Line search question

[Ryan Yan]

Hi All,
I am trying to figure out how the line search is actually working in PETSc
and I am looking at this link,

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/SNES/SNESLineSearchGetParams.html

Can anyone help to explain why there is a J in the amijo condition?

*alpha *- The scalar such that .5*f_{n+1} . f_{n+1} <= .5*f_n . f_n - alpha
|f_n . J . f_n|


Considering the fact that the newton direction p_n provide a J^{-1} and the
gradient of the merit function( 1/2 f . f) provide a J, isn't correct to get
rid of J in the definition above?

Thanks for any suggestions,

Yan
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