[petsc-users] about linear solver convergence

[behzad baghapour]

I found that I should set up KSP in each Newton iteration ( if I don't want
to use SNES I think!).
Then KSP linear solver converged and my problem is solved.
By the way, Is it correct to re-setup KSP in each Newton iteration or I can
use a better way?


On Tue, Oct 11, 2011 at 7:45 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Tue, Oct 11, 2011 at 11:13 AM, behzad baghapour <
> behzad.baghapour at gmail.com> wrote:
>
>> Okey. I checked the condition number "max/min".
>> It increases significantly in each ksp iterations!!!
>>
>
> The approximation is becoming better. The condition number is harder to
> actually compute than the solution.
>
> Bottom line: You have a hard problem. Iterative methods do not work on hard
> problems without specialized
> preconditioners. I recommend a literature search on solvers for your
> equations.
>
>    Matt
>
>
>> Is it correct when the Jacobian matrix is fixed for each ksp iterations or
>> it is due to my fault?
>>
>> On Tue, Oct 11, 2011 at 7:28 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>
>>> On Tue, Oct 11, 2011 at 10:55, behzad baghapour <
>>> behzad.baghapour at gmail.com> wrote:
>>>
>>>> OK. Then how I can calculate and monitor the "condition number" in ksp?
>>>
>>>
>>> -ksp_monitor_singular_value
>>>
>>
>>
>>
>> --
>> ==================================
>> Behzad Baghapour
>> Ph.D. Candidate, Mechecanical Engineering
>> University of Tehran, Tehran, Iran
>> https://sites.google.com/site/behzadbaghapour
>> Fax: 0098-21-88020741
>> ==================================
>>
>>
>
>
> --
> 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
>



-- 
==================================
Behzad Baghapour
Ph.D. Candidate, Mechecanical Engineering
University of Tehran, Tehran, Iran
https://sites.google.com/site/behzadbaghapour
Fax: 0098-21-88020741
==================================
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