[petsc-users] clarification of SNES / FormFunction

[Dominik Szczerba]

> Newton-based SNES solves for snes->vec_sol_update, but evaluates at
> snes->vec_sol and using another vector inside the line search.
>
> If you are writing code that depends on the Vec being the same, you're doing
> it wrong.

I am currently assuming they are different and am using the "x" from
the signature to set up my A(x) and b(x). I was thinking if they are
the same (i.e. corresponding to x_n in the Newton method), I could
significantly simplify my code. But apparently "x" in the signature is
not simply x_n because of the involved line search, correct me if I am
wrong.

Thanks,
Dominik