[petsc-users] Snes failled with reason -6

[Que Cat]

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?

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.

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
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