**BREAKING**: Move AD to package extensions and drop Zygote tests for Julia 1.12 and up

Project.toml

@@ -3,7 +3,6 @@ uuid = "ec8451be-7e33-11e9-00cf-bbf324bd1392"
 version = "0.11.0"
 
 [deps]
-ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"
 CompositionsBase = "a33af91c-f02d-484b-be07-31d278c5ca2b"
 Distances = "b4f34e82-e78d-54a5-968a-f98e89d6e8f7"
@@ -18,15 +17,18 @@ Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
 TensorCore = "62fd8b95-f654-4bbd-a8a5-9c27f68ccd50"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
-ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"
 
 [weakdeps]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 Kronecker = "2c470bb0-bcc8-11e8-3dad-c9649493f05e"
 PDMats = "90014a1f-27ba-587c-ab20-58faa44d9150"
+ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"
 
 [extensions]
+KernelFunctionsChainRulesCoreExt = "ChainRulesCore"
 KernelFunctionsKroneckerExt = "Kronecker"
 KernelFunctionsPDMatsExt = "PDMats"
+KernelFunctionsZygoteRulesExt = "ZygoteRules"
 
 [compat]
 ChainRulesCore = "1"

examples/train-kernel-parameters/script.jl

@@ -5,6 +5,10 @@
 
 # We load KernelFunctions and some other packages. Note that while we use `Zygote` for automatic differentiation and `Flux.optimise` for optimization, you should be able to replace them with your favourite autodiff framework or optimizer.
 
+# !!! note
+#     Zygote is not expected to work on Julia ≥ 1.12. Use a different AD package for
+#     Julia ≥ 1.12, or use Julia 1.11 to run this example.
+
 using KernelFunctions
 using LinearAlgebra
 using Distributions

src/chainrules.jl → ext/KernelFunctionsChainRulesCoreExt.jl

@@ -1,9 +1,18 @@
+module KernelFunctionsChainRulesCoreExt
+
+using ChainRulesCore:
+    ChainRulesCore, Tangent, ZeroTangent, NoTangent, @thunk, ProjectTo, unthunk
+using Distances: Distances, Euclidean, SqEuclidean
+using IrrationalConstants: twoπ
+using KernelFunctions: KernelFunctions, Delta, DotProduct, Sinus, ColVecs, RowVecs
+using LinearAlgebra: dot
+
 ## Forward Rules
 
