On Aug 27, 2011, at 12:52 PM, Milan Mitrovic wrote: > for the jacobian i use: > > call MatCreateShell(PETSC_COMM_WORLD, Np, Np, Ng, Ng, 0, Jac, info) > call MatShellSetOperation(Jac, MATOP_MULT, & > jacobian_multiplication, info) > > and do the multiplication myself because it is much faster. I tried > using parallel AIJ format but constructing the matrix took more than a > minute for my problem with only ~150 nonzero entries per row... (maybe > I was doing something very wrong) > > should I return to the AIJ version to see if the jacobian is correct?
If you have the code for both then add a simple switch in the code to allow changing back and forth very easily to debug things like Newton. For example with AIJ you can use a direct solver to eliminate most of the issues related to the linear solver from the problem of Newton's method. Barry
