Clarify LoadBalancer block pharein

[nicolasaunai]

Why

The current form of the LoadBalancer block is confusing. Some parameters (nppc/homogeneous, tol) apply to the whole hierarchy ,including L0, whereas others ones apply only the L0 rebalancing but users cannot know that from the block structure.

What

The LoadBalancer block ideal should reflect, from how it asks the user to set its parameters, what is general and what is L0 only.

Ideas on how (optional)

No response

Alternatives considered

No response

Additional context

No response

[PhilipDeegan]

https://github.com/llnl/SAMRAI/blob/817947517a69f33174dadd79bc7d1888c59ef2e3/source/SAMRAI/mesh/GriddingAlgorithm.cpp#L74-L75

samrai defaults the L0 LB to the general LB, so we have a way to have two LBs, L0 and everything else

[nicolasaunai]

but currently these params I mention only apply for L0 no?

[PhilipDeegan]

somethings only apply to L0 regardless, regridding of L1+ takes into account tolerance, but not much else

[nicolasaunai]

and are not obvious, I am always confused as to which param applies to where.

[PhilipDeegan]

my understanding is that only L0 is ever manually load balanced, when we actually trigger it, whereas regridding of higher levels automatically takes the nppc/tolerance into account