# Flux v0.10.1 has no "tracked" array

**URL:** <https://discourse.julialang.org/t/flux-v0-10-1-has-no-tracked-array/35385>\
**Category:** New to Julia\
**Created:** [March 2, 2020, 5:23am UTC](https://discourse.julialang.org/t/flux-v0-10-1-has-no-tracked-array/35385 "2020-03-02T05:23:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Eldho.Ashna](https://avatars.discourse-cdn.com/v4/letter/e/bc8723/32.png) [@Eldho.Ashna](https://discourse.julialang.org/u/Eldho.Ashna)\
**Post date:** [March 2, 2020, 5:23am UTC](https://discourse.julialang.org/t/flux-v0-10-1-has-no-tracked-array/35385/1 "2020-03-02T05:23:10Z")

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Hi everyone.

I was learning Flux using the JUliaAcademy. Below is the link:

> **[Introduction to Flux](https://juliaacademy.com/courses/526449/lectures/9600470)**
>
> The definitive source for learning all things Julia, for free!

I’m facing the following problems while running this code:

1. model.W and model.b are not tracked ones.
2. Also, these weight and bias values are float 32 and not float 64.
3. When I type back!(loss), it is showing `UndefVarError: back! not defined`
4. When I type `?SGD`, it is showing:

```julia
search: SGD AMSGrad Signed signed Unsigned unsigned sigmoid issetgid logsigmoid

Couldn't find SGD
Perhaps you meant SGD, Set, Sys, BGR, GR, RGB, GC, spy, Some, sec, sin or sum

No documentation found.

Binding SGD does not exist.

```

I’m using Flux v0.10.1. I think it is the version problem. Can someone tell me how to sort this and make the code run for Flux v0.10.1.

Thanking you in advance.

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**Author:** ![carstenbauer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/carstenbauer/32/4981_2.png) [@carstenbauer](https://discourse.julialang.org/u/carstenbauer)\
**Post date:** [March 2, 2020, 6:13am UTC](https://discourse.julialang.org/t/flux-v0-10-1-has-no-tracked-array/35385/2 "2020-03-02T06:13:03Z")

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Most likely this course has been recorded before Flux v0.10.0. It was a very breaking release in which Flux started using a differnt AD, [Zygote.jl](https://github.com/FluxML/Zygote.jl), instead of Tracker. You could either try porting the examples or use an older version of Flux, for example `] add Flux@0.9.0`.