[petsc-users] Convergence trouble with SNES and CG
Matthew Knepley
knepley at gmail.com
Mon Feb 22 18:10:43 CST 2016
On Mon, Feb 22, 2016 at 6:02 PM, David Knezevic <david.knezevic at akselos.com>
wrote:
> On Mon, Feb 22, 2016 at 6:57 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>> Add -ksp_converged_reason
>>
>
>
> That gives "DIVERGED_INDEFINITE_PC". The full output is below:
>
Just for testing, replace CG with GMRES.
Thanks,
Matt
>
> 105 KSP Residual norm 7.099534889984e-05
> 106 KSP Residual norm 6.615351528474e-05
> 107 KSP Residual norm 6.303646443688e-05
> Linear solve converged due to CONVERGED_RTOL iterations 107
> NL step 5, |residual|_2 = 1.996487e+01
> 0 KSP Residual norm 5.844456247091e+00
> 1 KSP Residual norm 1.308756943973e+00
> 2 KSP Residual norm 7.545133187463e-01
> 3 KSP Residual norm 1.346068942607e+00
> Linear solve did not converge due to DIVERGED_INDEFINITE_PC iterations 4
> SNES Object: 1 MPI processes
> type: newtonls
> maximum iterations=50, maximum function evaluations=10000
> tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
> total number of linear solver iterations=535
> total number of function evaluations=11
> norm schedule ALWAYS
> SNESLineSearch Object: 1 MPI processes
> type: bt
> interpolation: cubic
> alpha=1.000000e-04
> maxstep=1.000000e+08, minlambda=1.000000e-12
> tolerances: relative=1.000000e-08, absolute=1.000000e-15,
> lambda=1.000000e-08
> maximum iterations=40
> KSP Object: 1 MPI processes
> type: cg
> maximum iterations=10000, initial guess is zero
> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
> left preconditioning
> using NATURAL norm type for convergence test
> PC Object: 1 MPI processes
> type: ilu
> ILU: out-of-place factorization
> 0 levels of fill
> tolerance for zero pivot 2.22045e-14
> matrix ordering: natural
> factor fill ratio given 1, needed 1
> Factored matrix follows:
> Mat Object: 1 MPI processes
> type: seqaij
> rows=967608, cols=967608
> package used to perform factorization: petsc
> total: nonzeros=7.55539e+07, allocated nonzeros=7.55539e+07
> total number of mallocs used during MatSetValues calls =0
> using I-node routines: found 322536 nodes, limit used is 5
> linear system matrix = precond matrix:
> Mat Object: () 1 MPI processes
> type: seqaij
> rows=967608, cols=967608
> total: nonzeros=7.55539e+07, allocated nonzeros=7.55539e+07
> total number of mallocs used during MatSetValues calls =0
> using I-node routines: found 322536 nodes, limit used is 5
> Number of nonlinear iterations: 5
> Nonlinear solver convergence/divergence reason: DIVERGED_LINEAR_SOLVE
>
>
>
>
--
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
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