JuliaDiff / JuliaDiff/Diffractor.jl
Not using "strong zeros" for deriatives of constant values
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- Dominant language
- Julia
- Stars
- 453
- Forks
- 33
- PR merge metrics
- No merged PRs in 30d
Description
Compare:
julia> using Diffractor, Zygote
julia> var"'"(f) = Zygote.var"'"(f);
julia> exp'(Inf)
Inf
julia> exp''(Inf)
Inf
with
julia> var"'"(f) = Diffractor.PrimeDerivativeFwd(f);
julia> exp'(Inf)
Inf
julia> exp''(Inf)
NaN
You can see in the code_typed that it appears to be subtracting 0.0 * exp(x)^2 from the answer of 1.0 * exp(x), causing the NaN. Ideally this'd instead be 1.0 * exp(x) - ZeroTangent()*exp(x)^2 so that we don't get the NaN.
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
Start at Diffractor.PrimeDerivativeFwd and inspect the code_typed output for the exp derivatives shown in the Julia REPL examples. The issue is done when exp''(Inf) produces Inf rather than NaN, matching the Zygote comparison and preserving the strong-zero behavior described.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- julia
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100