Matthew Knepley wrote: > I do not think its fine. I ran with KSP ex10: > > knepley at khan:/PETSc3/petsc/petsc-dev/src/ksp/ksp/examples/tutorials$ ./ex10 > -f0 ~/Desktop/binaryoutput -ksp_monitor -pc_type lu -ksp_type preonly > Number of iterations = 1 > Residual norm 1.12564e+06
Interesting, this instability is highly dependent on the ordering $ ./ex10 -f ~/dl/binaryoutput -ksp_converged_reason -ksp_monitor_singular_value -pc_type lu -pc_factor_mat_ordering_type rcm 0 KSP Residual norm 4.424612243135e+02 % max 1 min 1 max/min 1 1 KSP Residual norm 1.211880345965e-09 % max 1 min 1 max/min 1 Linear solve converged due to CONVERGED_RTOL iterations 1 Number of iterations = 1 Residual norm 0.00398084 also, $ ./ex10 -f ~/dl/binaryoutput -ksp_converged_reason -pc_type lu -pc_factor_mat_solver_package umfpack Linear solve converged due to CONVERGED_RTOL iterations 2 Number of iterations = 2 Residual norm 0.0797212 $ ./ex10 -f ~/dl/binaryoutput -ksp_converged_reason -pc_type lu -pc_factor_mat_solver_package mumps Linear solve converged due to CONVERGED_RTOL iterations 1 Number of iterations = 1 Residual norm 0.00322144 I agree with Matt about trying to reformulate the problem, at least if you need a scalable preconditioner. Jed -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 260 bytes Desc: OpenPGP digital signature URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090516/599b3400/attachment.pgp>