 # Note that this is type piracy as the derivative should be NaN for x == y.
 function ChainRulesCore.frule(
     (_, Δx, Δy)::Tuple{<:Any,<:Any,<:Any},
-    d::Distances.Euclidean,
+    d::Euclidean,
     x::AbstractVector,
     y::AbstractVector,
 )
@@ -116,7 +125,7 @@ function ChainRulesCore.rrule(s::Sinus, x::AbstractVector, y::AbstractVector)
     gradx = π .* sinpi.(2 .* d) ./ s.r .^ 2
     function evaluate_pullback(Δ::Any)
         r̄ = -2Δ .* abs2_sind_r ./ s.r
-        s̄ = ChainRulesCore.Tangent{typeof(s)}(; r=r̄)
+        s̄ = Tangent{typeof(s)}(; r=r̄)
         return s̄, Δ * gradx, -Δ * gradx
     end
     return val, evaluate_pullback
@@ -150,7 +159,7 @@ function ChainRulesCore.rrule(
                 x̄[:, j] .-= ds
             end
         end
-        d̄ = ChainRulesCore.Tangent{typeof(d)}(; r=r̄)
+        d̄ = Tangent{typeof(d)}(; r=r̄)
         return NoTangent(), d̄, @thunk(project_x(x̄))
     end
     return Distances.pairwise(d, x; dims), pairwise_pullback
@@ -166,7 +175,7 @@ function ChainRulesCore.rrule(
         n = size(x, dims)
         m = size(y, dims)
         x̄ = collect(zero(x))
-        ȳ = collect(zero(y))
+        ȳ = collect(zero(y))
         r̄ = zero(d.r)
         if dims == 1
             for j in 1:m, i in 1:n
@@ -175,7 +184,7 @@ function ChainRulesCore.rrule(
                 ds = π .* Δ[i, j] .* sinpi.(2 .* (xi .- yj)) ./ d.r .^ 2
                 r̄ .-= 2 .* Δ[i, j] .* sinpi.(xi .- yj) .^ 2 ./ d.r .^ 3
                 x̄[i, :] .+= ds
-                ȳ[j, :] .-= ds
+                ȳ[j, :] .-= ds
             end
         elseif dims == 2
             for j in 1:m, i in 1:n
@@ -184,11 +193,11 @@ function ChainRulesCore.rrule(
                 ds = π .* Δ[i, j] .* sinpi.(2 .* (xi .- yj)) ./ d.r .^ 2
                 r̄ .-= 2 .* Δ[i, j] .* sinpi.(xi .- yj) .^ 2 ./ d.r .^ 3
                 x̄[:, i] .+= ds
-                ȳ[:, j] .-= ds
+                ȳ[:, j] .-= ds
             end
         end
-        d̄ = ChainRulesCore.Tangent{typeof(d)}(; r=r̄)
-        return NoTangent(), d̄, @thunk(project_x(x̄)), @thunk(project_y(ȳ))
+        d̄ = Tangent{typeof(d)}(; r=r̄)
+        return NoTangent(), d̄, @thunk(project_x(x̄)), @thunk(project_y(ȳ))
     end
     return Distances.pairwise(d, x, y; dims), pairwise_pullback
 end
@@ -202,18 +211,18 @@ function ChainRulesCore.rrule(
         Δ = unthunk(z̄)
         n = size(x, 2)
         x̄ = collect(zero(x))
-        ȳ = collect(zero(y))
+        ȳ = collect(zero(y))
         r̄ = zero(d.r)
         for i in 1:n
             xi = view(x, :, i)
             yi = view(y, :, i)
             ds = π .* Δ[i] .* sinpi.(2 .* (xi .- yi)) ./ d.r .^ 2
             r̄ .-= 2 .* Δ[i] .* sinpi.(xi .- yi) .^ 2 ./ d.r .^ 3
             x̄[:, i] .+= ds
-            ȳ[:, i] .-= ds
+            ȳ[:, i] .-= ds
         end
-        d̄ = ChainRulesCore.Tangent{typeof(d)}(; r=r̄)
-        return NoTangent(), d̄, @thunk(project_x(x̄)), @thunk(project_y(ȳ))
+        d̄ = Tangent{typeof(d)}(; r=r̄)
+        return NoTangent(), d̄, @thunk(project_x(x̄)), @thunk(project_y(ȳ))
     end
     return Distances.colwise(d, x, y), colwise_pullback
 end
@@ -247,3 +256,5 @@ function ChainRulesCore.rrule(::Type{<:RowVecs}, X::AbstractMatrix)
     end
     return RowVecs(X), RowVecs_pullback
 end
+
+end

src/zygoterules.jl → ext/KernelFunctionsZygoteRulesExt.jl

@@ -1,3 +1,8 @@
+module KernelFunctionsZygoteRulesExt
+
+using KernelFunctions: KernelFunctions, Transform, ColVecs, RowVecs, _map
+using ZygoteRules: ZygoteRules, AContext, literal_getproperty, literal_getfield
+
 ZygoteRules.@adjoint function Base.map(t::Transform, X::ColVecs)
     return ZygoteRules.pullback(_map, t, X)
 end
@@ -11,3 +16,5 @@ function ZygoteRules._pullback(
 ) where {f}
     return ZygoteRules._pullback(cx, literal_getfield, x, Val{f}())
 end
+
+end

src/KernelFunctions.jl

@@ -50,8 +50,6 @@ export IndependentMOKernel,
 export tensor, ⊗, compose
 
 using Compat
-using ChainRulesCore: ChainRulesCore, Tangent, ZeroTangent, NoTangent
-using ChainRulesCore: @thunk, InplaceableThunk, ProjectTo, unthunk
 using CompositionsBase
 using Distances
 using FillArrays
@@ -62,7 +60,6 @@ using IrrationalConstants: logtwo, twoπ, invsqrt2
 using LogExpFunctions: softplus
 using StatsBase
 using TensorCore
-using ZygoteRules: ZygoteRules, AContext, literal_getproperty, literal_getfield
 
