[petsc-dev] snes_type test

[Mark Adams]

Does this look good:

Norm of matrix ratio 2.19793e-09, difference 2.14739e-07 (user-defined
state)
Norm of matrix ratio 1.10356e-08, difference 1.07917e-06 (constant state
-1.0)
Norm of matrix ratio 1.15084e-08, difference 1.12541e-06 (constant state
1.0)


On Thu, Aug 17, 2017 at 12:44 AM, Mark Adams <mfadams at lbl.gov> wrote:

> I see, I had a tiny time step that make the Jacobian big and the errors
> small.
>
> On Thu, Aug 17, 2017 at 12:30 AM, Mark Adams <mfadams at lbl.gov> wrote:
>
>>
>>
>> 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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