JuliaDiff / JuliaDiff/ForwardDiff.jl
method ambiguity in `ForwardDiff.derivative(x -> ℯ^x, 1/2)`
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- Dominant language
- Julia
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Description
It seems like a new method is needed to resolve this special case:
julia> ForwardDiff.derivative(x -> ℯ^x, 1/2)
ERROR: MethodError: ^(::Irrational{:ℯ}, ::ForwardDiff.Dual{ForwardDiff.Tag{var"#1#2",Float64},Float64,1}) is ambiguous. Candidates:
^(::Irrational{:ℯ}, x::Number) in Base.MathConstants at mathconstants.jl:91
^(x::Irrational, y::ForwardDiff.Dual{Ty,V,N} where N where V) where Ty in ForwardDiff at /Users/verzani/.julia/dev/ForwardDiff/src/dual.jl:140
Possible fix, define
^(::Irrational{:ℯ}, ::ForwardDiff.Dual{Ty,V,N} where N where V) where Ty
This is due to euler being special cased among the irrational values in mathconstants.jl
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Research direction
Reproduce the ambiguity with the ForwardDiff.derivative example, then inspect ForwardDiff/src/dual.jl around line 140 and Julia's mathconstants.jl around line 91. Compare the overlapping exponentiation methods and add focused coverage for the Irrational{:ℯ} and Dual combination; done means the example dispatches without MethodError and the relevant tests pass.
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Assessment
- Tech stack
- julia
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 45/100