JuliaDiff / JuliaDiff/ForwardDiff.jl
ForwardDiff.jacobian does not respect Array dimensionality
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Description
f(x) = sum(x; dims=1)
ForwardDiff.jacobian(f, [1. 2.; 3. 4.]) # returns 2x4 Array
Shouldn't it return a 1x2x2x2 Array?
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- 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 reproducing the ForwardDiff.jacobian example with f(x) = sum(x; dims=1) and the 2×2 input shown in the issue. Trace how jacobian handles the dimensionality of the returned array; done means the result preserves the expected 1×2×2×2 shape rather than returning a 2×4 Array.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- julia
- Domain
- data
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100