Special line search only for SNESNCG This line search uses the length "as if" the problem is linear (that is what is computed by the linear CG method) using the Jacobian of the function.
alpha = (r, r) / (p, Ap) = (f, f) / (y, Jy) where r (f) is the current residual (function value), p (y) is the current search direction.
Notes: This requires a Jacobian-vector product but does not require the solution of a linear system with the Jacobian
This is a "odd-ball" line search, we don't know if it is in the literature or used in practice by anyone.
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages