[petsc-users] conditioning of snes with dmcomposite & grid sequencing

[Matthew Knepley]

On Fri, Sep 11, 2015 at 1:05 PM, Gideon Simpson <gideon.simpson at gmail.com>
wrote:

> Since the problem has not only the two components in the DM, but the
> second component has 4 degrees of freedom per mesh point, I thought it best
> to do the post processing separately.  See attached
>

So the whole thing is being controlled by 1 variable.

We should try freezing everything else, and just solving that scalar
equation I guess.

   Matt


> -gideon
>
> On Sep 11, 2015, at 10:16 AM, Matthew Knepley <knepley at gmail.com> wrote:
>
> On Fri, Sep 11, 2015 at 9:08 AM, Gideon Simpson <gideon.simpson at gmail.com>
>  wrote:
>
>> Following up on the previous thread, for my dm composite problem, I find
>> that at the end of the first grid sequence,where it fails to converge, the
>> distribution of the norms between the two pieces are:
>>
>>  39 SNES Function norm 2.253098577796e+02
>>  40 SNES Function norm 2.253098577331e+02
>>  41 SNES Function norm 2.253098577228e+02
>>  42 SNES Function norm 2.253098577212e+02
>>  43 SNES Function norm 2.253098577174e+02
>>  44 SNES Function norm 2.253098577166e+02
>>  45 SNES Function norm 2.253098577158e+02
>>  46 SNES Function norm 2.253098577157e+02
>>  47 SNES Function norm 2.253098577156e+02
>>  48 SNES Function norm 2.253098577156e+02
>> Nonlinear solve did not converge due to DIVERGED_LINE_SEARCH iterations 48
>>  ||r|| = 225.31, 7999 entries
>>  ||rp|| = 140.021, 3 entries
>>  ||rQ|| = 176.518, 7996 entries
>>
>> Since I think we were convinced that this was intrinsic to the problem,
>> and not a function of the Jacobian function, I am using my Jacobian.
>>
>
> Okay, I see no pattern in the fields. Lets plot these 2 vectors, -vec_view
> draw, and screenshot.
>
>   Matt
>
>
>> -gideon
>>
>
>
>
> --
> 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
>
>
>


-- 
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
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