Is this problem singular?<br><br><div class="gmail_quote">On Thu, Feb 2, 2012 at 13:47, Thomas Witkowski <span dir="ltr"><<a href="mailto:thomas.witkowski@tu-dresden.de">thomas.witkowski@tu-dresden.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">For some tests I use richardson iterations with direct solver for preconditioning (if everything is fine, richardson should be replaces by preonly).<br>
<br>
-ksp_type richardson -pc_type lu -pc_factor_mat_solver_package mumps -ksp_monitor -ksp_monitor_true_residual -ksp_max_it 10<br>
<br>
For some matrices I see that it converges fine in true residual norm but not in the preconditioned one:<br>
<br>
0 KSP Residual norm 1.540366130785e+05<br>
0 KSP preconditioned resid norm 1.540366130785e+05 true resid norm 4.257656834616e+04 ||r(i)||/||b|| 1.000000000000e+00<br>
1 KSP Residual norm 1.355077212761e+05<br>
1 KSP preconditioned resid norm 1.355077212761e+05 true resid norm 1.468758291284e-11 ||r(i)||/||b|| 3.449686877867e-16<br>
2 KSP Residual norm 3.775360693480e+05<br>
2 KSP preconditioned resid norm 3.775360693480e+05 true resid norm 5.008860262312e-12 ||r(i)||/||b|| 1.176435879376e-16<br>
3 KSP Residual norm 1.714431257209e+05<br>
3 KSP preconditioned resid norm 1.714431257209e+05 true resid norm 5.365631839419e-12 ||r(i)||/||b|| 1.260231166541e-16<br>
4 KSP Residual norm 7.164219897555e+04<br>
4 KSP preconditioned resid norm 7.164219897555e+04 true resid norm 5.582291603774e-12 ||r(i)||/||b|| 1.311118256030e-16<br>
5 KSP Residual norm 2.480147180914e+05<br>
5 KSP preconditioned resid norm 2.480147180914e+05 true resid norm 5.464714292269e-12 ||r(i)||/||b|| 1.283502758569e-16<br>
6 KSP Residual norm 1.749548383255e+05<br>
6 KSP preconditioned resid norm 1.749548383255e+05 true resid norm 6.601924132117e-12 ||r(i)||/||b|| 1.550600339239e-16<br>
7 KSP Residual norm 1.873773824295e+05<br>
7 KSP preconditioned resid norm 1.873773824295e+05 true resid norm 6.368611865551e-12 ||r(i)||/||b|| 1.495802060366e-16<br>
8 KSP Residual norm 2.610223461339e+05<br>
8 KSP preconditioned resid norm 2.610223461339e+05 true resid norm 8.365362648969e-12 ||r(i)||/||b|| 1.964780858090e-16<br>
9 KSP Residual norm 2.459609758347e+05<br>
9 KSP preconditioned resid norm 2.459609758347e+05 true resid norm 8.427381039077e-12 ||r(i)||/||b|| 1.979347177668e-16<br>
10 KSP Residual norm 1.611793769272e+05<br>
10 KSP preconditioned resid norm 1.611793769272e+05 true resid norm 8.325158481093e-12 ||r(i)||/||b|| 1.955338066095e-16<br>
<br>
<br>
Would could be the reason for?<br><font color="#888888">
<br>
Thomas<br>
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