[petsc-dev] snes_type test

[Mark Adams]

On Thu, Aug 17, 2017 at 12:22 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, Aug 16, 2017 at 10:14 AM, Mark Adams <mfadams at lbl.gov> wrote:
>
>> I just want to check the interpretation of snes_type test. Is this pretty
>> conclusively good?
>>
>
> It looks right, but the entires in the Jacobian are crazy. You should
> non-dimensionalize first.
>

This is non-dimensionalize and it is 2D FE 2nd order equation so everything
should be O(1), that is, there is no 1/h like term. And the domain is (1)
and the grid is small so h is O(1) anyway.


>
>   Matt
>
>
>> Testing hand-coded Jacobian, if the ratio is
>> O(1.e-8), the hand-coded Jacobian is probably correct.
>> Run with -snes_test_display to show difference
>> of hand-coded and finite difference Jacobian.
>> Norm of matrix ratio 1.38299e-16, difference 1.11738 (user-defined state)
>> Norm of matrix ratio 9.50529e-09, difference 7.67972e+07 (constant state
>> -1.0)
>> Norm of matrix ratio 1.07438e-08, difference 8.68036e+07 (constant state
>> 1.0)
>>
>>
>
>
> --
> 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
>
> http://www.caam.rice.edu/~mk51/
>
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