This is not the full FD Jacobian, but the one constructed by coloring. It's a hunch, but I'd bet DMComposite doesn't have a proper coloring in place. This should error out. I'll check out why not.
You don't have to alter the source to do this. You can use -snes_fd_coloring or -snes_fd. - Peter - Peter On Sep 29, 2013 3:07 PM, "Lulu Liu" <[email protected]> wrote: > Run the example /petsc/src/snes/examples/tutorials/ex28.c using the > following options(found in the makefile) > > ./ex28 -da_grid_x 20 -snes_converged_reason -snes_monitor_short > -problem_type 2 > > It works using default analytic Jacobian to solve coupled system, however, > I comment > > Line 434 : ierr = > SNESSetJacobian(snes,B,B,FormJacobian_All,user);CHKERRQ(ierr); > > and run the code again using the same options (i.e., FD Jacobian instead > of analytic Jacobian), we will get the results: > > Nonlinear solve did not converge due to DIVERGED_MAX_IT iterations 50 > > Could you explain why it does not work using FD Jacobian in this example? > > Thanks > > > > ------------------------------ > This message and its contents, including attachments are intended solely > for the original recipient. If you are not the intended recipient or have > received this message in error, please notify me immediately and delete > this message from your computer system. Any unauthorized use or > distribution is prohibited. Please consider the environment before printing > this email.
