added SoftPlus

Author: nantonel

docs/src/operators.md

@@ -54,6 +54,7 @@ LBFGS
 
 ```@docs
 Sigmoid
+SoftPlus
 SoftMax
 ```
 

src/AbstractOperators.jl

@@ -62,6 +62,7 @@ include("calculus/NonLinearCompose.jl")
 # Non-Linear operators
 include("nonlinearoperators/Sigmoid.jl")
 include("nonlinearoperators/SoftMax.jl")
+include("nonlinearoperators/SoftPlus.jl")
 
 # Syntax
 include("syntax.jl")

src/nonlinearoperators/SoftPlus.jl

@@ -0,0 +1,37 @@
+export SoftPlus
+
+"""
+`SoftPlus([domainType=Float64::Type,] dim_in::Tuple)`
+
+Creates the softplus non-linear operator with input dimensions `dim_in`.
+```math
+\\sigma(\\mathbf{x}) = \\log (1 + e^{x} )
+```
+
+"""
+struct SoftPlus{T,N} <: NonLinearOperator
+	dim::NTuple{N,Int}
+end
+
+function SoftPlus(DomainType::Type, DomainDim::NTuple{N,Int}) where {N} 
+	SoftPlus{DomainType,N}(DomainDim)
+end
+
+SoftPlus(DomainDim::NTuple{N,Int}) where {N} = SoftPlus{Float64,N}(DomainDim)
+
+function A_mul_B!(y::AbstractArray{T,N}, L::SoftPlus{T,N}, x::AbstractArray{T,N}) where {T,N}
+	y .= log.(1.+exp.(x))
+end
+
+function Ac_mul_B!(y::AbstractArray{T,N}, 
+		   L::Jacobian{A}, 
+		   b::AbstractArray{T,N}) where {T,N, A <: SoftPlus{T,N}}
+	y .= 1./(1.+exp.(-L.x)).*b
+end
+
+fun_name(L::SoftPlus) = "σ"
+
+size(L::SoftPlus) = (L.dim, L.dim)
+
+domainType(L::SoftPlus{T,N}) where {T,N} = T
+codomainType(L::SoftPlus{T,N}) where {T,N} = T

test/test_nonlinear_operators.jl

@@ -28,3 +28,15 @@ r = randn(n,m,l)
 op = SoftMax(Float64,(n,m,l))
 
 y, grad = test_NLop(op,x,r,verb)
+
+n = 10
+x = randn(n)
+r = randn(n)
+op = SoftPlus(Float64,(n,))
+
+n,m,l = 4,5,6
+x = randn(n,m,l)
+r = randn(n,m,l)
+op = SoftPlus(Float64,(n,m,l))
+
+y, grad = test_NLop(op,x,r,verb)