# Compute gradient of gradient norm using zygote

**URL:** <https://discourse.julialang.org/t/compute-gradient-of-gradient-norm-using-zygote/79712>\
**Category:** New to Julia\
**Tags:** zygote\
**Created:** [April 19, 2022, 11:04pm UTC](https://discourse.julialang.org/t/compute-gradient-of-gradient-norm-using-zygote/79712 "2022-04-19T23:04:22Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Post date:** [April 20, 2022, 5:22am UTC](https://discourse.julialang.org/t/compute-gradient-of-gradient-norm-using-zygote/79712/2 "2022-04-20T05:22:36Z")

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Hi and welcome to the community!  
Could you post a minimal working example so that it is easier to help you?

> [@Please read: make it easier to help you](https://discourse.julialang.org/t/please-read-make-it-easier-to-help-you/14757):
>
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At first glance, it seems the problem comes from nested derivatives with Zygote: maybe this link can help

> <https://github.com/FluxML/Zygote.jl/issues/33>
>
> \`\`\`julia
> julia\> derivative(x-\>x\*derivative(y-\>x+y,1),1)
> ERROR: MethodError: no… method matching exprtype(::Core.Compiler.IRCode, ::String)
> Closest candidates are:
> exprtype(::Core.Compiler.IRCode, ::Expr) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\tools\\ir.jl:54
> exprtype(::Core.Compiler.IRCode, ::QuoteNode) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\tools\\ir.jl:51
> exprtype(::Core.Compiler.IRCode, ::GlobalRef) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\tools\\ir.jl:50
> ...
> Stacktrace:
> \[1\] \_broadcast\_getindex\_evalf at .\\broadcast.jl:574 \[inlined\]
> \[2\] \_broadcast\_getindex at .\\broadcast.jl:547 \[inlined\]
> \[3\] getindex at .\\broadcast.jl:507 \[inlined\]
> \[4\] copyto\_nonleaf!(::Array{DataType,1}, ::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1},Tuple{Base.OneTo{Int64}},typeof(Zygote.exprtype),Tuple{Base.RefValue{Core.Compiler.IRCode},Base.Broadcast.Extruded{Array{Any,1},Tuple{Bool},Tuple{Int64}}}}, ::Base.OneTo{Int64}, ::Int64, ::Int64) at .\\broadcast.jl:923
> \[5\] copy(::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1},Tuple{Base.OneTo{Int64}},typeof(Zygote.exprtype),Tuple{Base.RefValue{Core.Compiler.IRCode},Array{Any,1}}}) at .\\broadcast.jl:786
> \[6\] materialize(::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1},Nothing,typeof(Zygote.exprtype),Tuple{Base.RefValue{Core.Compiler.IRCode},Array{Any,1}}}) at .\\broadcast.jl:748
> \[7\] record!(::Core.Compiler.IRCode) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\reverse.jl:144
> \[8\] #Primal#39(::Int64, ::Type, ::Core.Compiler.IRCode) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\reverse.jl:189
> \[9\] Type at .\\none:0 \[inlined\]
> \[10\] #Adjoint#65 at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\reverse.jl:387 \[inlined\]
> \[11\] (::getfield(Core, Symbol("#kw#Type")))(::NamedTuple{(:varargs,),Tuple{Int64}}, ::Type{Zygote.Adjoint}, ::Core.Compiler.IRCode) at .\\none:0
> \[12\] \_lookup\_grad(::Type) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\emit.jl:121
> \[13\] #s18#633 at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface2.jl:17 \[inlined\]
> \[14\] #s18#633(::Any, ::Any, ::Any) at .\\none:0
> \[15\] (::Core.GeneratedFunctionStub)(::Any, ::Vararg{Any,N} where N) at .\\boot.jl:506
> \[16\] derivative at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface.jl:37 \[inlined\]
> \[17\] (::Zygote.J{Tuple{typeof(derivative),getfield(Main, Symbol("##32#34")){Int64},Int64},Tuple{typeof(derivative),getfield(Main, Symbol("##32#34")){Int64},Int64,getfield(Zygote, Symbol("##148#back2#115")){getfield(Zygote, Symbol("##111#113")){1,Int64}},Zygote.J{Tuple{typeof(gradient),getfield(Main, Symbol("##32#34")){Int64},Int64},Tuple{typeof(gradient)}}}})(::Int64) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface2.jl:0
> \[18\] #31 at .\\REPL\[11\]:1 \[inlined\]
> \[19\] (::Zygote.J{Tuple{getfield(Main, Symbol("##31#33")),Int64},Tuple{getfield(Main, Symbol("##31#33")),Int64,getfield(Zygote, Symbol("##796#back2#450")){getfield(Zygote, Symbol("##448#449")){Int64,Int64}},Zygote.J{Tuple{typeof(derivative),getfield(Main, Symbol("##32#34")){Int64},Int64},Tuple{typeof(derivative),getfield(Main, Symbol("##32#34")){Int64},Int64,getfield(Zygote, Symbol("##148#back2#115")){getfield(Zygote, Symbol("##111#113")){1,Int64}},Zygote.J{Tuple{typeof(gradient),getfield(Main, Symbol("##32#34")){Int64},Int64},Tuple{typeof(gradient)}}}},getfield(Zygote, Symbol("##194#back2#147")){Zygote.Jnew{getfield(Main, Symbol("##32#34")){Int64},Nothing}}}})(::Int64) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface2.jl:0
> \[20\] (::getfield(Zygote, Symbol("##66#67")){Zygote.J{Tuple{getfield(Main, Symbol("##31#33")),Int64},Tuple{getfield(Main, Symbol("##31#33")),Int64,getfield(Zygote, Symbol("##796#back2#450")){getfield(Zygote, Symbol("##448#449")){Int64,Int64}},Zygote.J{Tuple{typeof(derivative),getfield(Main, Symbol("##32#34")){Int64},Int64},Tuple{typeof(derivative),getfield(Main, Symbol("##32#34")){Int64},Int64,getfield(Zygote, Symbol("##148#back2#115")){getfield(Zygote, Symbol("##111#113")){1,Int64}},Zygote.J{Tuple{typeof(gradient),getfield(Main, Symbol("##32#34")){Int64},Int64},Tuple{typeof(gradient)}}}},getfield(Zygote, Symbol("##194#back2#147")){Zygote.Jnew{getfield(Main, Symbol("##32#34")){Int64},Nothing}}}}})(::Int64) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface.jl:28
> \[21\] gradient(::Function, ::Int64) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface.jl:34
> \[22\] derivative(::Function, ::Int64) at C:\\Users\\han\\.julia\\packages\\Zygote\\5mNII\\src\\compiler\\interface.jl:37
> \[23\] top-level scope at none:0
> \`\`\`

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