[petsc-users] ex12 poisson solver

[Matthew Knepley]

On Mon, Oct 9, 2017 at 12:56 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Oct 9, 2017 at 12:40 PM, Justin Chang <jychang48 at gmail.com> wrote:
>
>> You need this additional command line argument: -petscspace_order 1
>>
>
> Justin is correct. By default, it is P0, which would be a purely
> discontinuous solution to Laplace, without
> jump terms.
>

I would also note that all the tests are at the bottom of the file.

  Matt


>   Thanks,
>
>     Matt
>
>
>> On Mon, Oct 9, 2017 at 9:02 AM, David Fuentes <fuentesdt at gmail.com>
>> wrote:
>>
>>>
>>> Hi,
>>>
>>> I'm trying to use petsc 3.8.0 with ex12.c example to setup a poisson
>>> solver: http://www.mcs.anl.gov/petsc/petsc-current/src/snes/examples
>>> /tutorials/ex12.c.html
>>>
>>> I seem to be getting zeros in my jacobian with this example?
>>> I attached a debugger and the assembly routines seems ok... but am
>>> getting zero jacobian somewhere along the way to the MatAssembly...
>>> Am I missing something with the command line arguments ?
>>>
>>>
>>>
>>> $ ./ex12 -snes_type ksponly  -snes_monitor -snes_converged_reason
>>> -ksp_converged_reason -ksp_monitor -ksp_rtol 1.e-6 -pc_type jacobi -info
>>> -info_exclude null,pc,vec
>>> ------------------------------------------------------------
>>> --------------
>>> [[55310,1],0]: A high-performance Open MPI point-to-point messaging
>>> module
>>> was unable to find any relevant network interfaces:
>>>
>>> Module: OpenFabrics (openib)
>>>   Host: SCRGP2
>>>
>>> Another transport will be used instead, although this may result in
>>> lower performance.
>>> ------------------------------------------------------------
>>> --------------
>>> [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 8 X 8; storage space: 0
>>> unneeded,8 used
>>> [0] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0
>>> [0] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1
>>> [0] MatCheckCompressedRow(): Found the ratio (num_zerorows
>>> 0)/(num_localrows 8) < 0.6. Do not use CompressedRow routines.
>>> [0] MatSeqAIJCheckInode(): Found 8 nodes out of 8 rows. Not using Inode
>>> routines
>>> [0] DMGetDMSNES(): Creating new DMSNES
>>> [0] DMGetDMKSP(): Creating new DMKSP
>>>   0 SNES Function norm 1.414213562373e+00
>>> [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 8 X 8; storage space: 0
>>> unneeded,8 used
>>> [0] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0
>>> [0] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1
>>> [0] MatCheckCompressedRow(): Found the ratio (num_zerorows
>>> 0)/(num_localrows 8) < 0.6. Do not use CompressedRow routines.
>>> [0] SNESComputeJacobian(): Rebuilding preconditioner
>>>     0 KSP Residual norm 1.414213562373e+00
>>>     1 KSP Residual norm 1.414213562373e+00
>>> [0] KSPGMRESBuildSoln(): Likely your matrix or preconditioner is
>>> singular. HH(it,it) is identically zero; it = 0 GRS(it) = 1.41421
>>>   Linear solve did not converge due to DIVERGED_BREAKDOWN iterations 1
>>> [0] SNESSolve_KSPONLY(): iter=0, number linear solve failures 1 greater
>>> than current SNES allowed, stopping solve
>>> Nonlinear solve did not converge due to DIVERGED_LINEAR_SOLVE iterations
>>> 0
>>> Number of SNES iterations = 0
>>> L_2 Error: 0.751285
>>>
>>>
>>> configured with: ./config/configure.py --with-shared-libraries
>>> --with-clanguage=c++ --CFLAGS='-g -O0' --CXXFLAGS='-g -O0'
>>> --download-ctetgen  --download-triangle --with-debugging=yes
>>> --with-exodusii-lib=[/usr/lib/x86_64-linux-gnu/libexoIIv2.so]
>>> --with-netcdf-lib=[/usr/lib/libnetcdf.so] --with-netcdf-include=/usr/include
>>> --with-hdf5-include=/usr/include/hdf5/serial/
>>> --with-hdf5-lib=[/usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5.so]
>>> --with-c2html=0 --with-exodusii-include=/usr/include
>>>
>>>
>>> thanks!
>>> David
>>>
>>>
>>>
>>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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