compose tweaks

src/optimise/optimisers.jl

@@ -222,7 +222,7 @@ function update!(o::NADAM, x, Δ)
 end
 
 """
-   ADAMW((η = 0.001; β1 = 0.9, β2 = 0.999, ϵ = 1e-08, decay = 0)
+    ADAMW((η = 0.001; β1 = 0.9, β2 = 0.999, ϵ = 1e-08, decay = 0)
 
 [ADAMW](https://arxiv.org/abs/1711.05101) fixing weight decay regularization in Adam.
 """
@@ -231,36 +231,22 @@ ADAMW(η = 0.001, β = (0.9, 0.999), η_decay = 1, γ_decay = 0) = Compose(ADAM(
 # Compose optimizers
 
 """
-  `Compose(Compose(...), ...)`
+    Compose(a, b, c...)
 
-Compose optimizers to support inbuilt or custom gradient updates while fitting the loss.
-
-Example:\n\n
-`Compose(ADAM(), Compose(RMSProp(0.001), ExpDecay(0.02)))`
+Combine several optimisers into one; each optimiser produces a modified gradient
+that will be fed into the next, and this is finally applied to the parameter as
+usual.
 """
 mutable struct Compose
   os::Vector{Any}
+  Compose(o...) = new(Any[o...])
 end
 
-Compose(o...) = Compose(flattenCompose(o...))
-
 @forward Compose.os Base.getindex, Base.first, Base.last, Base.lastindex, Base.push!, Base.setindex!
 @forward Compose.os Base.iterate
 
 Base.getindex(c::Compose, i::AbstractArray) = Compose(c.os[i]...)
 
-function flattenCompose(o...)
-  res = []
-  for opt in o
-    if opt isa Compose
-      push!(res, flattenCompose(opt.os...)...)
-    else
-      push!(res, opt)
-    end
-  end
-  return res
-end
-
 function update!(o::Compose, x, Δ)
   for opt in o.os
     Δ = update!(opt, x, Δ)