[petsc-users] infinite loop with NEWTONTR?

[Barry Smith]

  It will take a very long time

On Apr 28, 2014, at 9:14 AM, Norihiro Watanabe <norihiro.w at gmail.com> wrote:

> I cannot surely say my Jacobian for this particular problem is correct, as I have not checked it. For a smaller problem, I've already checked its correctness using -snes_type test or -snes_compare_explicit (but linear solve and nonlinear solve with FD one need a few more iterations than with my Jacobian). To make it sure, now I started -snes_type test for the problem and will update you once it finished. By the way, I'm waiting the calculation for more than three hours now. Is it usual for a large problem (>1e6 dof) or is there something wrong? 
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> On Mon, Apr 28, 2014 at 6:34 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
>   I have run your code. I changed to use -snes_type newtonls and also -snes_mf_operator  there is something wrong with your Jacobian:
> 
>   Without -snes_mf_operator
>  0 SNES Function norm 1.821611413735e+03
>     0 KSP Residual norm 1821.61
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     1 KSP Residual norm 0.000167024
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     2 KSP Residual norm 7.66595e-06
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     3 KSP Residual norm 4.4581e-07
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     4 KSP Residual norm 3.77537e-08
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     5 KSP Residual norm 2.20453e-09
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     6 KSP Residual norm 1.711e-10
>   Linear solve converged due to CONVERGED_RTOL iterations 6
> 
> with -snes_mf_operator
> 
>   0 SNES Function norm 1.821611413735e+03
>     0 KSP Residual norm 1821.61
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     1 KSP Residual norm 1796.39
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     2 KSP Residual norm 1786.2
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     3 KSP Residual norm 1741.11
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     4 KSP Residual norm 1733.92
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     5 KSP Residual norm 1726.57
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     6 KSP Residual norm 1725.35
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     7 KSP Residual norm 1723.89
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     8 KSP Residual norm 1715.41
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>     9 KSP Residual norm 1713.72
>     Linear solve converged due to CONVERGED_ITS iterations 1
>     Linear solve converged due to CONVERGED_RTOL iterations 1
>    10 KSP Residual norm 1702.84
>     Linear solve converged due to CONVERGED_ITS iterations 1
> 
> …
> 
>   This means your Jacobian is wrong. Your first order of business is to fix your Jacobian. I noticed in previous emails your discussion with Jed about switching to MatGetLocalSubMatrix() and using -snes_type test  YOU NEED TO DO THIS. You will get no where with an incorrect Jacobian. You need to fix your Jacobian before you do anything else! No amount of other options or methods will help you with a wrong Jacobian! Once you have a correct Jacobian if you still have convergence problems let us know and we can make further suggestions.
> 
>   Barry
> 
> On Apr 25, 2014, at 7:31 AM, Norihiro Watanabe <norihiro.w at gmail.com> wrote:
> 
> > Hi,
> >
> > In my simulation, nonlinear solve with the trust regtion method got stagnent after linear solve (see output below). Is it possible that the method goes to inifite loop? Is there any parameter to avoid this situation?
> >
> >   0 SNES Function norm 1.828728087153e+03
> >     0 KSP Residual norm 91.2735
> >     Linear solve converged due to CONVERGED_ITS iterations 1
> >     Linear solve converged due to CONVERGED_RTOL iterations 3
> >     1 KSP Residual norm 3.42223
> >   Linear solve converged due to CONVERGED_STEP_LENGTH iterations 1
> >
> >
> > Thank you in advance,
> > Nori
> 
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> 
> 
> -- 
> Norihiro Watanabe