[petsc-users] Linesearch algorithm

[Barry Smith]

On May 14, 2012, at 10:29 AM, behzad baghapour wrote:

> Dear Developers,
> 
> I wish to know when the algorithm of Linesearch used by SNESLineSearchCubic or SNESLineSearchQuadratic calls the Jacobian calculation routine defined by user? Is it a way to change the Jacobian before calling the line-search routines?
> 
> Thanks,
> BehZad

   The linesearch routines themselves never call a "compute Jacobian" routine. It is only SNESSolve_LS() that computes the Jacobian and then uses it in the linear solve.   Some of the line search routines reuse the previously computed Jacobian in a matrix vector product to determine the appropriate descent requirements. You can see the code in src/snes/impls/ls/ls.c

   Barry