[petsc-users] some questions about snes

[Fande Kong]

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,
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