Sorry for the delay. The problem is that the eigen estimates are bad for the Chebyshev smoother. Unfortunately this fails catastrophically.
First, I do not understand why we do not get an error message here: 13:57 PICell> ~/Codes/petsc/src/ksp/ksp/examples/tutorials$ mpirun -n 8 ./ex54 -ne 1023 -ksp_rtol 1e-10 -ksp_monitor_true_residual -options_left 0 KSP preconditioned resid norm 2.408779787997e+03 true resid norm 9.779947596963e-04 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 6.605106317291e+01 true resid norm 6.550622855055e-02 ||r(i)||/||b|| 6.698014268593e+01 2 KSP preconditioned resid norm 2.105905914541e+01 true resid norm 5.536477156386e-03 ||r(i)||/||b|| 5.661049920253e+00 3 KSP preconditioned resid norm 2.775390521485e+00 true resid norm 1.822171753713e-03 ||r(i)||/||b|| 1.863171285579e+00 4 KSP preconditioned resid norm 6.367933585867e-01 true resid norm 2.173992967507e-03 ||r(i)||/||b|| 2.222908605545e+00 #PETSc Option Table entries: -ksp_monitor_true_residual -ksp_rtol 1e-10 -ne 1023 -options_left #End of PETSc Option Table entries There are no unused options. It just stops. What is going on here????? A problem is that GMRES is the default it is not accuare. CG is much better. I will add this to all tests (54, 55, 56) that use Cheby. Here is what we get with CG: 14:12 PICell> ~/Codes/petsc/src/ksp/ksp/examples/tutorials$ mpirun -n 8 ./ex54 -ne 1023 -ksp_rtol 1e-10 -ksp_monitor_true_residual -mg_levels_esteig_ksp_type cg 0 KSP preconditioned resid norm 2.397141111771e+03 true resid norm 9.779947596963e-04 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 6.398367771703e+01 true resid norm 5.969698581458e-02 ||r(i)||/||b|| 6.104018986064e+01 2 KSP preconditioned resid norm 2.025487152015e+01 true resid norm 4.795534114089e-03 ||r(i)||/||b|| 4.903435388118e+00 3 KSP preconditioned resid norm 2.693141357521e+00 true resid norm 1.392786125856e-03 ||r(i)||/||b|| 1.424124323824e+00 4 KSP preconditioned resid norm 6.147511674674e-01 true resid norm 2.801964778489e-04 ||r(i)||/||b|| 2.865010012281e-01 5 KSP preconditioned resid norm 1.133515586579e-01 true resid norm 3.760895077288e-05 ||r(i)||/||b|| 3.845516594031e-02 6 KSP preconditioned resid norm 1.169295614319e-02 true resid norm 5.672568123760e-06 ||r(i)||/||b|| 5.800202984239e-03 7 KSP preconditioned resid norm 1.281609546752e-03 true resid norm 8.103035520325e-07 ||r(i)||/||b|| 8.285356787434e-04 8 KSP preconditioned resid norm 1.898415766718e-04 true resid norm 1.250723051310e-07 ||r(i)||/||b|| 1.278864778067e-04 9 KSP preconditioned resid norm 3.325790135426e-05 true resid norm 2.304415060174e-08 ||r(i)||/||b|| 2.356265243067e-05 10 KSP preconditioned resid norm 8.224698701048e-06 true resid norm 4.786148212120e-09 ||r(i)||/||b|| 4.893838299917e-06 11 KSP preconditioned resid norm 1.224414108364e-06 true resid norm 7.170267325093e-10 ||r(i)||/||b|| 7.331600966164e-07 12 KSP preconditioned resid norm 1.760480053719e-07 true resid norm 1.005681798001e-10 ||r(i)||/||b|| 1.028310006807e-07 So all is well. Thanks for pointing this out. Mark On Thu, Jul 2, 2015 at 5:38 PM, Benoit Fabrèges <[email protected]> wrote: > Dear PETSc developers, > I updated from 3.4 to 3.6 and I have a strange behavior with the GAMG > preconditioner. I am running ex54 with the following options: > -ne 1023 -ksp_rtol 1e-10 -ksp_monitor_true_residual -options_left > > I don't have the same behavior depending on the number of process used. It > is for example not converging with 8 and 12 process with the reason > KSP_DIVERGED_INDEFINITE_PC but it is working fine in other cases (I didn't > try with more than 12 process). > > Do you have the same behavior ? It is working fine with 3.4 version. > > Best, > > Benoit > > > >
