This looks good: $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 2 -mg_levels_pc_type sor lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 10 Linear solve converged due to CONVERGED_RTOL iterations 7 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 9 Linear solve converged due to CONVERGED_RTOL iterations 9 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 7 Number of SNES iterations = 9 I assume it is independent of the number of levels of refinement? Note that you could use -pc_type eisenstat perhaps in this case instead. Might save lots of flops? I've often wondered about doing Mark's favorite chebyshev smoother with Eisenstat, seems like it should be a good match. Barry On May 23, 2012, at 11:48 AM, Jed Brown wrote:

If ex19 is what matters...

$ base='mpiexec.hydra -n 4 ./ex19 -da_refine 3 -lidvelocity 100 -grashof 1e4 -pc_type mg -ksp_type fgmres -pc_mg_type full -ksp_converged_reason' $ $base lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 23 Linear solve converged due to CONVERGED_RTOL iterations 12 Linear solve converged due to CONVERGED_RTOL iterations 12 Linear solve converged due to CONVERGED_RTOL iterations 17 Linear solve converged due to CONVERGED_RTOL iterations 15 Linear solve converged due to CONVERGED_RTOL iterations 13 Linear solve converged due to CONVERGED_RTOL iterations 19 Linear solve converged due to CONVERGED_RTOL iterations 21 Linear solve converged due to CONVERGED_RTOL iterations 18 Number of SNES iterations = 9 $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 1 -mg_levels_pc_type pbjacobi lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 25 Linear solve converged due to CONVERGED_RTOL iterations 27 Linear solve converged due to CONVERGED_RTOL iterations 27 Linear solve converged due to CONVERGED_RTOL iterations 30 Linear solve converged due to CONVERGED_RTOL iterations 28 Linear solve converged due to CONVERGED_RTOL iterations 42 Linear solve converged due to CONVERGED_RTOL iterations 49 Linear solve converged due to CONVERGED_RTOL iterations 52 Linear solve converged due to CONVERGED_RTOL iterations 48 Number of SNES iterations = 9 $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 1 -mg_levels_pc_type sor lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 22 Linear solve converged due to CONVERGED_RTOL iterations 16 Linear solve converged due to CONVERGED_RTOL iterations 17 Linear solve converged due to CONVERGED_RTOL iterations 19 Linear solve converged due to CONVERGED_RTOL iterations 19 Linear solve converged due to CONVERGED_RTOL iterations 17 Linear solve converged due to CONVERGED_RTOL iterations 20 Linear solve converged due to CONVERGED_RTOL iterations 18 Linear solve converged due to CONVERGED_RTOL iterations 17 Number of SNES iterations = 9 $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 2 -mg_levels_pc_type pbjacobi lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 15 Linear solve converged due to CONVERGED_RTOL iterations 13 Linear solve converged due to CONVERGED_RTOL iterations 16 Linear solve converged due to CONVERGED_RTOL iterations 15 Linear solve converged due to CONVERGED_RTOL iterations 16 Linear solve converged due to CONVERGED_RTOL iterations 16 Linear solve converged due to CONVERGED_RTOL iterations 18 Linear solve converged due to CONVERGED_RTOL iterations 17 Linear solve converged due to CONVERGED_RTOL iterations 16 Number of SNES iterations = 9 $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 2 -mg_levels_pc_type sor lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 10 Linear solve converged due to CONVERGED_RTOL iterations 7 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 9 Linear solve converged due to CONVERGED_RTOL iterations 9 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 8 Linear solve converged due to CONVERGED_RTOL iterations 7 Number of SNES iterations = 9 $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 3 -mg_levels_pc_type pbjacobi lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 12 Linear solve converged due to CONVERGED_RTOL iterations 9 Linear solve converged due to CONVERGED_RTOL iterations 11 Linear solve converged due to CONVERGED_RTOL iterations 11 Linear solve converged due to CONVERGED_RTOL iterations 11 Linear solve converged due to CONVERGED_RTOL iterations 12 Linear solve converged due to CONVERGED_RTOL iterations 12 Linear solve converged due to CONVERGED_RTOL iterations 11 Linear solve converged due to CONVERGED_RTOL iterations 11 Number of SNES iterations = 9 $ $base -mg_levels_ksp_type chebyshev -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.1,1.1 -mg_levels_ksp_max_it 3 -mg_levels_pc_type sor lid velocity = 100, prandtl # = 1, grashof # = 10000 Linear solve converged due to CONVERGED_RTOL iterations 9 Linear solve converged due to CONVERGED_RTOL iterations 6 Linear solve converged due to CONVERGED_RTOL iterations 6 Linear solve converged due to CONVERGED_RTOL iterations 7 Linear solve converged due to CONVERGED_RTOL iterations 7 Linear solve converged due to CONVERGED_RTOL iterations 6 Linear solve converged due to CONVERGED_RTOL iterations 7 Linear solve converged due to CONVERGED_RTOL iterations 6 Linear solve converged due to CONVERGED_RTOL iterations 6 Number of SNES iterations = 9