[petsc-users] confused by the converged reason output

[Michael Wick]

Hi Matt:

At the third iteration, the relative error is 1.313961543155e-02. Am I
looking at the correct place?

Thanks,

M

On Fri, Jul 19, 2019 at 11:47 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Fri, Jul 19, 2019 at 11:21 AM Michael Wick <michael.wick.1980 at gmail.com>
> wrote:
>
>> Yes, it returns:
>>
>> Linear m_fieldsplit_0_ solve converged due to CONVERGED_RTOL iterations 3
>>
>
> 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
>
> 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
>
> Note that the relative tolerance is 0.001, so the termination seems
> correct.
>
>    Thanks,
>
>     Matt
>
>
>> 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/>
>>>
>>
>
> --
> 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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