Remove chainrule and test for SqMahalanobis (#539)

Author: simsurace

Project.toml

@@ -1,6 +1,6 @@
 name = "KernelFunctions"
 uuid = "ec8451be-7e33-11e9-00cf-bbf324bd1392"
-version = "0.10.59"
+version = "0.10.60"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/chainrules.jl

@@ -121,28 +121,6 @@ function ChainRulesCore.rrule(s::Sinus, x::AbstractVector, y::AbstractVector)
     return val, evaluate_pullback
 end
 
-## Reverse Rules SqMahalanobis
-
-function ChainRulesCore.rrule(
-    dist::Distances.SqMahalanobis, a::AbstractVector, b::AbstractVector
-)
-    d = dist(a, b)
-    function SqMahalanobis_pullback(Δ::Real)
-        a_b = a - b
-        ∂qmat = InplaceableThunk(
-            X̄ -> mul!(X̄, a_b, a_b', true, Δ), @thunk((a_b * a_b') * Δ)
-        )
-        ∂a = InplaceableThunk(
-            X̄ -> mul!(X̄, dist.qmat, a_b, true, 2 * Δ), @thunk((2 * Δ) * dist.qmat * a_b)
-        )
-        ∂b = InplaceableThunk(
-            X̄ -> mul!(X̄, dist.qmat, a_b, true, -2 * Δ), @thunk((-2 * Δ) * dist.qmat * a_b)
-        )
-        return Tangent{typeof(dist)}(; qmat=∂qmat), ∂a, ∂b
-    end
-    return d, SqMahalanobis_pullback
-end
-
 ## Reverse Rules for matrix wrappers
 
 function ChainRulesCore.rrule(::Type{<:ColVecs}, X::AbstractMatrix)

test/chainrules.jl

@@ -3,8 +3,6 @@
     x = rand(rng, 5)
     y = rand(rng, 5)
     r = rand(rng, 5)
-    Q = Matrix(Cholesky(rand(rng, 5, 5), 'U', 0))
-    @assert isposdef(Q)
 
     compare_gradient(:Zygote, [x, y]) do xy
         Euclidean()(xy[1], xy[2])
@@ -21,11 +19,4 @@
     compare_gradient(:Zygote, [x, y]) do xy
         KernelFunctions.Sinus(r)(xy[1], xy[2])
     end
-    if VERSION < v"1.6"
-        @test_broken "Chain rule of SqMahalanobis is broken in Julia pre-1.6"
-    else
-        compare_gradient(:Zygote, [Q, x, y]) do Qxy
-            SqMahalanobis(Qxy[1])(Qxy[2], Qxy[3])
-        end
-    end
 end