JuliaDiff / JuliaDiff/ChainRulesCore.jl
ChainRulesCore.ProjectTo creates sparse matrices of the wrong element type (drops Duals)
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bug
help wanted
- Dominant language
- Julia
- Stars
- 267
- Forks
- 66
- PR merge metrics
- No merged PRs in 30d
Description
MWE:
using Zygote, SparseArrays, ForwardDiff
x, v = rand(Float32, 5), rand(Float32, 5)
A = sprand(Float32, 5, 5, 0.5)
loss(_x) = sum(tanh.(A * _x))
T = typeof(ForwardDiff.Tag(nothing, eltype(x)))
y = ForwardDiff.Dual{T, eltype(x), 1}.(x, ForwardDiff.Partials.(tuple.(reshape(v, size(x)))))
g = x -> first(Zygote.gradient(loss, x))
ForwardDiff.partials.(g(y), 1)
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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
Start by running the Julia MWE in the issue with Zygote, SparseArrays, and ForwardDiff, then trace the ChainRulesCore.ProjectTo path used for the sparse matrix. Confirm where the element type changes and verify that the completed fix preserves ForwardDiff.Dual values and their partials in the demonstrated case.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- julia
- Domain
- backend-api-design
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100