Preserve Float type for Periodic Kernel (#560)

* 0.5d -> d/2 change for kappa function of periodic kernel

* test added

* strip trailing whitespace

* Update test/basekernels/periodic.jl

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>

---------

Co-authored-by: David Widmann <devmotion@users.noreply.github.com>
Co-authored-by: Will Tebbutt <wct23@cam.ac.uk>

Author: 3 people

Project.toml

@@ -1,6 +1,6 @@
 name = "KernelFunctions"
 uuid = "ec8451be-7e33-11e9-00cf-bbf324bd1392"
-version = "0.10.63"
+version = "0.10.64"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/basekernels/periodic.jl

@@ -34,7 +34,7 @@ PeriodicKernel(T::DataType, dims::Int=1) = PeriodicKernel(; r=ones(T, dims))
 
 metric(κ::PeriodicKernel) = Sinus(κ.r)
 
-kappa(::PeriodicKernel, d::Real) = exp(-0.5d)
+kappa(::PeriodicKernel, d::Real) = exp(-d / 2)
 
 function Base.show(io::IO, κ::PeriodicKernel)
     return print(io, "Periodic Kernel, length(r) = $(length(κ.r))")

test/basekernels/periodic.jl

@@ -8,6 +8,7 @@
     @test k(v1, v2) ≈ exp(-0.5 * sum(abs2, sinpi.(v1 - v2) ./ r))
     @test k(v1, v2) == k(v2, v1)
     @test PeriodicKernel(3)(v1, v2) == PeriodicKernel(; r=ones(3))(v1, v2)
+    @test PeriodicKernel(; r=Float32.(r))(Float32.(v1), Float32.(v2)) isa Float32
     @test repr(k) == "Periodic Kernel, length(r) = $(length(r))"
 
     # Standardised tests.