Re: [petsc-users] GAMG failure

[Blaise Bourdin]

On Mar 27, 2023, at 9:11 PM, Mark Adams <mfad...@lbl.gov> wrote: Yes, the eigen estimates are converging slowly. BTW, have you tried hypre? It is a good solver (lots lots more woman years) These eigen estimates are conceptually simple, but they can lead to problems like this (hypre and an eigen estimate free smoother). I just moved from petsc 3.3 to main, so my experience with an old version of hyper has not been very convincing. Strangely enough, ML has always been the most efficient PC for me. Maybe it’s time to revisit. That said, I would really like to get decent performances out of gamg. One day, I’d like to be able to account for the special structure of phase-field fracture in the construction of the coarse space. But try this (good to have options anyway): -pc_gamg_esteig_ksp_max_it 20 Chevy will scale the estimate that we give by, I think, 5% by default. Maybe 10. You can set that with: -mg_levels_ksp_chebyshev_esteig 0,0.2,0,1.05 0.2 is the scaling of the high eigen estimate for the low eigen value in Chebyshev. Jed’s suggestion of using -pc_gamg_reuse_interpolation 0 worked. I am testing your options at the moment. Thanks a lot, Blaise —  Canada Research Chair in Mathematical and Computational Aspects of Solid Mechanics (Tier 1) Professor, Department of Mathematics & Statistics Hamilton Hall room 409A, McMaster University 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada  https://www.math.mcmaster.ca/bourdin | +1 (905) 525 9140 ext. 27243