On Fri, May 15, 2009 at 4:23 PM, Christian May <span dir="ltr"><<a href="mailto:cmay@phys.ethz.ch">cmay@phys.ethz.ch</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
On Fri, 15 May 2009, Matthew Knepley wrote:<br>
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3) Run with -pc_type lu -ksp_type preonly first to test.<br>
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Thanks for your hints.<br>
This works fine: Linear solve converged due to CONVERGED_ITS iterations 1</blockquote><div><br>I do not think its fine. I ran with KSP ex10:<br><br>knepley@khan:/PETSc3/petsc/petsc-dev/src/ksp/ksp/examples/tutorials$ ./ex10 -f0 ~/Desktop/binaryoutput -ksp_monitor -pc_type lu -ksp_type preonly<br>
Number of iterations = 1<br>Residual norm 1.12564e+06<br><br>The huge residual says that LU bit the dust on roundoff with this matrix, which must have an astronomical<br>condition number. Do you have a good physics reason that it should be almost singular? If not, I would<br>
reformulate the problem.<br><br> Matt<br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
On Fri, 15 May 2009, Barry Smith wrote:<br>
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Could you please save this matrix and right hand side using -ksp_view_binary (just run solver like you usually do but use this command line option also) then post the file binaryoutput that is generated. This way people can trivially load the matrix and right hand side with MatLoad() and not monkey with parsing ASCII files.<br>
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Sure, I wasn't aware of this option. The file is now available at<br>
<a href="http://www.mayarea.de/download/binaryoutput" target="_blank">http://www.mayarea.de/download/binaryoutput</a><br>
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Thanks a lot<br><font color="#888888">
Christian<br></font></blockquote></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>