[petsc-users] Snes failled with reason -6

[Matthew Knepley]

On Thu, Dec 19, 2013 at 4:26 PM, Que Cat <quecat001 at gmail.com> wrote:

> Hello,
>
> I use SNES to solve the non linear coupled equations. I have checked the
> hand-coded jacobian with -snes_type test and received the result:
> Norm of matrix ratio 1.39606e-23 difference 1.53372e-14 (user-defined
> state)
> Norm of matrix ratio 3.03157e-10 difference 0.33305 (constant state -1.0)
> Norm of matrix ratio 3.03157e-10 difference 0.33305 (constant state 1.0)
> It said that "  if the ratio is O(1.e-8), the hand-coded Jacobian is
> probably correct." What is the second paramenter "difference 1.53372e-14
> ...."? Does it play any role in checking the accuracy of hand-coded
> jacobian?
>

It appears that your Jacobian is correct, or at least has an error that is
much smaller than most of the elements.


> The SNES solver for failed with the reason -6 "the line search failed". I
> tried with all other line search method stated in the PETSC manual, but
> they all failed.
>

Do you know that the problem has a solution. Its possible that there is no
real solution.

   Matt


> I tried to figure out what is wrong with my code? Could you please give me
> any recommendation to direct me how to check my code? I appreciate your
> help.
>
> QUe
>
>


-- 
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/20131219/1f816177/attachment.html>