Barry Smith wrote: > > On Aug 14, 2008, at 5:09 PM, Lukasz Kaczmarczyk wrote: > >> Hello, >> I have implementation of geometric multi-grid for heterogeneous >> quasi-brittle materials for hybrid-trefftz finite elements (degrees of >> freedom are on faces -> small number of neighbours). Multi-grid >> algorithm need smoothing, for that I use Gauss-Seidel, however SOR >> implemented in PETSc is not parallel. That is way, I implemented my own >> parallel Gauss-Seidel with colouring of faces in order to reduce >> communication. Everything seems to work prefect, except that that for >> GMRES after restart algorithm is divergent. > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > What do you mean? It is converging fine until you hit the restart > iteration and > then get a totally different residual norm? And then each iteration gives > worse residuals?
Thanks You all for response. No, algorithm is stable to next restart > > Please run with -ksp_monitor_true_residual and send the output. > If the preconditioner is not actually a linear operator (i.e. it has a > bug in > smoother) then the residual norm computed in GMRES may be wrong > and so GMRES may look like it is working but actually is basically > chugging on garbage. Also run with -ksp_type fgmres > -ksp_monitor_true_residual > and send the output. > I hope that this helps, I send three outputs: 1) -ksp_type gmres -ksp_gmres_restart 10 2) -ksp_type fgmres -ksp_gmres_restart 100 -ksp_monitor_true_residual 3) -ksp_type fgmres -ksp_gmres_restart 10 -ksp_monitor_true_residual 1) ksp_type gmres -ksp_gmres_restart 10 0 KSP Residual norm 2.604671539574e+02 1 KSP Residual norm 8.673339524769e+00 2 KSP Residual norm 1.854343060681e+00 3 KSP Residual norm 4.635172307027e-01 4 KSP Residual norm 1.824358407207e-01 5 KSP Residual norm 9.823366032782e-02 6 KSP Residual norm 5.859833143089e-02 7 KSP Residual norm 2.929617664041e-02 8 KSP Residual norm 1.184403532587e-02 9 KSP Residual norm 3.942287795560e-03 10 KSP Residual norm 4.611215310185e+00 11 KSP Residual norm 3.557713305907e-01 12 KSP Residual norm 1.911999331832e-01 13 KSP Residual norm 1.048287519555e-01 14 KSP Residual norm 5.745962963315e-02 15 KSP Residual norm 5.238562834476e-02 16 KSP Residual norm 5.046872351948e-02 17 KSP Residual norm 5.041805668527e-02 18 KSP Residual norm 4.952005417494e-02 19 KSP Residual norm 4.950805199415e-02 20 KSP Residual norm 8.581369434072e+00 21 KSP Residual norm 8.168490133118e-01 22 KSP Residual norm 1.416002910406e-01 23 KSP Residual norm 6.679961898612e-02 24 KSP Residual norm 5.031183883430e-02 25 KSP Residual norm 4.670843908572e-02 26 KSP Residual norm 4.662064456590e-02 27 KSP Residual norm 4.652217965668e-02 28 KSP Residual norm 4.611529866498e-02 29 KSP Residual norm 4.610330586416e-02 30 KSP Residual norm 9.139117000729e+00 31 KSP Residual norm 1.170939505327e+00 32 KSP Residual norm 1.783857007759e-01 33 KSP Residual norm 1.413658128682e-01 34 KSP Residual norm 1.411820201886e-01 35 KSP Residual norm 1.372634877051e-01 2) -ksp_type fgmres -ksp_gmres_restart 100 -ksp_monitor_true_residual 0 KSP Residual norm 8.770931682456e+05 0 KSP preconditioned resid norm 8.770931682456e+05 true resid norm 8.770931682456e+05 ||Ae||/||Ax|| 2.025559907164e+06 1 KSP Residual norm 1.466659768959e+00 1 KSP preconditioned resid norm 1.466659768959e+00 true resid norm 1.466659768959e+00 ||Ae||/||Ax|| 3.387105649673e+00 2 KSP Residual norm 2.135783619677e-01 2 KSP preconditioned resid norm 2.135783619677e-01 true resid norm 2.135783619678e-01 ||Ae||/||Ax|| 4.932380991006e-01 3 KSP Residual norm 1.342354228152e-01 