<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">This is in GMRES, I would check for a zero on the diagonal.<div><br><div><div>On Sep 15, 2012, at 3:16 AM, TAY wee-beng <<a href="mailto:zonexo@gmail.com">zonexo@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div class="moz-cite-prefix">On 14/9/2012 4:38 PM, Mark F. Adams
wrote:<br>
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<blockquote cite="mid:8BEF4C19-0C76-454E-800A-10265A272A25@columbia.edu" type="cite">
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<div>On Sep 14, 2012, at 8:47 AM, Jed Brown <<a moz-do-not-send="true" href="mailto:jedbrown@mcs.anl.gov">jedbrown@mcs.anl.gov</a>>
wrote:</div>
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<blockquote type="cite">
<div class="gmail_quote">On Fri, Sep 14, 2012 at 3:47 AM, TAY
wee-beng <span dir="ltr"><<a moz-do-not-send="true" href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
<br>
I need to solve the Poisson eqn on my win7 machine. I'm
currently using BCGS without preconditioner. I can't use
HYPRE since I'm using Fortran and win7. It's rather slow.<br>
<br>
Is there a recommended solver and preconditioner to solve
the Poisson eqn to get me started?<br>
</blockquote>
<div><br>
</div>
<div>What discretization?</div>
<div><br>
</div>
<div>Run with -pc_type gamg to start.</div>
</div>
</blockquote>
<br>
</div>
<div>and </div>
<div><br>
</div>
<div>-pc_gamg_agg_nsmooths 1</div>
</blockquote>
<br>
I am using non-uniform Cartesian grid to solve. What do you mean by
the discretization? I 'm using finite volume method to obtain a
system of linear eqns.<br>
<br>
I tried both -pc_type gamg and -pc_gamg_agg_nsmooths 1 but the
solver breaks down. The error msg is:<br>
<br>
<i>[0]PETSC ERROR:
------------------------------------------------------------------------</i><i><br>
</i><i>[0]PETSC ERROR: Caught signal number 8 FPE: Floating Point
Exception,probably divide by zero</i><i><br>
</i><i>[0]PETSC ERROR: Try option -start_in_debugger or
-on_error_attach_debugger</i><i><br>
</i><i>[0]PETSC ERROR: or see
<a class="moz-txt-link-freetext" href="http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind">http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind</a>[0]PETSC
ERROR: or try <a class="moz-txt-link-freetext" href="http://valgrind.org/">http://valgrind.org</a> on GNU/linux and Apple Mac OS X
to find memory corruption errors</i><i><br>
</i><i>[0]PETSC ERROR: likely location of problem given in stack
below</i><i><br>
</i><i>[0]PETSC ERROR: --------------------- Stack Frames
------------------------------------</i><i><br>
</i><i>[0]PETSC ERROR: Note: The EXACT line numbers in the stack are
not available,</i><i><br>
</i><i>[0]PETSC ERROR: INSTEAD the line number of the start of
the function</i><i><br>
</i><i>[0]PETSC ERROR: is given.</i><i><br>
</i><i>[0]PETSC ERROR: [0] KSPComputeExtremeSingularValues_GMRES
line 24
src/ksp/ksp/impls/gmres/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\ksp\impls\gmres\gmreig.c</i><i><br>
</i><i>[0]PETSC ERROR: [0] KSPComputeExtremeSingularValues line 40
src/ksp/ksp/interface/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\ksp\INTERF~1\itfunc.c</i><i><br>
</i><i>[0]PETSC ERROR: [0] PCGAMGOptprol_AGG line 1294
src/ksp/pc/impls/gamg/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\pc\impls\gamg\agg.c</i><i><br>
</i><i>[0]PETSC ERROR: [0] PCSetUp_GAMG line 559
src/ksp/pc/impls/gamg/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\pc\impls\gamg\gamg.c</i><i><br>
</i><i>[0]PETSC ERROR: [0] PCSetUp line 810
src/ksp/pc/interface/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\pc\INTERF~1\precon.c</i><i><br>
</i><i>[0]PETSC ERROR: [0] KSPSetUp line 182
src/ksp/ksp/interface/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\ksp\INTERF~1\itfunc.c</i><i><br>
</i><i>[0]PETSC ERROR: [0] KSPSolve line 351
src/ksp/ksp/interface/C:\wtay\DOWNLO~1\Codes\PETSC-~1\src\ksp\ksp\INTERF~1\itfunc.c</i><i><br>
</i><i>[0]PETSC ERROR: --------------------- Error Message
------------------------------------</i><i><br>
</i><i>[0]PETSC ERROR: Signal received!</i><i><br>
</i><i>[0]PETSC ERROR:
------------------------------------------------------------------------</i><i><br>
</i><i>[0]PETSC ERROR: Petsc Development HG revision:
d560f272ff1b6e7f4e28667ab8b55f0c7408979e HG Date: Wed Jul 25
14:42:03 2012 -0500</i><i><br>
</i><i>[0]PETSC ERROR: See docs/changes/index.html for recent
updates.</i><i><br>
</i><i>[0]PETSC ERROR: See docs/faq.html for hints about trouble
shooting.</i><i><br>
</i><i>[0]PETSC ERROR: See docs/index.html for manual pages.</i><i><br>
</i><i>[0]PETSC ERROR:
------------------------------------------------------------------------</i><i><br>
</i><i>[0]PETSC ERROR:
C:\Obj_tmp\ibm3d_high_Re_staggered_AB2\Debug\ibm3d_high_Re_staggered_AB2.exe
on a petsc-3.3 named USER-PC by User Sat Sep 15 09:12:58 2012</i><i><br>
</i><i>[0]PETSC ERROR: Libraries linked from
/cygdrive/d/wtay/Lib/petsc-3.3-dev_win32_vs2008/lib</i><i><br>
</i><i>[0]PETSC ERROR: Configure run at Thu Jul 26 11:01:27 2012</i><i><br>
</i><i>[0]PETSC ERROR: Configure options --with-cc="win32fe cl"
--with-fc="win32fe ifort" --with-cxx="win32fe cl"
--with-mpi-dir=/cygdrive/c/MPICH2/ --download-f-blas-lapack=1
--prefix=/cygdrive/d/wtay/Lib/petsc-3.3-dev_win32_vs2008
--with-debugging=1 --useThreads=0</i><i><br>
</i><i>[0]PETSC ERROR:
------------------------------------------------------------------------</i><i><br>
</i><i>[0]PETSC ERROR: User provided function() line 0 in unknown
directory unknown file</i><i><br>
</i><i>application called MPI_Abort(MPI_COMM_WORLD, 59) - process 0</i><br>
<br>
Btw, I've used both GMRES and BCGS as the ksp. What other options
can I try?<br>
<br>
Thanks<br>
<blockquote cite="mid:8BEF4C19-0C76-454E-800A-10265A272A25@columbia.edu" type="cite">
<div><br>
</div>
<div>(I should make this the default)</div>
<div><br>
</div>
<div>Mark</div>
<br>
</blockquote>
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</blockquote></div><br></div></body></html>