[petsc-dev] KSP rtol

[Matthew Knepley]

On Wed, Dec 14, 2011 at 12:45 PM, Mark F. Adams <mark.adams at columbia.edu>wrote:

> I have a nonlinear problem and am finding the the convergence test for the
> interior PETSc linear solver is apparently testing against the norm of the
> first linear solve (see appended).  This is clearly not what anyone would
> want, is this the intended semantics?  Is there perhaps a method to reset
> rtol?
>

-snes_view -ksp_view?

  Matt


> Mark
>
> Picard iteration 0 max(resid) = 781020
>  0 KSP Residual norm 2.499264167662e+07
>  1 KSP Residual norm 6.330915810095e+06
>  2 KSP Residual norm 1.856999435466e+06
>  3 KSP Residual norm 3.967325725053e+05
>  4 KSP Residual norm 9.037332775808e+04
>  5 KSP Residual norm 1.826960320400e+04
> Linear solve converged due to CONVERGED_RTOL iterations 5
> Picard iteration 1 max(resid) = 727577 ------- Rate = 1.07345
>  0 KSP Residual norm 6.885328126772e+06
>  1 KSP Residual norm 2.150319244570e+06
>  2 KSP Residual norm 2.297759417371e+05
>  3 KSP Residual norm 3.321819214451e+04
>  4 KSP Residual norm 4.155970071625e+03
> Linear solve converged due to CONVERGED_RTOL iterations 4
> Picard iteration 2 max(resid) = 486788 ------- Rate = 1.49465
>  0 KSP Residual norm 2.987417661953e+06
>  1 KSP Residual norm 5.046119985008e+05
>  2 KSP Residual norm 3.882757664605e+04
>  3 KSP Residual norm 4.106091678345e+03
> Linear solve converged due to CONVERGED_RTOL iterations 3
> Picard iteration 3 max(resid) = 137348 ------- Rate = 3.54418
>  0 KSP Residual norm 7.285359985607e+05
>  1 KSP Residual norm 9.132700545850e+04
>  2 KSP Residual norm 6.834608381922e+03
> Linear solve converged due to CONVERGED_RTOL iterations 2
> Picard iteration 4 max(resid) = 25082.7 ------- Rate = 5.47582
>  0 KSP Residual norm 1.207523847817e+05
>  1 KSP Residual norm 1.286174706329e+04
> Linear solve converged due to CONVERGED_RTOL iterations 1
> Picard iteration 5 max(resid) = 5723.21 ------- Rate = 4.38264
>  0 KSP Residual norm 2.211945822133e+04
> Linear solve converged due to CONVERGED_RTOL iterations 0
>
>


-- 
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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