Dear all, I have a question on the PETSc option '-snes_mf_operator'. I am reading the <PETSc Users Manual Revision 3.3>. On page 100, 2nd paragraph, it says:
============================================================================== "However, it allows us to check the analytic Jacobian we construct in FormJacobian() by passing the -snes_mf_operator flag. This causes PETSc to approximate the Jacobian using finite differencing of the function evaluation (discussed in section 5.6), and the analytic Jacobian becomes merely the preconditioner." ============================================================================== I wonder, if the '-snes_mf_operator' option is used, the Jacobian will always be calculated from the finite difference method while ignore whatever has been provided from user. One more question, if I pass '-snes' to PETSc, since it is direct Newton's method, I assume it will explicitly construct a Jacobian. Does this Jacobian come from user provided Jacobian or from the finite difference Jacobian? Thanks, Ling -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120927/b23d9336/attachment.html>