FluxML / FluxML/Tracker.jl

Issue with the gradient function

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Dominant language
Julia
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Description

I am working with Julia v1.6.7 and trying to execute this code:

W = rand(2, 5)
b = rand(2)
linear(x) = W * x .+ b
grads = gradient(() -> sum(linear(x)), Params([W, b]))

but I receive the error:

MethodError: no method matching back!(::Float64)
Closest candidates are:
back!(::Any, ::Any; once) at C:\Users\choud\.julia\packages\Tracker\tdXqL\src\back.jl:74
back!(::Tracker.TrackedReal; once) at C:\Users\choud\.julia\packages\Tracker\tdXqL\src\lib\real.jl:15
back!(::Tracker.TrackedArray) at C:\Users\choud\.julia\packages\Tracker\tdXqL\src\lib\array.jl:68

Stacktrace:
[1] gradient_(f::var"#96#97", xs::Tracker.Params)
@ Tracker C:\Users\choud\.julia\packages\Tracker\tdXqL\src\back.jl:4
[2] gradient_(f::Function, ps::Params{Zygote.Buffer{Array{Float64, N} where N, Vector{Array{Float64, N} where N}}})
@ Zygote.ZygoteTrackerExt C:\Users\choud\.julia\packages\Zygote\4SSHS\ext\ZygoteTrackerExt.jl:15
[3] #gradient#689
@ C:\Users\choud\.julia\packages\Tracker\tdXqL\src\back.jl:164 [inlined]
[4] gradient(f::Function, xs::Params{Zygote.Buffer{Array{Float64, N} where N, Vector{Array{Float64, N} where N}}})
@ Tracker C:\Users\choud\.julia\packages\Tracker\tdXqL\src\back.jl:164
[5] top-level scope
@ In[80]:4

Does this have to do anything with the version of my Julia

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Research direction

Reproduce the example with Julia v1.6.7, then start with the reported frames in Tracker/src/back.jl and ZygoteTrackerExt.jl, especially the back! calls. Compare the behavior with the supported Julia and dependency versions; done means identifying the compatibility or usage cause and documenting a confirmed resolution.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
machine-learning
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
30/100

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