 # Hack to work around Zygote type inference problems.
 const Distances_pairwise = Distances.pairwise
@@ -123,9 +120,6 @@ include("mokernels/slfm.jl")
 include("mokernels/intrinsiccoregion.jl")
 include("mokernels/lmm.jl")
 
-include("chainrules.jl")
-include("zygoterules.jl")
-
 include("TestUtils.jl")
 
 # Kronecker extension stubs

test/basekernels/fbm.jl

@@ -17,10 +17,12 @@
 
     # Tests failing for ForwardDiff and Zygote@0.6.
     # Related to: https://github.com/FluxML/Zygote.jl/issues/1036
-    f(x, y) = x^y
-    @test_broken !isinf(
-        Zygote.gradient((x, y) -> sum(f.(x, y)), zeros(1), fill(0.9, 1))[1][1]
-    )
+    if _TEST_ZYGOTE
+        f(x, y) = x^y
+        @test_broken !isinf(
+            Zygote.gradient((x, y) -> sum(f.(x, y)), zeros(1), fill(0.9, 1))[1][1]
+        )
+    end
 
     test_params(k, ([h],))
 

test/chainrules.jl

@@ -4,20 +4,24 @@
     y = rand(rng, 5)
     r = rand(rng, 5)
 
-    compare_gradient(:Zygote, [x, y]) do xy
-        Euclidean()(xy[1], xy[2])
-    end
-    compare_gradient(:Zygote, [x, y]) do xy
-        SqEuclidean()(xy[1], xy[2])
-    end
-    compare_gradient(:Zygote, [x, y]) do xy
-        KernelFunctions.DotProduct()(xy[1], xy[2])
-    end
-    compare_gradient(:Zygote, [x, y]) do xy
-        KernelFunctions.Delta()(xy[1], xy[2])
-    end
-    compare_gradient(:Zygote, [x, y]) do xy
-        KernelFunctions.Sinus(r)(xy[1], xy[2])
+    if _TEST_ZYGOTE
+        compare_gradient(:Zygote, [x, y]) do xy
+            Euclidean()(xy[1], xy[2])
+        end
+        compare_gradient(:Zygote, [x, y]) do xy
+            SqEuclidean()(xy[1], xy[2])
+        end
+        compare_gradient(:Zygote, [x, y]) do xy
+            KernelFunctions.DotProduct()(xy[1], xy[2])
+        end
+        compare_gradient(:Zygote, [x, y]) do xy
+            KernelFunctions.Delta()(xy[1], xy[2])
+        end
+        compare_gradient(:Zygote, [x, y]) do xy
+            KernelFunctions.Sinus(r)(xy[1], xy[2])
+        end
+    else
+        @test_broken false  # Zygote not supported on Julia >= 1.12
     end
     @testset "rrules for Sinus(r=$r)" for r in (rand(3),)
         dist = KernelFunctions.Sinus(r)

test/kernels/transformedkernel.jl

@@ -36,26 +36,30 @@
 
     # Test implicit gradients
     @testset "Implicit gradients" begin
-        k = SqExponentialKernel() ∘ ScaleTransform(2.0)
-        ps = params(k)
-        X = rand(10, 1)
-        x = vec(X)
-        A = rand(10, 10)
-        # Implicit
-        g1 = Zygote.gradient(ps) do
-            tr(kernelmatrix(k, X; obsdim=1) * A)
-        end
-        # Explicit
-        g2 = Zygote.gradient(k) do k
-            tr(kernelmatrix(k, X; obsdim=1) * A)
-        end
+        if _TEST_ZYGOTE
+            k = SqExponentialKernel() ∘ ScaleTransform(2.0)
+            ps = params(k)
+            X = rand(10, 1)
+            x = vec(X)
+            A = rand(10, 10)
+            # Implicit
+            g1 = Zygote.gradient(ps) do
+                tr(kernelmatrix(k, X; obsdim=1) * A)
+            end
+            # Explicit
+            g2 = Zygote.gradient(k) do k
+                tr(kernelmatrix(k, X; obsdim=1) * A)
+            end
 
