[petsc-users] Better PCGAMG Settings in 2D?

[Weston, Brian Thomas]

Hi Mark,

I’m using the default settings with GAMG for 2D problems and it’s performing much worse than BoomerAMG for my problem. I was told, however, that GAMG’s defaults were optimized for 3D problems, so I was wondering if you knew of better settings for 2D or which knobs might be most significant to play with? Is pc mg levels the way to control the number of aggressive coarsening levels? I tried using unsmoothed aggregation, but it was only marginally better than the default. 

The discretization is a essentially a 2nd-order cell-centered finite-volume scheme and I’m primarily solving a pressure-velocity Schur complement system.   

best,
Brian