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Hello all,<br>
I did some other tests. Now, it is narrow down to this
situation:<br>
The domain and grid size is: 163*81*41 with 0.0125 = dx=dy=dz.
The boundary condition is still the same. <br>
The code runs well with 4 processes while the same problem
occurs when I was trying to use more than 4 processes (e.g. 6 or 8
processes). <br>
<br>
Hope this helps to detect the problem. <br>
<br>
thanks,<br>
Alan<br>
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-------- Original Message --------
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<th nowrap="nowrap" valign="BASELINE" align="RIGHT">Subject:
</th>
<td>A quick question on 'un-symmetric graph'</td>
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<th nowrap="nowrap" valign="BASELINE" align="RIGHT">Date: </th>
<td>Wed, 02 Jan 2013 15:41:47 -0600</td>
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<th nowrap="nowrap" valign="BASELINE" align="RIGHT">From: </th>
<td>Zhenglun (Alan) Wei <a class="moz-txt-link-rfc2396E" href="mailto:zhenglun.wei@gmail.com"><zhenglun.wei@gmail.com></a></td>
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<th nowrap="nowrap" valign="BASELINE" align="RIGHT">To: </th>
<td>PETSc users list <a class="moz-txt-link-rfc2396E" href="mailto:petsc-users@mcs.anl.gov"><petsc-users@mcs.anl.gov></a></td>
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<pre>Dear folks,
Here I came across a problem.
[0]PETSC ERROR: Petsc has generated inconsistent data!
[0]PETSC ERROR: Have un-symmetric graph (apparently). Use
'-pc_gamg_sym_graph true' to symetrize the graph or '-pc_gamg_threshold
0.0' if the matrix is structurally symmetric.!
My code basically uses PETSc /src/ksp/ksp/example/tutorial/ex45.c
to solve the Poisson equation with the Dirichlet BC in x-direction and
the Periodic BC in y- and z- direction.
The executable file is:
mpiexec -f $PBS_NODEFILE -np 32 ./ex45 -pc_type gamg -ksp_type cg
-pc_gamg_agg_nsmooths 1 -mg_levels_ksp_max_it 1 -mg_levels_ksp_type
richardson -ksp_rtol 1.0e-7
There is no problem for my code when I use small computational
domain (83*41*21 with single core and even 163*81*41 with 4 processes).
However, when I increase the domain size (323*161*81 with 32 processes),
the error comes up. I wonder what's the possible reason of this kind of
problem. Do you need any of my output in order to do some further
inspection? or I just need to blindly add '-pc_gamg_sym_graph true' in
PETSc option?
thanks,
Alan
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