Avoiding duplicate constraint/objective signature

[sshin23]

As @michel2323 pointed out, if the user writes the model in this way:

core = TwoStageExaCore()
  d =variable(core)
  v1 = variable(core, nv; scenario = 1)                                                                                                       
  v2 = variable(core, nv; scenario = 2)
  constraint(core, v1[j] + d for j in 1:nv; scenario = 1)
  constraint(core, v2[j] + d for j in 1:nv; scenario = 2)

The performance degrades because we will separately compile two constraint callbacks.

But maybe there are ways to get around this issue?

julia> typeof(core.con.f) == typeof(core.con.inner.f)
true
julia> typeof(core.con.itr) == typeof(core.con.inner.itr)
true

When we create a constraint, we can just check if we have a constraint of the same type and just augment the itr and recompute the offets, etc. if there is a known constraint type.

[sshin23]

Maybe in this way we can allow for loop over ExaModels, but maybe I'm too optimistic :)

[sshin23]

I think what we can do at least, is to issue a warning if it idenfies that same-looking constraint is already there

[michel2323]

Maybe we can use a boolean for scenario, or do we want to support heterogeneous scenarios? It makes no sense currently.

The two-stage tests are commented out. There are also still minor issues with it. Subexpressions are currently not picking up scenarios, for example.