[petsc-users] unexpected behavior of the snes solver

[Matthew Knepley]

On Mon, Apr 23, 2012 at 9:23 AM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> Hi,
>
> I am implementing both FormFunction and FormJacobian for the SNES
> solver. It seems to start off correctly, with the 2 functions being
> called one after another in a loop, and with ||Ax-b|| decreasing about
> 3 orders of magnitude. But then only the FormFunction is being called
> several times, without subsequent calls to FormJacobian and obviously
> the residue is not being reduced any further, because there are no
> calls to the underlying ksp. If I inspect the solution it looks
>

This is a line search. If you upgrade to petsc-dev, line search has a lot
more diagnostics.

   Matt


> qualitatively "on the way" to the expected one, but the values are not
> correct, just as if the iterations were prematurely stopped. What sort
> of a problem can such a behavior indicate?
>
> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120423/c6772a59/attachment-0001.htm>