docs and test

Author: DominiqueMakowski

docs/src/index.md

@@ -18,6 +18,8 @@ logcosh
 logabssinh
 log1psq
 log1pexp
+softplus
+invsoftplus
 log1mexp
 log2mexp
 logexpm1

src/basicfuns.jl

@@ -272,6 +272,7 @@ See:
 """
 softplus(x::Real) = log1pexp(x)
 softplus(x::Real, a::Real) = log1pexp(a * x) / a
+softplus(x::Real; a::Real=1) = softplus(x, a)
 
 """
 $(SIGNATURES)
@@ -280,6 +281,7 @@ The inverse generalized `softplus` function (Wiemann et al., 2024). See [`softpl
 """
 invsoftplus(y::Real) = logexpm1(y)
 invsoftplus(y::Real, a::Real) = logexpm1(a * y) / a
+invsoftplus(y::Real; a::Real=1) = invsoftplus(y, a)
 
 
 """

test/basicfuns.jl

@@ -161,6 +161,16 @@ end
     end
 end
 
+@testset "softplus" begin
+    @test softplus(2) ≈ log1pexp(2)
+    @test softplus(2, 1) ≈ log1pexp(2)
+    @test softplus(2, a=1) ≈ log1pexp(2)
+    @test softplus(2, 10) < log1pexp(2)
+    @test invsoftplus(softplus(2), 1) ≈ 2
+    @test invsoftplus(softplus(2, 10), a=10) ≈ 2
+end
+
+
 @testset "log1mexp" begin
     for T in (Float64, Float32, Float16)
         @test @inferred(log1mexp(-T(1))) isa T