# Error when getting grads of an ensemble simulation with the newest packages

**URL:** <https://discourse.julialang.org/t/error-when-getting-grads-of-an-ensemble-simulation-with-the-newest-packages/56019>\
**Category:** Machine Learning\
**Tags:** question, diffeq, flux\
**Created:** [February 25, 2021, 2:36pm UTC](https://discourse.julialang.org/t/error-when-getting-grads-of-an-ensemble-simulation-with-the-newest-packages/56019 "2021-02-25T14:36:40Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![MikeKlocCZ](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mikekloccz/32/15357_2.png) [@MikeKlocCZ](https://discourse.julialang.org/u/MikeKlocCZ)\
**Post date:** [February 25, 2021, 2:36pm UTC](https://discourse.julialang.org/t/error-when-getting-grads-of-an-ensemble-simulation-with-the-newest-packages/56019/1 "2021-02-25T14:36:40Z")

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Hello everyone,

I updated to the newest packages of Zygote and Flux and I get error apparently related to the paralelization of an ensemble simulation

```julia
using DifferentialEquations, Flux, DiffEqFlux
using DiffEqSensitivity
using Random

function dt!(du, u, p, t)
  x, y = u
  α, β, δ, γ = p
  du[1] = dx = α*x - β*x*y
  du[2] = dy = -δ*y + γ*x*y
end

n_par=3
Random.seed!(2)
u0=rand(2,n_par)
u0[:,1] = [1.0,1.0]
tspan = (0.0, 10.0)
p = [2.2, 1.0, 2.0, 0.4]
prob_ode = ODEProblem(dt!, u0[:,1], tspan)

function test_loss(p1,prob)

	function prob_func(prob, i, repeat)
		@show i
		remake(prob,u0=u0[:,i])
	end

	#define ensemble problem
	ensembleprob = EnsembleProblem(prob,prob_func = prob_func)

	u = Array(solve(ensembleprob, EM(),trajectories=n_par,
	ensemblealg=EnsembleThreads(), p=p,
	sensealg = ForwardDiffSensitivity(),
	saveat = 0.1, dt=0.001))[:,end,:]
	loss=sum(u)
	return loss
end

#testing backprop
ps = Flux.params(p)
@time gs = gradient(ps) do
	test_loss(p,prob_ode)
end

#ERROR
ERROR: Compiling Tuple{typeof(Base.Threads.threading_run),SciMLBase.var"#400#threadsfor_fun#446"{SciMLBase.var"#443#445"{Base.Iterators.Pairs{Symbol,Any,NTuple{5,Symbol},NamedTuple{(:ensemblealg, :p, :sensealg, :saveat, :dt),Tuple{EnsembleThreads,Array{Float64,1},ForwardDiffSensitivity{0,nothing},Float64,Float64}}},EnsembleProblem{ODEProblem{Array{Float64,1},Tuple{Float64,Float64},true,SciMLBase.NullParameters,ODEFunction{true,typeof(dt!),LinearAlgebra.UniformScaling{Bool},Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,typeof(SciMLBase.DEFAULT_OBSERVED),Nothing},Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}},SciMLBase.StandardODEProblem},var"#prob_func#7",typeof(SciMLBase.DEFAULT_OUTPUT_FUNC),typeof(SciMLBase.DEFAULT_REDUCTION),Nothing},EM{true},UnitRange{Int64},Int64,Int64},Tuple{UnitRange{Int64}},Array{Array{T,1} where T,1},UnitRange{Int64}}}: try/catch is not supported.

```

The versions of the packages are:  
[aae7a2af] DiffEqFlux v1.34.0  
[41bf760c] DiffEqSensitivity v6.42.0  
[0c46a032] DifferentialEquations v6.16.0  
[587475ba] Flux v0.11.6  
[e88e6eb3] Zygote v0.6.2

For oler these versions the code works:  
[aae7a2af] DiffEqFlux v1.23.0  
[41bf760c] DiffEqSensitivity v6.33.0  
[0c46a032] DifferentialEquations v6.15.0  
[587475ba] Flux v0.11.1  
[e88e6eb3] Zygote v0.5.9

Any ideas what’s wrong?

---

<div class="post-metadata">

**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [March 3, 2021, 5:29pm UTC](https://discourse.julialang.org/t/error-when-getting-grads-of-an-ensemble-simulation-with-the-newest-packages/56019/2 "2021-03-03T17:29:58Z")

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It was a regression from the SciMLBase change. Fixed in [Fix AD of ensemble problems with threading by ChrisRackauckas · Pull Request #647 · SciML/DiffEqBase.jl · GitHub](https://github.com/SciML/DiffEqBase.jl/pull/647)

---

<div class="post-metadata">

**Author:** ![MikeKlocCZ](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mikekloccz/32/15357_2.png) [@MikeKlocCZ](https://discourse.julialang.org/u/MikeKlocCZ)\
**Post date:** [March 4, 2021, 9:11am UTC](https://discourse.julialang.org/t/error-when-getting-grads-of-an-ensemble-simulation-with-the-newest-packages/56019/3 "2021-03-04T09:11:12Z")

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Great, thanks!