3 KSP preconditioned resid norm 1.342354228152e-01 true resid norm 1.342354228151e-01 ||Ae||/||Ax|| 3.100034299884e-01 4 KSP Residual norm 7.872906297489e-02 4 KSP preconditioned resid norm 7.872906297489e-02 true resid norm 7.872906297491e-02 ||Ae||/||Ax|| 1.818169828064e-01 5 KSP Residual norm 3.414496482864e-02 5 KSP preconditioned resid norm 3.414496482864e-02 true resid norm 3.414496482865e-02 ||Ae||/||Ax|| 7.885441854116e-02 6 KSP Residual norm 2.025183908090e-02 6 KSP preconditioned resid norm 2.025183908090e-02 true resid norm 2.025183908092e-02 ||Ae||/||Ax|| 4.676961897981e-02 7 KSP Residual norm 1.023707179274e-02 7 KSP preconditioned resid norm 1.023707179274e-02 true resid norm 1.023707179279e-02 ||Ae||/||Ax|| 2.364150462111e-02 8 KSP Residual norm 4.938281368004e-03 8 KSP preconditioned resid norm 4.938281368004e-03 true resid norm 4.938281368031e-03 ||Ae||/||Ax|| 1.140447230867e-02 9 KSP Residual norm 2.373276511281e-03 9 KSP preconditioned resid norm 2.373276511281e-03 true resid norm 2.373276511245e-03 ||Ae||/||Ax|| 5.480847330515e-03 10 KSP Residual norm 1.180493643594e-03 10 KSP preconditioned resid norm 1.180493643594e-03 true resid norm 1.180493643635e-03 ||Ae||/||Ax|| 2.726233291716e-03 11 KSP Residual norm 7.142592937639e-04 11 KSP preconditioned resid norm 7.142592937639e-04 true resid norm 7.142592936809e-04 ||Ae||/||Ax|| 1.649511181911e-03 12 KSP Residual norm 4.226036746778e-04 12 KSP preconditioned resid norm 4.226036746778e-04 true resid norm 4.226036746206e-04 ||Ae||/||Ax|| 9.759613812110e-04 13 KSP Residual norm 2.572539106719e-04 13 KSP preconditioned resid norm 2.572539106719e-04 true resid norm 2.572539106261e-04 ||Ae||/||Ax|| 5.941024582002e-04 14 KSP Residual norm 1.444791718863e-04 14 KSP preconditioned resid norm 1.444791718863e-04 true resid norm 1.444791718510e-04 ||Ae||/||Ax|| 3.336603550419e-04 15 KSP Residual norm 8.492790274639e-05 15 KSP preconditioned resid norm 8.492790274639e-05 true resid norm 8.492790267409e-05 ||Ae||/||Ax|| 1.961325898824e-04 16 KSP Residual norm 4.707269600494e-05 16 KSP preconditioned resid norm 4.707269600494e-05 true resid norm 4.707269601177e-05 ||Ae||/||Ax|| 1.087097348555e-04 17 KSP Residual norm 2.692621130650e-05 17 KSP preconditioned resid norm 2.692621130650e-05 true resid norm 2.692621130585e-05 ||Ae||/||Ax|| 6.218342138276e-05 18 KSP Residual norm 1.339283607815e-05 18 KSP preconditioned resid norm 1.339283607815e-05 true resid norm 1.339283617815e-05 ||Ae||/||Ax|| 3.092943029068e-05 19 KSP Residual norm 8.006569523728e-06 19 KSP preconditioned resid norm 8.006569523728e-06 true resid norm 8.006569546889e-06 ||Ae||/||Ax|| 1.849038033273e-05 20 KSP Residual norm 5.048620120372e-06 20 KSP preconditioned resid norm 5.048620120372e-06 true resid norm 5.048620165524e-06 ||Ae||/||Ax|| 1.165928884641e-05 21 KSP Residual norm 3.079047055409e-06 21 KSP preconditioned resid norm 3.079047055409e-06 true resid norm 3.079047092852e-06 ||Ae||/||Ax|| 7.110754671622e-06 22 KSP Residual norm 1.837917124370e-06 22 KSP preconditioned resid norm 1.837917124370e-06 true resid norm 1.837917088425e-06 ||Ae||/||Ax|| 4.244487703000e-06 23 KSP Residual norm 8.755715968227e-07 23 KSP preconditioned resid norm 8.755715968227e-07 true resid norm 8.755715746951e-07 ||Ae||/||Ax|| 2.022045937380e-06 24 KSP Residual norm 4.460215115186e-07 24 KSP preconditioned resid norm 4.460215115186e-07 true resid norm 4.460215473811e-07 ||Ae||/||Ax|| 1.030042641779e-06 25 KSP Residual norm 2.074601204717e-07 25 KSP preconditioned resid norm 2.074601204717e-07 true resid norm 2.074601610498e-07 ||Ae||/||Ax|| 4.791087193129e-07 26 KSP Residual norm 1.078594582430e-07 26 KSP preconditioned resid norm 1.078594582430e-07 true resid norm 1.078594313079e-07 ||Ae||/||Ax|| 2.490906868011e-07 27 KSP Residual norm 5.595789534852e-08 27 KSP preconditioned resid norm 5.595789534852e-08 true resid norm 5.595808793116e-08 ||Ae||/||Ax|| 1.292296685216e-07 28 KSP Residual norm 2.866350154035e-08 28 KSP preconditioned resid norm 2.866350154035e-08 true resid norm 2.866379598785e-08 ||Ae||/||Ax|| 6.619620131833e-08 29 KSP Residual norm 1.602353949308e-08 29 KSP preconditioned resid norm 1.602353949308e-08 true resid norm 1.602386060096e-08 ||Ae||/||Ax|| 3.700552092568e-08 30 KSP Residual norm 8.795011075741e-09 30 KSP preconditioned resid norm 8.795011075741e-09 true resid norm 8.795292666765e-09 ||Ae||/||Ax|| 2.031185835503e-08 31 KSP Residual norm 4.077129947799e-09 31 KSP preconditioned resid norm 4.077129947799e-09 true resid norm 4.079852425518e-09 ||Ae||/||Ax|| 9.422015584506e-09 32 KSP Residual norm 1.739123114987e-09 32 KSP preconditioned resid norm 1.739123114987e-09 true resid norm 1.743717145343e-09 ||Ae||/||Ax|| 4.026942253017e-09 33 KSP Residual norm 8.452345380894e-10 33 KSP preconditioned resid norm 8.452345380894e-10 true resid norm 8.816532993133e-10 ||Ae||/||Ax|| 2.036091078762e-09 34 KSP Residual norm 3.861058363559e-10 34 KSP preconditioned resid norm 3.861058363559e-10 true resid norm 3.853896597046e-10 ||Ae||/||Ax|| 8.900192950935e-10 35 KSP Residual norm 1.986142320978e-10 3) -ksp_type fgmres -ksp_gmres_restart 10 -ksp_monitor_true_residual 0 KSP Residual norm 8.770931682456e+05 0 KSP preconditioned resid norm 8.770931682456e+05 true resid norm 8.770931682456e+05 ||Ae||/||Ax|| 2.025559907164e+06 1 KSP Residual norm 1.466659768959e+00 1 KSP preconditioned resid norm 1.466659768959e+00 true resid norm 1.466659768959e+00 ||Ae||/||Ax|| 3.387105649673e+00 2 KSP Residual norm 2.135783619677e-01 2 KSP preconditioned resid norm 2.135783619677e-01 true resid norm 2.135783619678e-01 ||Ae||/||Ax|| 4.932380991006e-01 3 KSP Residual norm 1.342354228152e-01 3 KSP preconditioned resid norm 1.342354228152e-01 true resid norm 1.342354228151e-01 ||Ae||/||Ax|| 3.100034299884e-01 4 KSP Residual norm 7.872906297489e-02 4 KSP preconditioned resid norm 7.872906297489e-02 true resid norm 7.872906297491e-02 ||Ae||/||Ax|| 1.818169828064e-01 5 KSP Residual norm 3.414496482864e-02 5 KSP preconditioned resid norm 3.414496482864e-02 true resid norm 3.414496482865e-02 ||Ae||/||Ax|| 7.885441854116e-02 6 KSP Residual norm 2.025183908090e-02 6 KSP preconditioned resid norm 2.025183908090e-02 true resid norm 2.025183908092e-02 ||Ae||/||Ax|| 4.676961897981e-02 7 KSP Residual norm 1.023707179274e-02 7 KSP preconditioned resid norm 1.023707179274e-02 true resid norm 1.023707179279e-02 ||Ae||/||Ax|| 2.364150462111e-02 8 KSP Residual norm 4.938281368004e-03 8 KSP preconditioned resid norm 4.938281368004e-03 true resid norm 4.938281368031e-03 ||Ae||/||Ax|| 1.140447230867e-02 9 KSP Residual norm 2.373276511281e-03 9 KSP preconditioned resid norm 2.373276511281e-03 true resid norm 2.373276511245e-03 ||Ae||/||Ax|| 5.480847330515e-03 10 KSP Residual norm 1.180493643635e-03 10 KSP preconditioned resid norm 1.180493643635e-03 true resid norm 1.180493643635e-03 ||Ae||/||Ax|| 2.726233291716e-03 11 KSP Residual norm 8.973593571160e-04 11 KSP preconditioned resid norm 8.973593571160e-04 true resid norm 8.973593570913e-04 ||Ae||/||Ax|| 2.072362665506e-03 12 KSP Residual norm 8.954054180580e-04 12 KSP preconditioned resid norm 8.954054180580e-04 true resid norm 8.954054180762e-04 ||Ae||/||Ax|| 2.067850236641e-03 13 KSP Residual norm 8.509609619524e-04 13 KSP preconditioned resid norm 8.509609619524e-04 true resid norm 8.509609619593e-04 ||Ae||/||Ax|| 1.965210161828e-03 14 KSP Residual norm 8.458566359370e-04 14 KSP preconditioned resid norm 8.458566359370e-04 true resid norm 8.458566359291e-04 ||Ae||/||Ax|| 1.953422225798e-03 15 KSP Residual norm 8.372984660266e-04 15 KSP preconditioned resid norm 8.372984660266e-04 true resid norm 8.372984660471e-04 ||Ae||/||Ax|| 1.933657979058e-03 16 KSP Residual norm 7.279198160941e-04 16 KSP preconditioned resid norm 7.279198160941e-04 true resid norm 7.279198160961e-04 ||Ae||/||Ax|| 1.681058807086e-03 17 KSP Residual norm 7.254072398644e-04 17 KSP preconditioned resid norm 7.254072398644e-04 true resid norm 7.254072398528e-04 ||Ae||/||Ax|| 1.675256260804e-03 18 KSP Residual norm 6.813582761007e-04 18 KSP preconditioned resid norm 6.813582761007e-04 true resid norm 6.813582760932e-04 ||Ae||/||Ax|| 1.573529536468e-03 19 KSP Residual norm 5.556242867367e-04 19 KSP preconditioned resid norm 5.556242867367e-04 true resid norm 5.556242867546e-04 ||Ae||/||Ax|| 1.283159326104e-03 20 KSP Residual norm 4.379413135337e-04 20 KSP preconditioned resid norm 4.379413135337e-04 true resid norm 4.379413135337e-04 ||Ae||/||Ax|| 1.011382141032e-03 21 KSP Residual norm 4.159789873039e-04 21 KSP preconditioned resid norm 4.159789873039e-04 true resid norm 4.159789873292e-04 ||Ae||/||Ax|| 9.606623212470e-04 22 KSP Residual norm 3.988218089618e-04 22 KSP preconditioned resid norm 3.988218089618e-04 true resid norm 3.988218089773e-04 ||Ae||/||Ax|| 9.210395150869e-04 23 KSP Residual norm 3.981102611370e-04 23 KSP preconditioned resid norm 3.981102611370e-04 true resid norm 3.981102611544e-04 ||Ae||/||Ax|| 9.193962657785e-04 24 KSP Residual norm 3.619785012910e-04 24 KSP preconditioned resid norm 3.619785012910e-04 true resid norm 3.619785013142e-04 ||Ae||/||Ax|| 8.359535406984e-04 25 KSP Residual norm 3.351791646576e-04 25 KSP preconditioned resid norm 3.351791646576e-04 true resid norm 3.351791646837e-04 ||Ae||/||Ax|| 7.740631238275e-04 26 KSP Residual norm 3.051027323014e-04 26 KSP preconditioned resid norm 3.051027323014e-04 true resid norm 3.051027323283e-04 ||Ae||/||Ax|| 7.046045785610e-04 27 KSP Residual norm 2.977852161346e-04 27 KSP preconditioned resid norm 2.977852161346e-04 true resid norm 2.977852161482e-04 ||Ae||/||Ax|| 6.877054988155e-04 28 KSP Residual norm 2.507200839706e-04 28 KSP preconditioned resid norm 2.507200839706e-04 true resid norm 2.507200839354e-04 ||Ae||/||Ax|| 5.790132318055e-04 29 KSP Residual norm 1.792952379074e-04 29 KSP preconditioned resid norm 1.792952379074e-04 true resid norm 1.792952379357e-04 ||Ae||/||Ax|| 4.140646155464e-04 30 KSP Residual norm 1.539920471163e-04 30 KSP preconditioned resid norm 1.539920471163e-04 true resid norm 1.539920471163e-04 ||Ae||/||Ax|| 3.556293994227e-04 31 KSP Residual norm 1.538529289011e-04 31 KSP preconditioned resid norm 1.538529289011e-04 true resid norm 1.538529288671e-04 ||Ae||/||Ax|| 3.553081195881e-04 32 KSP Residual norm 1.504592268331e-04 32 KSP preconditioned resid norm 1.504592268331e-04 true resid norm 1.504592268204e-04 ||Ae||/||Ax|| 3.474707004273e-04 33 KSP Residual norm 1.504404986449e-04 33 KSP preconditioned resid norm 1.504404986449e-04 true resid norm 1.504404986576e-04 ||Ae||/||Ax|| 3.474274495880e-04 34 KSP Residual norm 1.411298358801e-04 34 KSP preconditioned resid norm 1.411298358801e-04 true resid norm 1.411298358680e-04 ||Ae||/||Ax|| 3.259253949163e-04 35 KSP Residual norm 1.128668990420e-04
