# Accelerate autodiff in Zygote.jl
**URL:** https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454
**Category:** Performance
**Tags:** zygote, autodiff
**Created:** [August 16, 2021, 1:24am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454 "2021-08-16T01:24:45Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@Richard-Li](https://discourse.julialang.org/u/Richard-Li)
#### Post date: [August 16, 2021, 1:24am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/1 "2021-08-16T01:24:45Z")
Hi there,
I’d like to know if there is any **performance tip** for using Zygote.jl.
I am calculating the Hessian matrix using autodiff, and now the autodiff part runs quite slow, and I’d like to accelerate it.
e.g.
```julia
4.369689 seconds (7.95 M allocations: 1.199 GiB, 5.27% gc time)
Above: @time loss = myfunc(x, other_args)
10.895003 seconds (26.71 M allocations: 2.392 GiB, 5.95% gc time)
Above: @time ∂l∂x, _ = gradient(myfunc, x, other_args)
480.086188 seconds (285.59 M allocations: 201.816 GiB, 4.54% gc time)
Above: @time ∂2l∂2x = Zygote.hessian(f, x)
```
Is there any good way for **performance optimization of autodiff**? (like parallelization, or leveraging sparcity of matrix, or reducing memory IO? and how?)
Thx for any reply!
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [August 16, 2021, 1:36am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/2 "2021-08-16T01:36:57Z")
Zygote’s hessian is just bad. Try and see if Diffractor works on your problem (though it’s still very early for it)
---
### Author:  [@Richard-Li](https://discourse.julialang.org/u/Richard-Li)
#### Post date: [August 16, 2021, 2:00am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/3 "2021-08-16T02:00:45Z")
Thanks, I’ll check it out!
---
### Author:  [@Richard-Li](https://discourse.julialang.org/u/Richard-Li)
#### Post date: [August 18, 2021, 9:20am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/4 "2021-08-18T09:20:05Z")
Hi, I used `] add https://github.com/JuliaDiff/Diffractor.jl.git` to get Diffractor, but I met some precompiling error:
```julia
julia> using Diffractor
[Info: Precompiling Diffractor [9f5e2b26-1114-432f-b630-d3fe2085c51c]
ERROR: LoadError: LoadError: LoadError: UndefVarError: @aggressive_constprop not defined
Stacktrace:
[1] include(::Function, ::Module, ::String) at ./Base.jl:380
[2] include at ./Base.jl:368 [inlined]
[3] include(::String) at /root/.julia/packages/Diffractor/2Ott3/src/Diffractor.jl:1
[4] top-level scope at /root/.julia/packages/Diffractor/2Ott3/src/Diffractor.jl:7
[5] include(::Function, ::Module, ::String) at ./Base.jl:380
[6] include(::Module, ::String) at ./Base.jl:368
[7] top-level scope at none:2
[8] eval at ./boot.jl:331 [inlined]
[9] eval(::Expr) at ./client.jl:467
[10] top-level scope at ./none:3
in expression starting at /root/.julia/packages/Diffractor/2Ott3/src/runtime.jl:3
in expression starting at /root/.julia/packages/Diffractor/2Ott3/src/runtime.jl:3
in expression starting at /root/.julia/packages/Diffractor/2Ott3/src/Diffractor.jl:7
ERROR: Failed to precompile Diffractor [9f5e2b26-1114-432f-b630-d3fe2085c51c] to /root/.julia/compiled/v1.5/Diffractor/vzwwW_E53n4.ji.
Stacktrace:
[1] error(::String) at ./error.jl:33
[2] compilecache(::Base.PkgId, ::String) at ./loading.jl:1305
[3] _require(::Base.PkgId) at ./loading.jl:1030
[4] require(::Base.PkgId) at ./loading.jl:928
[5] require(::Module, ::Symbol) at ./loading.jl:923
[6] eval at ./boot.jl:331 [inlined]
[7] eval at ./Base.jl:39 [inlined]
[8] repleval(::Module, ::Expr, ::String) at /root/.vscode-server-insiders/extensions/julialang.language-julia-1.3.30/scripts/packages/VSCodeServer/src/repl.jl:157
[9] (::VSCodeServer.var"#69#71"{Module,Expr,REPL.LineEditREPL,REPL.LineEdit.Prompt})() at /root/.vscode-server-insiders/extensions/julialang.language-julia-1.3.30/scripts/packages/VSCodeServer/src/repl.jl:123
[10] with_logstate(::Function, ::Any) at ./logging.jl:408
[11] with_logger at ./logging.jl:514 [inlined]
[12] (::VSCodeServer.var"#68#70"{Module,Expr,REPL.LineEditREPL,REPL.LineEdit.Prompt})() at /root/.vscode-server-insiders/extensions/julialang.language-julia-1.3.30/scripts/packages/VSCodeServer/src/repl.jl:124
[13] #invokelatest#1 at ./essentials.jl:710 [inlined]
[14] invokelatest(::Any) at ./essentials.jl:709
[15] macro expansion at /root/.vscode-server-insiders/extensions/julialang.language-julia-1.3.30/scripts/packages/VSCodeServer/src/eval.jl:34 [inlined]
[16] (::VSCodeServer.var"#53#54")() at ./task.jl:356
```
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [August 18, 2021, 9:25am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/5 "2021-08-18T09:25:36Z")
It requires v1.7
---
### Author:  [@Richard-Li](https://discourse.julialang.org/u/Richard-Li)
#### Post date: [August 18, 2021, 9:28am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/6 "2021-08-18T09:28:31Z")
Thx! Do you mean Julia v1.7 beta?
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [August 18, 2021, 9:28am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/7 "2021-08-18T09:28:46Z")
Yes
---
### Author:  [@Richard-Li](https://discourse.julialang.org/u/Richard-Li)
#### Post date: [August 18, 2021, 9:29am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/8 "2021-08-18T09:29:46Z")
Get it! 😀
---
### Author:  [@Vinicius\_Viena](https://discourse.julialang.org/u/Vinicius_Viena)
#### Post date: [June 15, 2022, 9:56am UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/9 "2022-06-15T09:56:39Z")
Hey, @Richard-Li. Did you managed to set up hessian calculation with Diffractor? I am facing a similar problem - Hessians are too slow in Zygote. However, it seems that Diffractor.jl does not have a method for hessian, only gradients ):
---
### Author:  [@IlyaOrson](https://discourse.julialang.org/u/IlyaOrson)
#### Post date: [June 15, 2022, 12:26pm UTC](https://discourse.julialang.org/t/accelerate-autodiff-in-zygote-jl/66454/10 "2022-06-15T12:26:35Z")
You could try forward over reverse. Here you can see an example [Optimization.jl/zygote.jl at master · SciML/Optimization.jl · GitHub](https://github.com/SciML/Optimization.jl/blob/master/src/function/zygote.jl)