On Wed, Jan 14, 2009 at 1:54 PM, Nguyen, Hung V ERDC-ITL-MS < Hung.V.Nguyen at usace.army.mil> wrote:
> > Hello All, > > I tried to solve an ill-conditioned system using cg with Jacobi > preconditioned. The KSP solver was stopping due to diverged reason within a > few iterations. Is there a way to keep KSP solver running until max_it? There is no way to continue CG here because it gets a zero divisor, and interprets this as an indefinite matrix. You can try GMRES, however I would first check your matrix using -pc_type lu -ksp_type preonly to make sure its not singular. Matt > > Thanks, > > -hung > > hvnguyen:jade23% aprun -n 16 ./test_matrix_read -ksp_type cg -pc_type > jacobi > -ksp_rtol 1.0e-15 -ksp_max_it 50000 -ksp_monitor -ksp_converged_reason > 0 KSP Residual norm 1.379074550666e+04 > 1 KSP Residual norm 7.252034661743e+03 > 2 KSP Residual norm 7.302184771313e+03 > 3 KSP Residual norm 1.162244351275e+04 > 4 KSP Residual norm 7.912531765659e+03 > 5 KSP Residual norm 4.094706251487e+03 > 6 KSP Residual norm 5.486131070301e+03 > 7 KSP Residual norm 6.367904529202e+03 > 8 KSP Residual norm 6.312767173219e+03 > Linear solve did not converge due to DIVERGED_INDEFINITE_MAT iterations 9 > Time in PETSc solver: 0.452695 seconds > The number of iteration = 9 > The solution residual error = 6.312767e+03 > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090114/9bf1ab5a/attachment.htm>
