GMG:clear out mg constraints [WIP]

[zjiaqi2018]

1. Remove user_level_constraints and level_constraints and use mg_level_constraints to store boundary constraints on all levels.
2. Use level_boundary_indices to store zero boundary constraints, and then add to mg_level_constraints.
3. A new function to import mg_level_constraints to mg_constrained_dofs.

[zjiaqi2018]

deal.ii 9.3 doesn't have the following function mg_constrained_dofs.add_boundary_indices()

[tjhei]

Can you try https://github.com/geodynamics/aspect/pull/4413/commits/fa3b677fe03f5e42029690ba16bd36e2dce9471c or something similar for <9.5? I am curious if any tests are affected.

[zjiaqi2018]

Can you try fa3b677 or something similar for <9.5? I am curious if any tests are affected.

So you want to clear the level constraints before adding new ones?

[tjhei]

So you want to clear the level constraints before adding new ones?

Ideally, we would only clear out the user constraints, but the next best thing (as this is not available unless we use master) would be to clear and redo all constraints. Does that makes sense?

[bangerth]

@tjhei What do we do about this PR from last year?

[tjhei]

Will look at it again this hackathon

[gassmoeller]

@tjhei: What about this hackathon? ;-)