[petsc-users] ex12 poisson solver

[Matthew Knepley]

On Tue, Oct 10, 2017 at 5:09 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Oct 9, 2017, at 6:56 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.
>
>    Pretty bad default. Maybe better to have P1 be the default.
>

I will look into it. I recall something being hard about setting everything
up. It would be nice to have
a better system for default values for options database keys.

  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/
>
>


-- 
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20171010/478f9285/attachment.html>