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<div>Hi</div>
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<div>I just tried Matt's suggestion and tried to guess other preconditioning options as well. I didnt have the time to think about their appropriateness.<br>
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<div>All preconditioners worked with the actual ts/ex15. gmag took 13 times longer to finish than the case when I ran without any preconditioner. The fastest was the jacobi, followed by sor and bjacobi options to -pc_type I could not guess the names of the
other listed preconditioners associated with ts and snes.<br>
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<div>In my code however, I found that sor and gamg did not work. I got error messages, and the first few lines are pasted below. My test was on 1 proc and 4 procs, both giving similar errors with differnent line numbers. The petsc part of my code is virtually
identical to the example. Any comments on what is missing or can be changed?<br>
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cheers<br>
Sanjay<br>
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[1]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------<br>
[1]PETSC ERROR: Arguments are incompatible<br>
[1]PETSC ERROR: Zero diagonal on row 39<br>
[1]PETSC ERROR: Petsc Release Version 3.5.2, unknown <br>
[1]PETSC ERROR: ./sk2d on a linux-gnu-c-debug named atriumpc.ex.ac.uk by sanjay Tue Apr 21 19:28:53 2015<br>
[1]PETSC ERROR: Configure options --with-cc=gcc --with-cxx=g++ --with-fc=gfortran --download-fblaslapack --download-mpich --download-sundials --download-scalapack --with-c2html=0<br>
[1]PETSC ERROR: #1 MatInvertDiagonal_SeqAIJ() line 1724 in /media/6c6201d2-4e2e-4b24-8d04-263b5bc06dfa/sanjay/petsc/src/mat/impls/aij/seq/aij.c<br>
[1]PETSC ERROR: #2 MatSOR_SeqAIJ() line 1756 in /media/6c6201d2-4e2e-4b24-8d04-263b5bc06dfa/sanjay/petsc/src/mat/impls/aij/seq/aij.c<br>
[1]PETSC ERROR: #3 MatSOR_MPIAIJ() line 1483 in /media/6c6201d2-4e2e-4b24-8d04-263b5bc06dfa/sanjay/petsc/src/mat/impls/aij/mpi/mpiaij.c<br>
[1]PETSC ERROR: #4 MatSOR() line 3643 in /media/6c6201d2-4e2e-4b24-8d04-263b5bc06dfa/sanjay/petsc/src/mat/interface/matrix.c<br>
[1]PETSC ERROR: #5 PCApply_SOR() line 35 in /media/6c6201d2-4e2e-4b24-8d04-263b5bc06dfa/sanjay/petsc/src/ksp/pc/impls/sor/sor.c<br>
[1]PETSC ERROR: #6 PCApply() line 440 in /media/6c6201d2-4e2e-4b24-8d04-263b5bc06dfa/sanjay/petsc/src/ksp/pc/interface/precon.c<br>
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<div id="divRpF175770" style="direction:ltr"><font color="#000000" face="Tahoma" size="2"><b>From:</b> Matthew Knepley [knepley@gmail.com]<br>
<b>Sent:</b> 21 April 2015 16:51<br>
<b>To:</b> Sanjay Kharche<br>
<b>Cc:</b> petsc-users@mcs.anl.gov<br>
<b>Subject:</b> Re: [petsc-users] preconditioning<br>
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<div class="gmail_quote">On Tue, Apr 21, 2015 at 10:49 AM, Sanjay Kharche <span dir="ltr">
<<a href="mailto:Sanjay.Kharche@manchester.ac.uk" target="_blank">Sanjay.Kharche@manchester.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
<br>
Hi<br>
<br>
I am working through the KSP examples, but I will ask for any comments in the mean time.<br>
<br>
I have a TS code for 2D/3D heat equation, starting from ts/ex15. How can I easily modify this code to include a parallel preconditioner. As of now, I just need to add a preconditioner which is easy to program. The coefficients in my systems matrix are constant,
but RHS changes at each iteration.<br>
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<div>Use -pc_type gamg. You have the Laplacian + Identity, so this should work fine.</div>
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<div> Thanks,</div>
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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">
cheers<br>
<span class="HOEnZb"><font color="#888888">Sanjay<br>
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-- <br>
<div class="gmail_signature">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</div>
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