Add RADAM optimizer

NEWS.md

@@ -1,6 +1,7 @@
 # v0.9.0
 * [Depthwise convolutional layer API changes](https://github.com/FluxML/Flux.jl/pull/756) from `in => mult` channel specification to `in => out` channel specification, and deprecates implicit `out` constructor.
 * New [SkipConnection](https://github.com/FluxML/Flux.jl/pull/446), which can be used to train residual neural network architectures.
+* New [RADAM](https://github.com/FluxML/Flux.jl/pull/842) optimiser.
 
 # v0.8.0
 

src/Flux.jl

@@ -22,7 +22,7 @@ using .Optimise
 using .Optimise: @epochs
 export SGD, Descent, ADAM, Momentum, Nesterov, RMSProp,
   ADAGrad, AdaMax, ADADelta, AMSGrad, NADAM,
-  ADAMW, InvDecay, ExpDecay, WeightDecay
+  ADAMW, RADAM, InvDecay, ExpDecay, WeightDecay
 
 include("utils.jl")
 include("onehot.jl")

src/optimise/Optimise.jl

@@ -2,7 +2,7 @@ module Optimise
 
 export train!,
 	SGD, Descent, ADAM, Momentum, Nesterov, RMSProp,
-	ADAGrad, AdaMax, ADADelta, AMSGrad, NADAM, ADAMW,
+	ADAGrad, AdaMax, ADADelta, AMSGrad, NADAM, ADAMW,RADAM, 
 	InvDecay, ExpDecay, WeightDecay, stop, Optimiser
 
 include("optimisers.jl")

src/optimise/optimisers.jl

@@ -108,6 +108,36 @@ function apply!(o::ADAM, x, Δ)
   return Δ
 end
 
+"""
+    RADAM(η = 0.001, β = (0.9, 0.999))
+
+[RADAM](https://arxiv.org/pdf/1908.03265v1.pdf) optimiser (Rectified ADAM).
+"""
+mutable struct RADAM
+  eta::Float64
+  beta::Tuple{Float64,Float64}
+  state::IdDict
+end
+
+RADAM(η = 0.001, β = (0.9, 0.999)) = RADAM(η, β, IdDict())
+
+function apply!(o::RADAM, x, Δ)
+  η, β = o.eta, o.beta
+  ρ∞ = 2/(1-β[2])-1
+  mt, vt, βp, t = get!(o.state, x, (zero(x), zero(x), β, 1))
+  @. mt = β[1] * mt + (1 - β[1]) * Δ
+  @. vt = β[2] * vt + (1 - β[2]) * Δ^2
+  ρ = ρ∞ - 2t*βp[2]/(1-βp[2])
+  if ρ > 4
+    r = sqrt((ρ-4)*(ρ-2)*ρ∞/((ρ∞-4)*(ρ∞-2)*ρ))
+    @. Δ =  mt / (1 - βp[1]) / (√(vt / (1 - βp[2])) + ϵ) * η * r
+  else
+    @. Δ =  mt / (1 - βp[1]) * η
+  end
+  o.state[x] = (mt, vt, βp .* β, t+1)
+  return Δ
+end
+
 """
     AdaMax(params, η = 0.001; β1 = 0.9, β2 = 0.999, ϵ = 1e-08)
 

test/optimise.jl

@@ -5,7 +5,7 @@ using Test
 @testset "Optimise" begin
   w = randn(10, 10)
   @testset for opt in [ADAMW(), ADAGrad(0.1), AdaMax(), ADADelta(0.9), AMSGrad(),
-                       NADAM(), Descent(0.1), ADAM(), Nesterov(), RMSProp(),
+                       NADAM(), RADAM(), Descent(0.1), ADAM(), Nesterov(), RMSProp(),
                        Momentum()]
     w′ = param(randn(10, 10))
     loss(x) = Flux.mse(w*x, w′*x)