Merge pull request #1524 from BioTurboNick/number-zero-tangent

Prefer numeric zero over ZeroTangent for numeric arrays
FluxML · Sep 23, 2024 · 512184d · 512184d
2 parents f17ba75 + d4bf828
commit 512184d
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diff --git a/src/compiler/chainrules.jl b/src/compiler/chainrules.jl
@@ -162,6 +162,7 @@ end
 # For arrays, whitelist the safe ones, but always look inside Any[]:
 @inline wrap_chainrules_input(dxs::AbstractArray{<:Number}) = dxs
 @inline wrap_chainrules_input(dxs::AbstractArray{<:AbstractArray{<:Number}}) = dxs
+@inline wrap_chainrules_input(dxs::AbstractArray{<:Union{Nothing,T}}) where T <: Number = map(x -> x === nothing ? zero(T) : x, dxs)
 @inline wrap_chainrules_input(dxs::AbstractArray) = map(wrap_chainrules_input, dxs)
 
 #=

diff --git a/test/chainrules.jl b/test/chainrules.jl
@@ -420,3 +420,15 @@ end
  @test z2d_compiled.c.a === z2d_fallback.c.a
  @test z2d_compiled.c.b === z2d_fallback.c.b
 end
+
+@testset "ChainRules translation" begin
+ @test Zygote.wrap_chainrules_input(nothing) == ZeroTangent()
+ @test Zygote.wrap_chainrules_input((nothing,)) == ZeroTangent()
+ @test Zygote.wrap_chainrules_input([nothing]) == ZeroTangent()
+ @test Zygote.wrap_chainrules_input(((1.0, 2.0), 3.0)) == Tangent{Any}(Tangent{Any}(1.0, 2.0), 3.0)
+ @test Zygote.wrap_chainrules_input((; a = 1.0, b = 2.0)) == Tangent{Any}(a = 1.0, b = 2.0)
+ @test Zygote.wrap_chainrules_input(Ref(1)) == 1
+ @test Zygote.wrap_chainrules_input([2.0; 4.0]) == [2.0; 4.0]
+ @test Zygote.wrap_chainrules_input([[2.0; 4.0], [1.0; 3.0]]) == [[2.0; 4.0], [1.0; 3.0]]
+ @test Zygote.wrap_chainrules_input([nothing; 4.0]) == [0.0; 4.0] # ChainRules uses the numeric zero where possible
+end