[petsc-users] about linear solver convergence

[behzad baghapour]

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
==================================
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