From b298b8a265b9f3767f4a8b9ab7b71aad0c2789f7 Mon Sep 17 00:00:00 2001
From: Eliott Van Dieren <vandieren.eliott@gmail.com>
Date: Mon, 13 Oct 2025 10:21:20 +0200
Subject: [PATCH 1/2] Adding Matern72Kernel object, tests and docs

---
 docs/src/kernels.md        |  1 +
 src/KernelFunctions.jl     |  2 +-
 src/basekernels/matern.jl  | 35 ++++++++++++++++++++++++++++++++++-
 test/basekernels/matern.jl | 25 +++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/docs/src/kernels.md b/docs/src/kernels.md
index 8f19091c6..6e91d20f7 100644
--- a/docs/src/kernels.md
+++ b/docs/src/kernels.md
@@ -61,6 +61,7 @@ MaternKernel
 Matern12Kernel
 Matern32Kernel
 Matern52Kernel
+Matern72Kernel
 ```
 
 ### Neural Network Kernel
diff --git a/src/KernelFunctions.jl b/src/KernelFunctions.jl
index 80711b4ec..8d5679d9a 100644
--- a/src/KernelFunctions.jl
+++ b/src/KernelFunctions.jl
@@ -10,7 +10,7 @@ export SqExponentialKernel, RBFKernel, GaussianKernel, SEKernel
 export LaplacianKernel, ExponentialKernel, GammaExponentialKernel
 export ExponentiatedKernel
 export FBMKernel
-export MaternKernel, Matern12Kernel, Matern32Kernel, Matern52Kernel
+export MaternKernel, Matern12Kernel, Matern32Kernel, Matern52Kernel, Matern72Kernel
 export LinearKernel, PolynomialKernel
 export RationalKernel, RationalQuadraticKernel, GammaRationalKernel
 export PiecewisePolynomialKernel
diff --git a/src/basekernels/matern.jl b/src/basekernels/matern.jl
index c009bf596..f0bb5a718 100644
--- a/src/basekernels/matern.jl
+++ b/src/basekernels/matern.jl
@@ -21,7 +21,7 @@ differentiable in the mean-square sense.
 
     Differentiation with respect to the order ν is not currently supported.
 
-See also: [`Matern12Kernel`](@ref), [`Matern32Kernel`](@ref), [`Matern52Kernel`](@ref)
+See also: [`Matern12Kernel`](@ref), [`Matern32Kernel`](@ref), [`Matern52Kernel`](@ref), [`Matern72Kernel`](@ref)
 """
 struct MaternKernel{Tν<:Real,M} <: SimpleKernel
     ν::Vector{Tν}
@@ -118,3 +118,36 @@ metric(k::Matern52Kernel) = k.metric
 function Base.show(io::IO, k::Matern52Kernel)
     return print(io, "Matern 5/2 Kernel (metric = ", k.metric, ")")
 end
+
+"""
+    Matern72Kernel(; metric=Euclidean())
+
+Matérn kernel of order ``7/2`` with respect to the `metric`.
+
+# Definition
+
+For inputs ``x, x'`` and metric ``d(\\cdot, \\cdot)``, the Matérn kernel of order ``7/2`` is
+given by
+```math
+k(x, x') = \\bigg(1 + \\sqrt{7} d(x, x') + \\frac{14}{5} d(x, x')^2 + 
+           \\frac{7\\sqrt{7}}{15} d(x, x')^3\\bigg)\\exp\\big(- \\sqrt{7} d(x, x') \\big).
+```
+By default, ``d`` is the Euclidean metric ``d(x, x') = \\|x - x'\\|_2``.
+
+See also: [`MaternKernel`](@ref)
+"""
+struct Matern72Kernel{M} <: SimpleKernel
+    metric::M
+end
+
+Matern72Kernel(; metric=Euclidean()) = Matern72Kernel(metric)
+
+function kappa(::Matern72Kernel, d::Real)
+    return (1 + sqrt(7) * d + 14 / 5 * d^2 + 7 * sqrt(7) / 15 * d^3) * exp(-sqrt(7) * d)
+end
+
+metric(k::Matern72Kernel) = k.metric
+
+function Base.show(io::IO, k::Matern72Kernel)
+    return print(io, "Matern 7/2 Kernel (metric = ", k.metric, ")")
+end
diff --git a/test/basekernels/matern.jl b/test/basekernels/matern.jl
index e0be7054d..2167b0d9d 100644
--- a/test/basekernels/matern.jl
+++ b/test/basekernels/matern.jl
@@ -82,9 +82,34 @@
         test_ADs(Matern52Kernel)
         test_interface_ad_perf(_ -> Matern52Kernel(), nothing, StableRNG(123456))
     end
+    @testset "Matern72Kernel" begin
+        k = Matern72Kernel()
+        @test kappa(k, x) ≈
+            (1 + sqrt(7) * x + 14 / 5 * x^2 + 7 * sqrt(7) / 15 * x^3) * exp(-sqrt(7) * x)
+        @test k(v1, v2) ≈
+            (
+            1 +
+            sqrt(7) * norm(v1 - v2) +
+            14 / 5 * norm(v1 - v2)^2 +
+            7 * sqrt(7) / 15 * norm(v1 - v2)^3
+        ) * exp(-sqrt(7) * norm(v1 - v2))
+        @test kappa(Matern72Kernel(), x) == kappa(k, x)
+        @test metric(Matern72Kernel()) == Euclidean()
+        @test repr(k) == "Matern 7/2 Kernel (metric = Euclidean(0.0))"
+
+        k2 = Matern72Kernel(; metric=WeightedEuclidean(ones(3)))
+        @test metric(k2) isa WeightedEuclidean
+        @test k2(v1, v2) ≈ k(v1, v2)
+
+        # Standardised tests.
+        TestUtils.test_interface(k, Float64)
+        test_ADs(Matern72Kernel)
+        test_interface_ad_perf(_ -> Matern72Kernel(), nothing, StableRNG(123456))
+    end
     @testset "Coherence Materns" begin
         @test kappa(MaternKernel(; ν=0.5), x) ≈ kappa(ExponentialKernel(), x)
         @test kappa(MaternKernel(; ν=1.5), x) ≈ kappa(Matern32Kernel(), x)
         @test kappa(MaternKernel(; ν=2.5), x) ≈ kappa(Matern52Kernel(), x)
+        @test kappa(MaternKernel(; ν=3.5), x) ≈ kappa(Matern72Kernel(), x)
     end
 end

From 56883368eb7ca8efb56a0a4839f219c63ac2097c Mon Sep 17 00:00:00 2001
From: Eliott Van Dieren <vandieren.eliott@gmail.com>
Date: Tue, 14 Oct 2025 09:05:52 +0200
Subject: [PATCH 2/2] Bump patch version

---
 Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 2b5d92709..71f9bf182 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "KernelFunctions"
 uuid = "ec8451be-7e33-11e9-00cf-bbf324bd1392"
-version = "0.10.65"
+version = "0.10.66"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"