-        # Implicit for a vector
-        g3 = Zygote.gradient(ps) do
-            tr(kernelmatrix(k, x) * A)
+            # Implicit for a vector
+            g3 = Zygote.gradient(ps) do
+                tr(kernelmatrix(k, x) * A)
+            end
+            @test g1[first(ps)] ≈ first(g2).transform.s
+            @test g1[first(ps)] ≈ g3[first(ps)]
+        else
+            @test_broken false  # Zygote not supported on Julia >= 1.12
         end
-        @test g1[first(ps)] ≈ first(g2).transform.s
-        @test g1[first(ps)] ≈ g3[first(ps)]
     end
 
     @testset "Parameters" begin

test/test_utils.jl

@@ -31,6 +31,8 @@ end
 
 # AD utilities
 
+const _TEST_ZYGOTE = VERSION < v"1.12"
+
 # Type to work around some performance issues that can happen on the reverse-pass of Zygote.
 # This context doesn't allow any globals. Don't use this if you use globals in your
 # programme.
@@ -42,6 +44,9 @@ Zygote.accum_param(::NoContext, x, Δ) = Δ
 
 const FDM = FiniteDifferences.central_fdm(5, 1)
 
+const _DEFAULT_ADS =
+    _TEST_ZYGOTE ? [:Zygote, :ForwardDiff, :ReverseDiff] : [:ForwardDiff, :ReverseDiff]
+
 gradient(f, s::Symbol, args) = gradient(f, Val(s), args)
 
 function gradient(f, ::Val{:Zygote}, args)
@@ -90,7 +95,7 @@ testdiagfunction(k::MOKernel, A) = sum(kernelmatrix_diag(k, A))
 testdiagfunction(k::MOKernel, A, B) = sum(kernelmatrix_diag(k, A, B))
 
 function test_ADs(
-    kernelfunction, args=nothing; ADs=[:Zygote, :ForwardDiff, :ReverseDiff], dims=[3, 3]
+    kernelfunction, args=nothing; ADs=_DEFAULT_ADS, dims=[3, 3]
 )
     test_fd = test_AD(:FiniteDiff, kernelfunction, args, dims)
     if !test_fd.anynonpass
@@ -101,14 +106,18 @@ function test_ADs(
 end
 
 function check_zygote_type_stability(f, args...; ctx=Zygote.Context())
+    if !_TEST_ZYGOTE
+        @test_broken false
+        return nothing
+    end
     @inferred f(args...)
     @inferred Zygote._pullback(ctx, f, args...)
     out, pb = Zygote._pullback(ctx, f, args...)
     @inferred collect(pb(out))
 end
 
 function test_ADs(
-    k::MOKernel; ADs=[:Zygote, :ForwardDiff, :ReverseDiff], dims=(in=3, out=2, obs=3)
+    k::MOKernel; ADs=_DEFAULT_ADS, dims=(in=3, out=2, obs=3)
 )
     test_fd = test_FiniteDiff(k, dims)
     if !test_fd.anynonpass
@@ -372,6 +381,10 @@ function test_zygote_perf_heuristic(
     f, name::String, args1, args2, passes, Δ1=nothing, Δ2=nothing
 )
     @testset "$name" begin
+        if !_TEST_ZYGOTE
+            @test_broken false
+            return nothing
+        end
         primal, fwd, pb = ad_constant_allocs_heuristic(f, args1, args2; Δ1, Δ2)
         if passes[1]
             @test primal[1] == primal[2]

test/transform/selecttransform.jl

@@ -103,7 +103,7 @@
         @test gx ≈ ga
     end
 
-    @testset "$(AD)" for AD in [:ReverseDiff, :Zygote]
+    @testset "$(AD)" for AD in (_TEST_ZYGOTE ? [:ReverseDiff, :Zygote] : [:ReverseDiff])
         @test_broken let
             gx = gradient(AD, X) do x
                 testfunction(tx_row, x, 2)