[petsc-users] confused by the converged reason output

[Michael Wick]

Yes, it returns:

Linear m_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 3



On Fri, Jul 19, 2019 at 9:20 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Fri, Jul 19, 2019 at 11:14 AM Michael Wick via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
>
>> Hi PETSc team:
>>
>> I am a bit confused by the output of converged reason. I set the relative
>> tolerance to be 10^{-3}. In my run, I get the monitor true residual to be
>> as follows.
>>
>
> Can you run with -ksp_converged_reason?
>
>   Thanks,
>
>      Matt
>
>
>> 0 KSP preconditioned resid norm 5.402205955230e-11 true resid norm
>> 9.999870838355e-01 ||r(i)||/||b|| 1.000000000000e+00
>>     1 KSP preconditioned resid norm 2.240069771831e-12 true resid norm
>> 2.329743436488e-01 ||r(i)||/||b|| 2.329773528226e-01
>>     2 KSP preconditioned resid norm 3.394412665922e-13 true resid norm
>> 7.296473323081e-02 ||r(i)||/||b|| 7.296567566748e-02
>>     3 KSP preconditioned resid norm 4.936386334724e-14 true resid norm
>> 1.313944571812e-02 ||r(i)||/||b|| 1.313961543155e-02
>>
>> And the converged reason is solve converged due to CONVERGED_RTOL
>> iterations 3. The relative error is quite far from the prescribed
>> tolerance. Is there something I should know about the stopping criteria?
>>
>> The ks_view output is
>> Linear m_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 3
>> KSP Object:(m_fieldsplit_0_) 24 MPI processes
>>   type: gmres
>>     GMRES: restart=100, using Classical (unmodified) Gram-Schmidt
>> Orthogonalization with no iterative refinement
>>     GMRES: happy breakdown tolerance 1e-30
>>   maximum iterations=100, initial guess is zero
>>   tolerances:  relative=0.001, absolute=1e-50, divergence=10000
>>   left preconditioning
>>   using PRECONDITIONED norm type for convergence test
>> PC Object:(m_fieldsplit_0_) 24 MPI processes
>>   type: hypre
>>     HYPRE BoomerAMG preconditioning
>>     HYPRE BoomerAMG: Cycle type V
>>     HYPRE BoomerAMG: Maximum number of levels 25
>>     HYPRE BoomerAMG: Maximum number of iterations PER hypre call 1
>>     HYPRE BoomerAMG: Convergence tolerance PER hypre call 0
>>     HYPRE BoomerAMG: Threshold for strong coupling 0.25
>>     HYPRE BoomerAMG: Interpolation truncation factor 0
>>     HYPRE BoomerAMG: Interpolation: max elements per row 0
>>     HYPRE BoomerAMG: Number of levels of aggressive coarsening 0
>>     HYPRE BoomerAMG: Number of paths for aggressive coarsening 1
>>     HYPRE BoomerAMG: Maximum row sums 0.9
>>     HYPRE BoomerAMG: Sweeps down         1
>>     HYPRE BoomerAMG: Sweeps up           1
>>     HYPRE BoomerAMG: Sweeps on coarse    1
>>     HYPRE BoomerAMG: Relax down          symmetric-SOR/Jacobi
>>     HYPRE BoomerAMG: Relax up            symmetric-SOR/Jacobi
>>     HYPRE BoomerAMG: Relax on coarse     Gaussian-elimination
>>     HYPRE BoomerAMG: Relax weight  (all)      1
>>     HYPRE BoomerAMG: Outer relax weight (all) 1
>>     HYPRE BoomerAMG: Using CF-relaxation
>>     HYPRE BoomerAMG: Measure type        local
>>     HYPRE BoomerAMG: Coarsen type        HMIS
>>     HYPRE BoomerAMG: Interpolation type  ext+i
>>   linear system matrix = precond matrix:
>>   Mat Object:  (m_fieldsplit_0_)   24 MPI processes
>>     type: mpiaij
>>     rows=115812, cols=115812
>>     total: nonzeros=1.34986e+06, allocated nonzeros=1.34986e+06
>>     total number of mallocs used during MatSetValues calls =0
>>       not using I-node (on process 0) routines
>>
>>
>> Thanks,
>>
>> Mike
>>
>>
>>
>
> --
> 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.cse.buffalo.edu/~knepley/>
>
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