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<font face="Ubuntu">Hi,<br>
<br>
I proceeded as Matt suggested. I am running without nullspace
(Dirichlet's BCs) with the following options:<br>
<br>
-pc_type gamg -pc_mg_cycle_type v -pc_gamg_agg_nsmooths 1
-mg_coarse_sub_pc_factor_shift_type NONZERO -ksp_view
-options_left<br>
<br>
The results are fine and the run finishes. The output of -ksp_view
does not say anything about the coarse solver being shifted.<br>
In fact the option </font><font face="Ubuntu"><font
face="Ubuntu">-mg_coarse_sub_pc_factor_shift_type NONZERO is not
used:<br>
<br>
#PETSc Option Table entries:<br>
-ksp_view<br>
-mg_coarse_sub_pc_factor_shift_type NONZERO<br>
-options_left<br>
-pc_gamg_agg_nsmooths 1<br>
-pc_mg_cycle_type v<br>
-pc_type gamg<br>
#End of PETSc Option Table entries<br>
There is one unused database option. It is:<br>
Option left: name:-mg_coarse_sub_pc_factor_shift_type value:
NONZERO<br>
<br>
Michele<br>
<br>
<br>
</font></font>
<div class="moz-cite-prefix">On 05/24/2013 03:20 PM, Matthew Knepley
wrote:<br>
</div>
<blockquote
cite="mid:CAMYG4Gn6MNYri+53pz5iZfvWgGm04nAPcyirPWKoTRsWCgvMmA@mail.gmail.com"
type="cite">
<div dir="ltr">On Fri, May 24, 2013 at 5:18 PM, Michele Rosso <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:mrosso@uci.edu" target="_blank">mrosso@uci.edu</a>></span>
wrote:<br>
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF"> <font
face="Ubuntu">Using <br>
<br>
-pc_type gamg -pc_mg_cycle_type v
-pc_gamg_agg_nsmooths 1
-mg_coarse_sub_pc_factor_shift_type NONZERO
-option_left -ksp_view <br>
</font></div>
</blockquote>
<div><br>
</div>
<div style="">This is what debugging is about. We are not
running your problem. How could this be debugged?</div>
<div style=""><br>
</div>
<div style="">1) Run the problem w/o a null space so that it
finishes</div>
<div style=""><br>
</div>
<div style="">2) Look at the output for -ksp_view</div>
<div style=""><br>
</div>
<div style="">3) Does the coarse solver say that it is
shifted?</div>
<div style=""><br>
</div>
<div style="">4) Are there options which were unused?</div>
<div style=""><br>
</div>
<div style=""> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF"><font face="Ubuntu">
still produces the same error:<br>
<br>
[0]PCSetData_AGG bs=1 MM=131072<br>
[0]PETSC ERROR: --------------------- Error Message
------------------------------------<br>
[0]PETSC ERROR: Detected zero pivot in LU
factorization:<br>
see <a moz-do-not-send="true"
href="http://www.mcs.anl.gov/petsc/documentation/faq.html#ZeroPivot"
target="_blank">http://www.mcs.anl.gov/petsc/documentation/faq.html#ZeroPivot</a>!<br>
[0]PETSC ERROR: Zero pivot row 280 value 6.56964e-17
tolerance 2.22045e-14!<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: Petsc Release Version 3.3.0, Patch 3,
Wed Aug 29 11:26:24 CDT 2012<br>
[0]PETSC ERROR: See docs/changes/index.html for recent
updates.<br>
[0]PETSC ERROR: See docs/faq.html for hints about
trouble shooting.<br>
[0]PETSC ERROR: See docs/index.html for manual pages.<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: ./hit on a named nid15363 by Unknown
Fri May 24 17:06:50 2013<br>
[0]PETSC ERROR: Libraries linked from<br>
[0]PETSC ERROR: Configure run at<br>
[0]PETSC ERROR: Configure options<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: MatPivotCheck_none() line 583 in
src/mat/impls/aij/seq//ptmp/skelly/petsc/3.3.03/cray_interlagos_build/real/src/include/petsc-private/matimpl.h<br>
[0]PETSC ERROR: MatPivotCheck() line 602 in
src/mat/impls/aij/seq//ptmp/skelly/petsc/3.3.03/cray_interlagos_build/real/src/include/petsc-private/matimpl.h<br>
[0]PETSC ERROR: MatLUFactorNumeric_SeqAIJ() line 585
in src/mat/impls/aij/seq/aijfact.c<br>
[0]PETSC ERROR: MatLUFactorNumeric() line 2803 in
src/mat/interface/matrix.c<br>
[0]PETSC ERROR: PCSetUp_LU() line 160 in
src/ksp/pc/impls/factor/lu/lu.c<br>
[0]PETSC ERROR: PCSetUp() line 832 in
src/ksp/pc/interface/precon.c<br>
[0]PETSC ERROR: KSPSetUp() line 278 in
src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: PCSetUpOnBlocks_BJacobi_Singleblock()
line 715 in src/ksp/pc/impls/bjacobi/bjacobi.c<br>
[0]PETSC ERROR: PCSetUpOnBlocks() line 865 in
src/ksp/pc/interface/precon.c<br>
[0]PETSC ERROR: KSPSetUpOnBlocks() line 154 in
src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: KSPSolve() line 403 in
src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: PCSetUpOnBlocks_BJacobi_Singleblock()
line 715 in src/ksp/pc/impls/bjacobi/bjacobi.c<br>
[0]PETSC ERROR: PCSetUpOnBlocks() line 865 in
src/ksp/pc/interface/precon.c<br>
[0]PETSC ERROR: KSPSetUpOnBlocks() line 154 in
src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: KSPSolve() line 403 in
src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: PCMGMCycle_Private() line 20 in
src/ksp/pc/impls/mg/mg.c<br>
[0]PETSC ERROR: PCMGMCycle_Private() line 49 in
src/ksp/pc/impls/mg/mg.c<br>
[0]PETSC ERROR: PCMGMCycle_Private() line 49 in
src/ksp/pc/impls/mg/mg.c<br>
[0]PETSC ERROR: PCMGMCycle_Private() line 49 in
src/ksp/pc/impls/mg/mg.c<br>
[0]PETSC ERROR: PCApply_MG() line 326 in
src/ksp/pc/impls/mg/mg.c<br>
[0]PETSC ERROR: PCApply() line 384 in
src/ksp/pc/interface/precon.c<br>
[0]PETSC ERROR: KSPSolve_CG() line 139 in
src/ksp/ksp/impls/cg/cg.c<br>
[0]PETSC ERROR: KSPSolve() line 446 in
src/ksp/ksp/interface/itfunc.c<br>
<br>
</font>
<div>On 05/24/2013 02:51 PM, Jed Brown wrote:<br>
</div>
<blockquote type="cite">
<pre>Michele Rosso <a moz-do-not-send="true" href="mailto:mrosso@uci.edu" target="_blank"><mrosso@uci.edu></a> writes:
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre> With petsc-3.4 (which you should upgrade to), use
-mg_coarse_sub_pc_factor_shift_type NONZERO
</pre>
</blockquote>
</blockquote>
<pre>Actually, use this with petsc-3.3 also (and please upgrade to
petsc-3.4).
The option you were passing was not being used.
</pre>
</blockquote>
<br>
</div>
</blockquote>
</div>
<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
</div>
</div>
</blockquote>
<br>
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