Changing Distances adjoints to ChainRules syntax

Project.toml

@@ -1,6 +1,6 @@
 name = "Zygote"
 uuid = "e88e6eb3-aa80-5325-afca-941959d7151f"
-version = "0.6.6"
+version = "0.6.7"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"

src/lib/distances.jl

@@ -1,22 +1,23 @@
 using .Distances
+import .ChainRules: NO_FIELDS, rrule
 
-@adjoint function (::SqEuclidean)(x::AbstractVector, y::AbstractVector)
+function rrule(::SqEuclidean, x::AbstractVector, y::AbstractVector)
   δ = x .- y
   function sqeuclidean(Δ::Real)
     x̄ = (2 * Δ) .* δ
-    return x̄, -x̄
+    return NO_FIELDS, x̄, -x̄
   end
   return sum(abs2, δ), sqeuclidean
 end
 
-@adjoint function colwise(s::SqEuclidean, x::AbstractMatrix, y::AbstractMatrix)
+function rrule(::typeof(colwise), s::SqEuclidean, x::AbstractMatrix, y::AbstractMatrix)
   return colwise(s, x, y), function (Δ::AbstractVector)
     x̄ = 2 .* Δ' .* (x .- y)
-    return nothing, x̄, -x̄
+    return NO_FIELDS, NO_FIELDS, x̄, -x̄
   end
 end
 
-@adjoint function pairwise(s::SqEuclidean, x::AbstractMatrix, y::AbstractMatrix; dims::Int=2)
+function rrule(::typeof(pairwise), s::SqEuclidean, x::AbstractMatrix, y::AbstractMatrix; dims::Int=2)
   if dims==1
     return pairwise(s, x, y; dims=1), ∇pairwise(s, transpose(x), transpose(y), transpose)
   else
@@ -28,10 +29,10 @@ end
   function(Δ)
     x̄ = 2 .* (x * Diagonal(vec(sum(Δ; dims=2))) .- y * transpose(Δ))
     ȳ = 2 .* (y * Diagonal(vec(sum(Δ; dims=1))) .- x * Δ)
-    return (nothing, f(x̄), f(ȳ))
+    return NO_FIELDS, NO_FIELDS, f(x̄), f(ȳ)
   end
 
-@adjoint function pairwise(s::SqEuclidean, x::AbstractMatrix; dims::Int=2)
+function rrule(::typeof(pairwise), s::SqEuclidean, x::AbstractMatrix; dims::Int=2)
   if dims==1
     return pairwise(s, x; dims=1), ∇pairwise(s, transpose(x), transpose)
   else
@@ -43,28 +44,28 @@ end
   function(Δ)
     d1 = Diagonal(vec(sum(Δ; dims=1)))
     d2 = Diagonal(vec(sum(Δ; dims=2)))
-    return (nothing, x * (2 .* (d1 .+ d2 .- Δ .- transpose(Δ))) |> f)
+    return NO_FIELDS, NO_FIELDS, x * (2 .* (d1 .+ d2 .- Δ .- transpose(Δ))) |> f
   end
 
-@adjoint function (::Euclidean)(x::AbstractVector, y::AbstractVector)
+function rrule(::Euclidean, x::AbstractVector, y::AbstractVector)
   D = x .- y
   δ = sqrt(sum(abs2, D))
   function euclidean(Δ::Real)
     x̄ = ifelse(iszero(δ), D, (Δ / δ) .* D)
-    return x̄, -x̄
+    return NO_FIELDS, x̄, -x̄
   end
   return δ, euclidean
 end
 
-@adjoint function colwise(s::Euclidean, x::AbstractMatrix, y::AbstractMatrix)
+function rrule(::typeof(colwise), s::Euclidean, x::AbstractMatrix, y::AbstractMatrix)
   d = colwise(s, x, y)
   return d, function (Δ::AbstractVector)
     x̄ = (Δ ./ max.(d, eps(eltype(d))))' .* (x .- y)
-    return nothing, x̄, -x̄
+    return NO_FIELDS, NO_FIELDS, x̄, -x̄
   end
 end
 
-@adjoint function pairwise(::Euclidean, X::AbstractMatrix, Y::AbstractMatrix; dims=2)
+function rrule(::typeof(pairwise), ::Euclidean, X::AbstractMatrix, Y::AbstractMatrix; dims=2)
 
   # Modify the forwards-pass slightly to ensure stability on the reverse.
   function _pairwise_euclidean(X, Y)
@@ -74,16 +75,16 @@ end
   D, back = pullback(_pairwise_euclidean, X, Y)
 
   return D, function(Δ)
-    return (nothing, back(Δ)...)
+    return (NO_FIELDS, NO_FIELDS, back(Δ)...)
   end
 end
 
-@adjoint function pairwise(::Euclidean, X::AbstractMatrix; dims=2)
+function rrule(::typeof(pairwise), ::Euclidean, X::AbstractMatrix; dims=2)
   D, back = pullback(X -> pairwise(SqEuclidean(), X; dims = dims), X)
   D .= sqrt.(D)
   return D, function(Δ)
     Δ = Δ ./ (2 .* max.(D, eps(eltype(D))))
     Δ[diagind(Δ)] .= 0
-    return (nothing, first(back(Δ)))
+    return (NO_FIELDS, NO_FIELDS, first(back(Δ)))
   end
 end