I can think of a few ways to implement the following multilevel scheme, but I'm not sure if it's possible/desirable to have DMMG to manage it.
Finest level (A) : DMComposite[DA_2D(dof=1),DA_3D(dof=4+)] Intermediate level (B) : DM_2D(dof=3) Coarsest levels (C1) : DM_2D(dof=1) OR (C2) : DM_2D(dof=3) No matrices are assembled on level A, but the smoother involves 1D solves within columns. Restriction A->B involves integration and discarding "slow" quantities. Assembly is available for Level B and higher matrices. There are two coarsening strategies after B, one involves a fieldsplit where the coarsest grids are only for a scalar problem, other coarsens B directly. I think grid sequencing and nonlinear multigrid are not important here because level B does not contain the long time scales for which globalization would be challenging. So this hierarchy is strictly for preconditioning. The DMMG interface is rather different from other components and I recall Barry saying he would like to eventually get rid of it. Is there an advantage to using it here? Unless I'm missing something, it would require some additions to the API (which I can do if it is the right thing to do). Jed
