BOUNCE petsc-users at mcs.anl.gov: Non-member submission from [Marco Schauer <m.schauer at tu-bs.de>] (fwd)

[Matthew Knepley]

On Wed, May 28, 2008 at 8:12 AM, Satish Balay <balay at mcs.anl.gov> wrote:
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> Date: Wed, 28 May 2008 12:29:47 +0200
> From: Marco Schauer <m.schauer at tu-bs.de>
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> Subject: How to use SNES
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> Hello,
> I???d like to compute a nonlinear equation system. My system looks like
> this: K(u)*u=f, in which u, f are vectors and K is a Matrix that depends
> on u. I have already a function to calculate K, but I don???t now how can
> I use PETSc to solve this system?

The first thing to do is formulate the system as F(u) = 0, so that would be

  F(u) = K(u)*u - f

This is directly soluble with the option -snes_fd. If later you want
to provide the
Jacobian, you can.

  Matt

> Thanks for support, kind regard
> Marco Schauer
-- 
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