Hi all, (1) The snes can solve my nonlinear problem with a default Jacobian provided in the Petsc using finite differences, but this method may cause some new nonzero allocations for the preallocated matrix.
(2) A Matrix-free version of snes also works well for my nonlinear problem, but it does not allow me to apply a preconditioner. What kind of algorithms are used for the matrix-free snes? Thanks, Fande,
