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fix(zygote ext): return struct-tangent cotangent from Array(::AbstractVectorOfArray) #587

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fix(zygote ext): return struct-tangent cotangent from Array(::AbstractVectorOfArray) #587

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18 changes: 13 additions & 5 deletions ext/RecursiveArrayToolsZygoteExt.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,8 @@ end
# using linear indexing (which now returns scalar elements for VectorOfArray).
if y isa AbstractVectorOfArray
(y.u,)
elseif y isa NamedTuple && haskey(y, :u)
(y.u,)
else
(
[
Expand All @@ -68,6 +70,8 @@ end
end
if y isa AbstractVectorOfArray
(y.u, nothing)
elseif y isa NamedTuple && haskey(y, :u)
(y.u, nothing)
else
(
[
Expand Down Expand Up @@ -113,11 +117,15 @@ end

@adjoint function Base.Array(VA::AbstractVectorOfArray)
adj = let VA = VA
function Array_adjoint(y)
# Return a VectorOfArray so it flows correctly back through VectorOfArray constructor
VA = recursivecopy(VA)
copyto!(VA, y)
return (VA,)
function Array_adjoint(y::AbstractArray{T, N}) where {T, N}
arrarr = [
[
y[ntuple(_ -> Colon(), Val(N - 2))..., j, i]
for j in 1:size(y)[end - 1]
]
for i in 1:size(y)[end]
]
return ((u = arrarr,),)
end
end
Array(VA), adj
Expand Down
42 changes: 42 additions & 0 deletions test/adjoints.jl
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Expand Up @@ -90,3 +90,45 @@ voa_gs, = Zygote.gradient(voa) do x
sum(sum.(x.u))
end
@test voa_gs isa RecursiveArrayTools.VectorOfArray

@testset "Base.Array(::AbstractVectorOfArray) cotangent shape" begin
let voa = VectorOfArray([Float64.(1:3), Float64.(4:6), Float64.(7:9)])
y = Array(voa)
@test size(y) == (3, 3)
_, back = Zygote.pullback(Base.Array, voa)
cot, = back(ones(Float64, size(y)))
@test cot isa NamedTuple
@test haskey(cot, :u)
@test length(cot.u) == length(voa.u)
for i in eachindex(voa.u)
@test cot.u[i] == ones(Float64, length(voa.u[i]))
end
end

let ntraj = 4, ntime = 5, nstate = 2
voa = VectorOfArray([
VectorOfArray([Float64.((j - 1) * nstate .+ (1:nstate)) .+ (i - 0.5)
for j in 1:ntime])
for i in 1:ntraj
])
y = Array(voa)
@test size(y) == (nstate, ntime, ntraj)
_, back = Zygote.pullback(Base.Array, voa)
cot, = back(reshape(collect(Float64, 1:length(y)), size(y)))
@test cot isa NamedTuple
@test length(cot.u) == ntraj
for i in 1:ntraj
@test length(cot.u[i]) == ntime
@test all(length(v) == nstate for v in cot.u[i])
end
end
end

@testset "Array(::VectorOfArray) gradient matches ForwardDiff" begin
function row_loss(x)
voa = VectorOfArray([x .* i for i in 1:5])
sum(abs2, 1.0 .- Array(voa))
end
x = collect(Float64, 1:5)
@test Zygote.gradient(row_loss, x)[1] == ForwardDiff.gradient(row_loss, x)
end
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