[petsc-users] infinite loop with NEWTONTR?

Norihiro Watanabe norihiro.w at gmail.com
Tue Apr 29 09:19:41 CDT 2014 

Hi Barry,

Is it possible that -snes_mf_operator makes convergence of linear solves
slower if unknowns are poorly scaled for multiphysics problems? I gave up
to check Jacobian for the large problem because it takes too long time.
Instead I tested it with several different small size problems and noticed
scaling of my unknowns makes a difference in FD Jacobian. My unknowns are
two kinds: pressure (1e7) and temperature (1e3). I scaled pressure by 1e-5
and got the following different results from -snes_type test

without scaling
Norm of matrix ratio 3.81371e-05 difference 6.42349e+06 (user-defined state)

with scaling
Norm of matrix ratio 8.69182e-09 difference 1463.98 (user-defined state)

which may suggest that a differentiate parameter h is not properly set if
unknowns are poorly scaled. I also tested the scaling for the large problem
with keeping fluid properties constant and got the following different
convergence behaviours:

without -snes_mf_operator
  0 SNES Function norm 4.425457683773e+04
    0 KSP Residual norm 44254.6
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 2
    1 KSP Residual norm 0.000168321
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 2
    2 KSP Residual norm 8.18977e-06
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 2
    3 KSP Residual norm 4.75882e-07
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
    4 KSP Residual norm 4.06286e-08
  Linear solve converged due to CONVERGED_RTOL iterations 4
  1 SNES Function norm 2.229156139237e+05

with -snes_mf_operator
  0 SNES Function norm 4.425457683883e+04
    0 KSP Residual norm 44254.6
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 2
    1 KSP Residual norm 5255.66
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
    2 KSP Residual norm 1646.58
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
    3 KSP Residual norm 1518.05
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
...
   42 KSP Residual norm 0.656962
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
   43 KSP Residual norm 0.462202
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1

with -snes_mf_operator and scaling of pressure by 1e-5
  0 SNES Function norm 4.425457683773e+04
    0 KSP Residual norm 44254.6
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 2
    1 KSP Residual norm 1883.94
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
    2 KSP Residual norm 893.88
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
...
   42 KSP Residual norm 6.66081e-08
    Linear solve converged due to CONVERGED_ITS iterations 1
    Linear solve converged due to CONVERGED_RTOL iterations 1
   43 KSP Residual norm 2.17062e-08
  Linear solve converged due to CONVERGED_RTOL iterations 43
  1 SNES Function norm 2.200867439822e+05








On Mon, Apr 28, 2014 at 5:59 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   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?
> >
> >
> >
> >
> >
> > 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
> >
> >
> >
> >
> > --
> > Norihiro Watanabe
>
>


-- 
Norihiro Watanabe
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