the residual. it printed the information below<br>
> � � � � � � and quit the<br>
> � � � � � � computation.(I delete the true residual norm and Ax/Ae.<br>
> � � � � � � Please tell me if<br>
> � � � � � � you need them.)<br>
><br>
> � � � � � � �0 KSP preconditioned resid norm 5.139790011051e+02<br>
><br>
> � � � � � � With -ksp_view, it shows that default value of dtol is<br>
> � � � � � � 10000. I increased<br>
> � � � � � � dtol to 1.0e+8, then the solver solved the problem. With<br>
> � � � � � � -ksp_monitor_true_residual, the first 5 iterations read:<br>
><br>
> � � � � � � �0 KSP preconditioned resid norm 5.139790011051e+02<br>
> � � � � � � �1 KSP preconditioned resid norm 1.840751662590e+01<br>
> � � � � � � �2 KSP preconditioned resid norm 3.653339750400e+00<br>
> � � � � � � �3 KSP preconditioned resid norm 2.538794826933e+00<br>
> � � � � � � �4 KSP preconditioned resid norm 2.299844715275e-01<br>
><br>
> � � � � � � Here, from iteration 0 to iteration 1,the relative<br>
> � � � � � � residual is 0.03580,<br>
> � � � � � � much less than 1.0e+4 the default dtol value. So, why was<br>
> � � � � � � it diverged at the<br>
> � � � � � � first time?<br>
><br>
> � � � � � � ----------------------------------------------------------------------------<br>
><br>
> � � � � � � Regards,<br>
> � � � � � � Jarunan<br>
><br>
><br>
><br>
><br>
> � � � � � � --<br>
> � � � � � � Jarunan Panyasantisuk<br>
> � � � � � � Development Engineer<br>
> � � � � � � ASCOMP GmbH, Technoparkstr. 1<br>
> � � � � � � CH-8005 Zurich, Switzerland<br>
> � � � � � � Phone : +41 44 445 4072<br>
> � � � � � � Fax � : +41 44 445 4075<br>
</div></div>> � � � � � � E-mail: <a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a> <mailto:<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a>><br>
> � � � � � � <a href="http://www.ascomp.ch" target="_blank">www.ascomp.ch</a> <<a href="http://www.ascomp.ch" target="_blank">http://www.ascomp.ch</a>><br>
<div class="im">><br>
><br>
><br>
><br>
> � � � � --<br>
> � � � � What most experimenters take for granted before they begin<br>
> � � � � their experiments<br>
> � � � � is infinitely more interesting than any results to which their<br>
> � � � � experiments<br>
> � � � � lead.<br>
> � � � � -- Norbert Wiener<br>
><br>
><br>
><br>
><br>
> � � --<br>
> � � Jarunan Panyasantisuk<br>
> � � Development Engineer<br>
> � � ASCOMP GmbH, Technoparkstr. 1<br>
> � � CH-8005 Zurich, Switzerland<br>
> � � Phone : +41 44 445 4072<br>
> � � Fax � : +41 44 445 4075<br>
</div>> � � E-mail: <a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a> <mailto:<a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a>><br>
> � � <a href="http://www.ascomp.ch" target="_blank">www.ascomp.ch</a> <<a href="http://www.ascomp.ch" target="_blank">http://www.ascomp.ch</a>><br>
<div><div></div><div class="h5">><br>
><br>
><br>
><br>
> --<br>
> What most experimenters take for granted before they begin their<br>
> experiments is infinitely more interesting than any results to which<br>
> their experiments lead.<br>
> -- Norbert Wiener<br>
<br>
<br>
--<br>
Jarunan Panyasantisuk<br>
Development Engineer<br>
ASCOMP GmbH, Technoparkstr. 1<br>
CH-8005 Zurich, Switzerland<br>
Phone : +41 44 445 4072<br>
Fax � : +41 44 445 4075<br>
E-mail: <a href="mailto:jarunan@ascomp.ch">jarunan@ascomp.ch</a><br>
<a href="http://www.ascomp.ch" target="_blank">www.ascomp.ch</a><br>
<br>
<br>
</div></div></blockquote></div><br><br clear="all"><br>-- <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>