[petsc-users] about linear solver convergence

[behzad baghapour]

What is the difference between "unpreconditioned resid norm" and "true resid
norm" in -ksp_monitor?

On Tue, Oct 11, 2011 at 6:50 PM, behzad baghapour <
behzad.baghapour at gmail.com> wrote:

> Thanks, I monitored the ksp but I found that " unpreconditioned resid norm"
> and "true resid norm" are exactly the same. I can't understand while I set
> Jacobian = Precondition matrix ?!!!
>
> In addition, I am solving true Newton iterations and I saw that first
> iteration is good (as I got from previous linear solvers) and the norm of
> the matrix is what I expected BUT for the next nonlinear iteration, the
> linear iterations can not converge to desired tolerance!!!
>
>
>
> On Tue, Oct 11, 2011 at 6:18 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>> http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#kspdiverged
>>
>>
>> On Oct 11, 2011, at 9:45 AM, behzad baghapour wrote:
>>
>> > Dear all,
>> >
>> > I set my Jacobian matrix in petsc and test it to ensure for correctness
>> for Jacobian and RHS function. ( also precondition = jacobian )
>> > I have solved my problem before with some other solvers (gmers/ILU(2))
>> and the convergence has been achieved within 15 - 16 iterations.
>> >
>> > But in petsc the linear solver (ksp=GMRES) is not converged within this
>> number ( or may be converged in more than 700 iterations!!! ). I know that I
>> should have a mistake but I can't predict it?
>> >
>> > Please help me what parts of petsc solver I should check?
>> >
>> > Regards,
>> > Behzad
>> >
>> > --
>> > ==================================
>> > Behzad Baghapour
>> > Ph.D. Candidate, Mechecanical Engineering
>> > University of Tehran, Tehran, Iran
>> > https://sites.google.com/site/behzadbaghapour
>> > Fax: 0098-21-88020741
>> > ==================================
>> >
>>
>>
>
>
> --
> ==================================
> Behzad Baghapour
> Ph.D. Candidate, Mechecanical Engineering
> University of Tehran, Tehran, Iran
> https://sites.google.com/site/behzadbaghapour
> Fax: 0098-21-88020741
> ==================================
>
>


-- 
==================================
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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