Using the direct solver as a preconditioner I can't seem to find any difference between the results with -ksp_diagonal_scale vs the results without this option. I also cant tell if the diagonal scaling is actually being applied in this case.
Quoting Jed Brown <five9a2 at gmail.com>: > It just means that both matrix arguments A and B are the same. > > What happens if you use this direct solver as a preconditioner? > On May 17, 2012 2:23 PM, "Colin McAuliffe" <cjm2176 at columbia.edu> wrote: > >> Hello! >> >> I am solving a coupled multiphysics problem which has several different >> units, which leads to a poorly conditioned jacobian. I am using the >> following ksp options: >> >> -ksp_type preonly -pc_type lu -pc_factor_mat_solver_package umfpack >> >> The results I am getting are not right and I suspect that the conditioning >> of the jacobian may be playing a part in that. I would like to improve the >> conditioning by using -ksp_diagonal_scale, but adding it does not seem to >> help. The documentation for this option says 'this routine is only used if >> the matrix and preconditioner matrix are the same thing'. >> >> Does that mean the command can only be used with no preconditioner? >> >> http://www.mcs.anl.gov/petsc/**petsc-current/docs/**manualpages/KSP/** >> KSPSetDiagonalScale.html<http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPSetDiagonalScale.html> >> >> All the best, >> >> -- >> Colin McAuliffe >> PhD Candidate >> Columbia University >> Department of Civil Engineering and Engineering Mechanics >> > -- Colin McAuliffe PhD Candidate Columbia University Department of Civil Engineering and Engineering Mechanics
