On Sat, Nov 5, 2011 at 1:23 PM, Dominik Szczerba <span dir="ltr"><<a href="mailto:dominik@itis.ethz.ch">dominik@itis.ethz.ch</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
I am a newcomer to Petsc non-linear capabilities, so far implementing<br>
such things myself, only delegating linear solves to Petsc.<br>
<br>
I want to start small by porting a very simple code using fixed point<br>
iterations as follows: A(x)x = b(x) is approximated as A(x0)x = b(x0),<br>
then solved by KSP for x, then x0 is updated to x, then repeat until<br>
convergence.<br>
<br>
In the documentation chapter 5 I see all sorts of sophisticated Newton<br>
type methods, requiring computation of the Jacobian. Is the above<br>
defined simple method still accessible somehow in Petsc or such<br>
triviality can only be done by hand? Which one from the existing<br>
nonlinear solvers would be a closest match both in simplicity and<br>
robustness (even if slow performance)?<br></blockquote><div><br></div><div>You want -snes_type nrichardson. All you need is to define the residual.</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Regards,<br>
<font color="#888888">Dominik<br>
</font></blockquote></div><br><br clear="all"><div><br></div>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>