JuliaDiff / JuliaDiff/Diffractor.jl
Failing to compute Hessian via Jacobian of gradient
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Description
I am on 1.10.0-beta2 with environment:
Status ~/1.10/Project.toml
[c29ec348] AbstractDifferentiation v0.5.2
[9f5e2b26] Diffractor v0.2.1
[31c24e10] Distributions v0.25.100
[f6369f11] ForwardDiff v0.10.36
[276daf66] SpecialFunctions v2.3.1
[4c63d2b9] StatsFuns v1.3.0
Trying to compute Hessian with Diffractor.jl.
First, it would be nice if hessian from AbstractDifferentiation.jl would be supported for Diffractor.jl, like gradient and jacobian, but as far as I can see it is not yet.
Trying to get around this, I am computing the jacobian of the gradient to get the Hessian. But this fails even on a trivial function:
using Diffractor: DiffractorForwardBackend
using AbstractDifferentiation: gradient, jacobian, hessian
θ = [1.0,2.0]
∇(θ) = Diffractor.gradient(θ -> sum(θ.^2), θ)
∇(θ) # gradient works
# Hessian directly
hessian(DiffractorForwardBackend(), θ -> sum(θ.^2), θ) # not supported
# Hessian as jacobian of gradient
jacobian(DiffractorForwardBackend(), θ -> ∇(θ)[1], θ) # errors with error a bottom
f(θ) = 2*θ # coding up the gradient directly
jacobian(DiffractorForwardBackend(), θ -> f(θ), θ) # works, as expected
g(θ) = ∇(θ)[1]
jacobian(DiffractorForwardBackend(), θ -> g(θ), θ) # errors with error a bottom
ERROR: Unexprected statement encountered. This is a bug in Diffractor. stmt=$(Expr(:new_opaque_closure, Tuple{Any}, Union{}, Any, ∂⃖¹₁#3(...) @ Diffractor none:0, nothing, :(%6), :(%9), :(%12), :(%15), :(%18), nothing))
Stacktrace:
[1] error(s::String)
@ Base ./error.jl:35
[2] (::Diffractor.var"#mapstmt!#220"{Core.MethodInstance, Int64, Diffractor.var"#emit!#219"{Vector{Any}, Vector{Any}}, Vector{Int64}})(stmt::Any)
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/codegen/forward.jl:70
[3] fwd_transform!(ci::Core.CodeInfo, mi::Core.MethodInstance, nargs::Int64, N::Int64)
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/codegen/forward.jl:91
[4] fwd_transform(::Core.CodeInfo, ::Core.MethodInstance, ::Vararg{Any})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/codegen/forward.jl:3
[5] perform_fwd_transform(world::UInt64, source::LineNumberNode, ff::Type{Diffractor.∂☆recurse{1}}, args::Any)
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/recurse_fwd.jl:62
[6] ∂☆internal
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121 [inlined]
[7] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160 [inlined]
[8] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:254 [inlined]
[9] ∂⃖
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/generated.jl:215 [inlined]
[10] ∂☆internal
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121 [inlined]
[11] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160 [inlined]
[12] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:254 [inlined]
[13] ∂⃖
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/interface.jl:25 [inlined]
[14] ∂☆internal
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121 [inlined]
[15] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160 [inlined]
[16] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:254 [inlined]
[17] ∇
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/interface.jl:120 [inlined]
[18] (::Diffractor.∂☆recurse{1})(::ZeroBundle{1, Diffractor.∇{var"#3#4"}}, ::Diffractor.TangentBundle{1, Vector{Float64}, Diffractor.TaylorTangent{Tuple{Vector{Float64}}}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/recurse_fwd.jl:0
[19] (::Diffractor.∂☆internal{1})(::ZeroBundle{1, Diffractor.∇{var"#3#4"}}, ::Vararg{Diffractor.AbstractTangentBundle{1}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121
[20] (::Diffractor.∂☆{1})(::ZeroBundle{1, Diffractor.∇{var"#3#4"}}, ::Vararg{Diffractor.AbstractTangentBundle{1}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160
[21] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:254 [inlined]
[22] ∇
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/interface.jl:127 [inlined]
[23] (::Diffractor.∂☆recurse{1})(::ZeroBundle{1, Type{Diffractor.∇}}, ::ZeroBundle{1, var"#3#4"}, ::Diffractor.TangentBundle{1, Vector{Float64}, Diffractor.TaylorTangent{Tuple{Vector{Float64}}}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/recurse_fwd.jl:0
[24] (::Diffractor.∂☆internal{1})(::ZeroBundle{1, Type{Diffractor.∇}}, ::Vararg{Diffractor.AbstractTangentBundle{1}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121
[25] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160 [inlined]
[26] ∇
@ Diffractor ./REPL[8]:1 [inlined]
[27] ∂☆internal
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121 [inlined]
[28] ∂☆
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160 [inlined]
[29] #13
@ Diffractor ./REPL[16]:1 [inlined]
[30] (::Diffractor.∂☆recurse{1})(::ZeroBundle{1, var"#13#14"}, ::Diffractor.TangentBundle{1, Vector{Float64}, Diffractor.TaylorTangent{Tuple{Vector{Float64}}}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/recurse_fwd.jl:0
[31] (::Diffractor.∂☆internal{1})(::ZeroBundle{1, var"#13#14"}, ::Vararg{Diffractor.AbstractTangentBundle{1}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:121
[32] (::Diffractor.∂☆{1})(::ZeroBundle{1, var"#13#14"}, ::Vararg{Diffractor.AbstractTangentBundle{1}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/stage1/forward.jl:160
[33] (::Diffractor.var"#pushforward#359"{var"#13#14", Tuple{Vector{Float64}}})(vs::Tuple{Vector{Float64}})
@ Diffractor ~/.julia/packages/Diffractor/vzpvE/src/AbstractDifferentiation.jl:13
[34] (::Diffractor.var"#358#362")(cols::Any)
@ Diffractor ~/.julia/packages/AbstractDifferentiation/eEkWP/src/AbstractDifferentiation.jl:526 [inlined]
[35] mapslices(f::Diffractor.var"#358#362"{Diffractor.var"#pushforward#359"{var"#13#14", Tuple{Vector{Float64}}}}, A::Matrix{Float64}; dims::Int64)
@ Base ./abstractarray.jl:3179
[36] jacobian(b::DiffractorForwardBackend, f::Function, args::Vector{Float64})
@ Diffractor ~/.julia/packages/AbstractDifferentiation/eEkWP/src/AbstractDifferentiation.jl:524
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the minimal nested-Jacobian examples with the listed Julia and Diffractor versions. Start at src/codegen/forward.jl:70 and trace the AbstractDifferentiation.jl jacobian path shown in the stack trace. Done means the Jacobian of the Diffractor gradient no longer fails, with direct Hessian support considered separately.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- julia
- Domain
- machine-learning
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100