Make scheduler options structs

[carstenbauer]

• For schedule=:static the reasonable default is nchunks=nthreads().
• For schedule=:dynamic the reasonable default is nchunks=x*nthreads(), where x is a small factor (maybe 2 or 3).
  • With the current default (nchunks=nthreads()) we have no load balancing and we're no better than @threads :dynamic.
• I haven't tested / thought about schedule=:greedy yet.

[carstenbauer]

See e.g. https://juliafolds2.github.io/OhMyThreads.jl/dev/examples/juliaset/juliaset/ for an example

[MasonProtter]

Yeah, I was thinking that with all of these different options and the way they depend on eachother, I'd want to make the schedule a struct. i.e. something like

Base.@kwdef struct GreedyScheduler
    nchunks::Int = nthreads()
    split::Symbol=:batch
end

[carstenbauer]

Might make sense, yes.