Dear all, I am testing three multigrid preconditionners: BoomerAMG, ML and GAMG on a 3D elasticity problem (a cube with prescribed displacement on upper and lower faces). I set the null space by calling MatNullSpaceCreateRigidBody and then MatSetNearNullSpace).
I see a difference (about half iterations) for ML and GAMG but nothing happens with BoomerAMG (same number of iterations with and without setting the NearNullspace). Does it make sense ? Is this setting only relevant for Smoothed Aggregation AMG ? and of no use for BoomeAMG? Or do I miss something in the setting ? Thanks a lot, Best regards Natacha
