[petsc-users] about linear solver convergence

[Matthew Knepley]

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
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