On Mon, Aug 29, 2011 at 06:39, Milan Mitrovic <milan.v.mitrovic at gmail.com>wrote:
> so I guess this means that it is slightly wrong :) > Or your system is somewhat ill-conditioned. If you add '-mat_fd_type ds' to the last command line, are the errors similar or improve a bit? A different way to test for a correct Jacobian is to run with -snes_mf_operator -pc_type lu and check that it converges in 1 or occasionally 2 iterations. This also helps if the Jacobian is incorrect, but not visibly so on the first iteration (e.g. because nonlinearities are silent for the initial guess). > can you explain now what it is doing here (and why I get this > error)... > The error to exit early because "test" is not intended to actually solve the equation, -snes_type test is supposed to do that. > can I make it try to solve the equation with the > approximated fd jacobian (is it doing that already?) > -snes_mf_operator : solve with matrix-free finite differenced Jacobian, preconditioned using the matrix you assembled -snes_fd : assemble the dense FD operator (same as created by -snes_type test) and solve using that -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110829/62696564/attachment.htm>
