<div class="gmail_quote">On Sat, Sep 15, 2012 at 2:16 AM, TAY wee-beng <span dir="ltr"><<a 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">
<div bgcolor="#FFFFFF" text="#000000">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></div></blockquote><div><br></div><div>Is it symmetric? Since you are using petsc-dev, you should pull the latest. Then if the error below persists, run in a debugger with -fp_trap to find what causes the floating point exception.</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
<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 href="http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind" target="_blank">http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind</a>[0]PETSC
ERROR: or try <a href="http://valgrind.org" target="_blank">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?</div></blockquote></div><br>