[petsc-users] confused by the converged reason output

[Matthew Knepley]

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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