[petsc-users] SNES and ghosted vector of unknowns

[Dominik Szczerba]

>> Thanks Barry for the hint.
>> I am indeed solving my nonlinear system using the Picard scheme.
>> I was once advised to set the Jacobian to my coefficient matrix "A" in
>> the FormJacobian function passed to SNES to achieve this goal (I am
>> still trying to get it to work with limited success though).
>> Are you suggesting I should abandon this approach in favor of the new
>> functionality in petsc-dev?
>
>  Yes if you want to do Picard then you should use SNESSetPicard() that is what it designed for.
>
>   Barry

Great to hear there is a dedicated functionality for the Picard
scheme. I have 2 related questions:

1) What is 'func' on the SNESSetPicard manual page. It only says
"function evaluation routine". What function? Do you mean Ax-b?
2) Is it supposed to perform better / more optimally then using
FormFunction with FormJacobian and passing A as the Jacobian?

Regards,
Dominik