You can -pc_gamg_threshold .02 to slow the coarsening and either stronger smoother or increase number of iterations used for estimation (or increase tolerance). I assume your system is SPD and you've set the near-null space.
Blaise Bourdin <bour...@mcmaster.ca> writes: > Hi, > > I am having issue with GAMG for some very ill-conditioned 2D linearized > elasticity problems (sharp variation of elastic moduli with thin regions of > nearly incompressible material). I use snes_type newtonls, linesearch_type > cp, and pc_type gamg without any further options. pc_type Jacobi converges > fine (although slowly of course). > > > I am not really surprised that gamg would not converge out of the box, but > don’t know where to start to investigate the convergence failure. Can anybody > help? > > 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
