[petsc-users] fixed point interations

[Matthew Knepley]

On Sat, Nov 5, 2011 at 1:23 PM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> I am a newcomer to Petsc non-linear capabilities, so far implementing
> such things myself, only delegating linear solves to Petsc.
>
> I want to start small by porting a very simple code using fixed point
> iterations as follows: A(x)x = b(x) is approximated as A(x0)x = b(x0),
> then solved by KSP for x, then x0 is updated to x, then repeat until
> convergence.
>
> In the documentation chapter 5 I see all sorts of sophisticated Newton
> type methods, requiring computation of the Jacobian. Is the above
> defined simple method still accessible somehow in Petsc or such
> triviality can only be done by hand? Which one from the existing
> nonlinear solvers would be a closest match both in simplicity and
> robustness (even if slow performance)?
>

You want -snes_type nrichardson. All you need is to define the residual.

   Matt


> Regards,
> Dominik
>



-- 
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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