[petsc-users] Snes behavior
Ryan Yan
vyan2000 at gmail.com
Sun Jan 10 15:52:33 CST 2010
Hi Barry,
Yes, exactly. The original multi-components system scale quite unevenly. I
will try to rescale it.
Could this be helpful to show some promise on quadratic convergence?
Thanks a lot,
Yan
On Sun, Jan 10, 2010 at 4:35 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> You already got a 10^16 drop in the residual norm. It is not realistic to
> expect to get much more than that for double precision calculations. Perhaps
> your original F() has some funky scaling of different components that you
> can fix.
>
>
>
> Barry
>
>
> On Jan 10, 2010, at 2:55 PM, Ryan Yan wrote:
>
> Hi All,
>> I am solving a nonlinear system using snes. The -snes_monitor option has
>> the following output:
>>
>> 0 SNES Function norm 2.640163923729e+09
>> 1 SNES Function norm 1.047643565314e+08
>> 2 SNES Function norm 1.712732074788e+06
>> 3 SNES Function norm 1.002169173269e+04
>> 4 SNES Function norm 1.655878303433e+03
>> 5 SNES Function norm 3.746498305706e+02
>> 6 SNES Function norm 8.317435704773e+01
>> 7 SNES Function norm 1.857639969641e+01
>> 8 SNES Function norm 4.149691057773e+00
>> 9 SNES Function norm 9.265604042412e-01
>> 10 SNES Function norm 2.069527103214e-01
>> 11 SNES Function norm 4.624186491082e-02
>> 12 SNES Function norm 1.035558432688e-02
>> 13 SNES Function norm 2.341362958811e-03
>> 14 SNES Function norm 5.507445427277e-04
>> 15 SNES Function norm 1.485123568354e-04
>> 16 SNES Function norm 5.180043781814e-05
>> 17 SNES Function norm 2.341966514486e-05
>> 18 SNES Function norm 1.344936158651e-05
>> 19 SNES Function norm 1.054812641176e-05
>> Number of Newton iterations = 19
>> Converged reason is 4
>>
>> It looks like the iterate never falls into a quadratic convergence region
>> before it converges. Is there any hint to understand this behavior?
>>
>> Thanks a lot,
>>
>> Yan
>>
>>
>>
>
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