>> 1) What is 'func' on the SNESSetPicard manual page. It only says >> "function evaluation routine". What function? Do you mean Ax-b? >> 2) Is it supposed to perform better / more optimally then using >> FormFunction with FormJacobian and passing A as the Jacobian? > >
What is 'func' on the SNESSetPicard manual page. It only says "function evaluation routine". What function? Do you mean Ax-b? > All SNESSetPicard does is evaluate both A and b in "residual evaluation", > compute F(x) = A(x)x - b(x), and internally cache the matrix A(x). Using it > is completely optional. If you are willing to write residual evaluation for > the whole F(x), then you will benefit from having less expensive residual > evaluations, making line searches and matrix-free Newton (-snes_mf_operator) > affordable. I understood from the documentation sec. 5.1 and 5.6 that -snes_mf_operator is not well suited for unstructured problems, rather for structured problems with known stencil. Is it not so? Dominik
