[petsc-users] Snes failled with reason -6

[Que Cat]

Hi Matt,

Thanks for your response. The problem I tried to test has analytical
solution. I think something wrong with the matrix.




On Thu, Dec 19, 2013 at 4:54 PM, Matthew Knepley <knepley at gmail.com> wrote:

> 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/20131220/83cb9da4/attachment.html>