[petsc-users] unexpected behavior of the snes solver

[Jed Brown]

The linear solve computed a search direction that was not a descent
direction. It determined this by attempting a line search.
On Apr 23, 2012 8:23 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
> 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
>
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