On Fri, Aug 15, 2008 at 5:40 PM, Lukasz Kaczmarczyk <lukasz at civil.gla.ac.uk> wrote: > Barry Smith wrote: >> 9 KSP Residual norm 3.942287795560e-03 >> 10 KSP Residual norm 4.611215310185e+00 >> ^^^^^^^^^^^^^^^^^^^^^^ >> >> This should never happen. This means there is an error >> in your preconditioner, your smoother is not a linear operator >> on its input variables. With GMRES, at restart the residual >> norm should hardly change at all. The fact that it shoots >> up means that the norm indicated in iteration 9 is totally wrong. >> >> If you run the gmres version with -ksp_monitor_true_residual >> you will see that the true residual is not actually decreasing >> like you think it is. >> > > Thank You for answer, result for which you asking are in my previous > email - look at end of the previous email. If You look there at true > residual, You will see that results are ok.
That is not the point. The residual may be decreasing, but your PC is not a linear operator, and thus you can encounter unexpected results with GMRES. You can switch to FGMRES to handle this. Matt > Regards, > Lukasz > > 2) -ksp_type fgmres -ksp_gmres_restart 100 -ksp_monitor_true_residual > 0 KSP preconditioned resid norm 8.770931682456e+05 true resid norm > 8.770931682456e+05 ||Ae||/||Ax|| 2.025559907164e+06 > 1 KSP preconditioned resid norm 1.466659768959e+00 true resid norm > 1.466659768959e+00 ||Ae||/||Ax|| 3.387105649673e+00 > 2 KSP preconditioned resid norm 2.135783619677e-01 true resid norm > 2.135783619678e-01 ||Ae||/||Ax|| 4.932380991006e-01 > 3 KSP preconditioned resid norm 1.342354228152e-01 true resid norm > 1.342354228151e-01 ||Ae||/||Ax|| 3.100034299884e-01 > 4 KSP preconditioned resid norm 7.872906297489e-02 true resid norm > 7.872906297491e-02 ||Ae||/||Ax|| 1.818169828064e-01 > 5 KSP preconditioned resid norm 3.414496482864e-02 true resid norm > 3.414496482865e-02 ||Ae||/||Ax|| 7.885441854116e-02 > 6 KSP preconditioned resid norm 2.025183908090e-02 true resid norm > 2.025183908092e-02 ||Ae||/||Ax|| 4.676961897981e-02 > 7 KSP preconditioned resid norm 1.023707179274e-02 true resid norm > 1.023707179279e-02 ||Ae||/||Ax|| 2.364150462111e-02 > 8 KSP preconditioned resid norm 4.938281368004e-03 true resid norm > 4.938281368031e-03 ||Ae||/||Ax|| 1.140447230867e-02 > 9 KSP preconditioned resid norm 2.373276511281e-03 true resid norm > 2.373276511245e-03 ||Ae||/||Ax|| 5.480847330515e-03 > 10 KSP preconditioned resid norm 1.180493643594e-03 true resid norm > 1.180493643635e-03 ||Ae||/||Ax|| 2.726233291716e-03 > 11 KSP preconditioned resid norm 7.142592937639e-04 true resid norm > 7.142592936809e-04 ||Ae||/||Ax|| 1.649511181911e-03 > 12 KSP preconditioned resid norm 4.226036746778e-04 true resid norm > > > 3) -ksp_type fgmres -ksp_gmres_restart 10 -ksp_monitor_true_residual > 0 KSP preconditioned resid norm 8.770931682456e+05 true resid norm > 8.770931682456e+05 ||Ae||/||Ax|| 2.025559907164e+06 > 1 KSP preconditioned resid norm 1.466659768959e+00 true resid norm > 1.466659768959e+00 ||Ae||/||Ax|| 3.387105649673e+00 > 2 KSP preconditioned resid norm 2.135783619677e-01 true resid norm > 2.135783619678e-01 ||Ae||/||Ax|| 4.932380991006e-01 > 3 KSP preconditioned resid norm 1.342354228152e-01 true resid norm > 1.342354228151e-01 ||Ae||/||Ax|| 3.100034299884e-01 > 4 KSP preconditioned resid norm 7.872906297489e-02 true resid norm > 7.872906297491e-02 ||Ae||/||Ax|| 1.818169828064e-01 > 5 KSP preconditioned resid norm 3.414496482864e-02 true resid norm > 3.414496482865e-02 ||Ae||/||Ax|| 7.885441854116e-02 > 6 KSP preconditioned resid norm 2.025183908090e-02 true resid norm > 2.025183908092e-02 ||Ae||/||Ax|| 4.676961897981e-02 > 7 KSP preconditioned resid norm 1.023707179274e-02 true resid norm > 1.023707179279e-02 ||Ae||/||Ax|| 2.364150462111e-02 > 8 KSP preconditioned resid norm 4.938281368004e-03 true resid norm > 4.938281368031e-03 ||Ae||/||Ax|| 1.140447230867e-02 > 9 KSP preconditioned resid norm 2.373276511281e-03 true resid norm > 2.373276511245e-03 ||Ae||/||Ax|| 5.480847330515e-03 > 10 KSP preconditioned resid norm 1.180493643635e-03 true resid norm > 1.180493643635e-03 ||Ae||/||Ax|| 2.726233291716e-03 > 11 KSP preconditioned resid norm 8.973593571160e-04 true resid norm > 8.973593570913e-04 ||Ae||/||Ax|| 2.072362665506e-03 > 12 KSP preconditioned resid norm 8.954054180580e-04 true resid norm > > > -- 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
