Is this problem singular? On Thu, Feb 2, 2012 at 13:47, Thomas Witkowski < thomas.witkowski at tu-dresden.de> wrote:
> For some tests I use richardson iterations with direct solver for > preconditioning (if everything is fine, richardson should be replaces by > preonly). > > -ksp_type richardson -pc_type lu -pc_factor_mat_solver_package mumps > -ksp_monitor -ksp_monitor_true_residual -ksp_max_it 10 > > For some matrices I see that it converges fine in true residual norm but > not in the preconditioned one: > > 0 KSP Residual norm 1.540366130785e+05 > 0 KSP preconditioned resid norm 1.540366130785e+05 true resid norm > 4.257656834616e+04 ||r(i)||/||b|| 1.000000000000e+00 > 1 KSP Residual norm 1.355077212761e+05 > 1 KSP preconditioned resid norm 1.355077212761e+05 true resid norm > 1.468758291284e-11 ||r(i)||/||b|| 3.449686877867e-16 > 2 KSP Residual norm 3.775360693480e+05 > 2 KSP preconditioned resid norm 3.775360693480e+05 true resid norm > 5.008860262312e-12 ||r(i)||/||b|| 1.176435879376e-16 > 3 KSP Residual norm 1.714431257209e+05 > 3 KSP preconditioned resid norm 1.714431257209e+05 true resid norm > 5.365631839419e-12 ||r(i)||/||b|| 1.260231166541e-16 > 4 KSP Residual norm 7.164219897555e+04 > 4 KSP preconditioned resid norm 7.164219897555e+04 true resid norm > 5.582291603774e-12 ||r(i)||/||b|| 1.311118256030e-16 > 5 KSP Residual norm 2.480147180914e+05 > 5 KSP preconditioned resid norm 2.480147180914e+05 true resid norm > 5.464714292269e-12 ||r(i)||/||b|| 1.283502758569e-16 > 6 KSP Residual norm 1.749548383255e+05 > 6 KSP preconditioned resid norm 1.749548383255e+05 true resid norm > 6.601924132117e-12 ||r(i)||/||b|| 1.550600339239e-16 > 7 KSP Residual norm 1.873773824295e+05 > 7 KSP preconditioned resid norm 1.873773824295e+05 true resid norm > 6.368611865551e-12 ||r(i)||/||b|| 1.495802060366e-16 > 8 KSP Residual norm 2.610223461339e+05 > 8 KSP preconditioned resid norm 2.610223461339e+05 true resid norm > 8.365362648969e-12 ||r(i)||/||b|| 1.964780858090e-16 > 9 KSP Residual norm 2.459609758347e+05 > 9 KSP preconditioned resid norm 2.459609758347e+05 true resid norm > 8.427381039077e-12 ||r(i)||/||b|| 1.979347177668e-16 > 10 KSP Residual norm 1.611793769272e+05 > 10 KSP preconditioned resid norm 1.611793769272e+05 true resid norm > 8.325158481093e-12 ||r(i)||/||b|| 1.955338066095e-16 > > > Would could be the reason for? > > Thomas > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120202/8fd77cab/attachment.htm>
