SplitODEProblem doesn't work with ForwardDiff in in-place mode.

[ctessum]

Describe the bug 🐞

I would like to use ForwardDiff to calculate the sensitivity of an ODE system using a split problem. It currently works with an out-of-place ODE function, but it doesn't work with an in-place function.

Expected behavior

I would expect it to work both in place and out-of-place.

Minimal Reproducible Example 👇

using DifferentialEquations
using ForwardDiff
using LinearAlgebra
using SciMLSensitivity
using Test

f1(du, u, p, t) = du .= -p
f1(u, p, t) = -p

f2(du, u, p, t) = du .= 2p
f2(u, p, t) = 2p

p = rand(3)
prob = SplitODEProblem{false}(f1, f2, zeros(3), (0, 1), p)
sol = solve(prob)
@test sol[end] ≈ p # 0 - p + 2p = p

function loss(p)
    u0 = Vector{eltype(p)}(prob.u0)
    _prob = remake(prob, u0=u0, p=p)
    sol = solve(_prob)
    norm(sol[end])
end

ForwardDiff.gradient(loss, p) # Works with out-of-place problem

prob = SplitODEProblem{true}(f1, f2, zeros(3), (0, 1), p)

ForwardDiff.gradient(loss, p) # Does not work with in-place problem

Error & Stacktrace ⚠️

ERROR: MethodError: no method matching Float64(::ForwardDiff.Dual{ForwardDiff.Tag{typeof(loss), Float64}, Float64, 3})
The type `Float64` exists, but no method is defined for this combination of argument types when trying to construct it.

Closest candidates are:
  (::Type{T})(::Real, ::RoundingMode) where T<:AbstractFloat
   @ Base rounding.jl:265
  (::Type{T})(::T) where T<:Number
   @ Core boot.jl:900
  Float64(::Int16)
   @ Base float.jl:239
  ...

Stacktrace:
  [1] convert(::Type{Float64}, x::ForwardDiff.Dual{ForwardDiff.Tag{typeof(loss), Float64}, Float64, 3})
    @ Base ./number.jl:7
  [2] setindex!(A::Memory{Float64}, x::ForwardDiff.Dual{ForwardDiff.Tag{typeof(loss), Float64}, Float64, 3}, i1::Int64)
    @ Base ./genericmemory.jl:243
  [3] unsafe_copyto!(dest::Memory{Float64}, doffs::Int64, src::Memory{ForwardDiff.Dual{…}}, soffs::Int64, n::Int64)
    @ Base ./genericmemory.jl:153
  [4] unsafe_copyto!
    @ ./genericmemory.jl:133 [inlined]
  [5] _copyto_impl!
    @ ./array.jl:308 [inlined]
  [6] copyto!
    @ ./array.jl:294 [inlined]
  [7] copyto!
    @ ./array.jl:319 [inlined]
  [8] copyto!
    @ ./broadcast.jl:961 [inlined]
  [9] copyto!
    @ ./broadcast.jl:920 [inlined]
 [10] materialize!
    @ ./broadcast.jl:878 [inlined]
 [11] materialize!
    @ ./broadcast.jl:875 [inlined]
 [12] f1(du::Vector{Float64}, u::Vector{ForwardDiff.Dual{…}}, p::Vector{ForwardDiff.Dual{…}}, t::Float64)
    @ Main ~/...:10
 [13] ODEFunction
    @ ~/.julia/packages/SciMLBase/YTOjh/src/scimlfunctions.jl:2468 [inlined]
 [14] (::SplitFunction{…})(du::Vector{…}, u::Vector{…}, p::Vector{…}, t::Float64)
    @ SciMLBase ~/.julia/packages/SciMLBase/YTOjh/src/scimlfunctions.jl:2485
 [15] initialize!
    @ ~/.julia/packages/OrdinaryDiffEqTsit5/DHYtz/src/tsit_perform_step.jl:175 [inlined]
 [16] initialize!(integrator::OrdinaryDiffEqCore.ODEIntegrator{…}, cache::OrdinaryDiffEqCore.DefaultCache{…})
    @ OrdinaryDiffEqCore ~/.julia/packages/OrdinaryDiffEqCore/yTEch/src/perform_step/composite_perform_step.jl:38
 [17] __init(prob::ODEProblem{…}, alg::CompositeAlgorithm{…}, timeseries_init::Tuple{}, ts_init::Tuple{}, ks_init::Tuple{}, recompile::Type{…}; saveat::Tuple{}, tstops::Tuple{}, d_discontinuities::Tuple{}, save_idxs::Nothing, save_everystep::Bool, save_on::Bool, save_start::Bool, save_end::Nothing, callback::Nothing, dense::Bool, calck::Bool, dt::Float64, dtmin::Float64, dtmax::Float64, force_dtmin::Bool, adaptive::Bool, gamma::Rational{…}, abstol::Nothing, reltol::Nothing, qmin::Rational{…}, qmax::Int64, qsteady_min::Int64, qsteady_max::Int64, beta1::Nothing, beta2::Nothing, qoldinit::Rational{…}, controller::Nothing, fullnormalize::Bool, failfactor::Int64, maxiters::Int64, internalnorm::typeof(DiffEqBase.ODE_DEFAULT_NORM), internalopnorm::typeof(opnorm), isoutofdomain::typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), unstable_check::typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), verbose::Bool, timeseries_errors::Bool, dense_errors::Bool, advance_to_tstop::Bool, stop_at_next_tstop::Bool, initialize_save::Bool, progress::Bool, progress_steps::Int64, progress_name::String, progress_message::typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), progress_id::Symbol, userdata::Nothing, allow_extrapolation::Bool, initialize_integrator::Bool, alias::ODEAliasSpecifier, initializealg::OrdinaryDiffEqCore.DefaultInit, kwargs::@Kwargs{…})
    @ OrdinaryDiffEqCore ~/.julia/packages/OrdinaryDiffEqCore/yTEch/src/solve.jl:587
 [18] __init (repeats 5 times)
    @ ~/.julia/packages/OrdinaryDiffEqCore/yTEch/src/solve.jl:11 [inlined]
 [19] #__solve#62
    @ ~/.julia/packages/OrdinaryDiffEqCore/yTEch/src/solve.jl:6 [inlined]
 [20] __solve
    @ ~/.julia/packages/OrdinaryDiffEqCore/yTEch/src/solve.jl:1 [inlined]
 [21] solve_call(_prob::ODEProblem{…}, args::CompositeAlgorithm{…}; merge_callbacks::Bool, kwargshandle::Nothing, kwargs::@Kwargs{…})
    @ DiffEqBase ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:635
 [22] solve_call
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:592 [inlined]
 [23] #solve_up#44
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1124 [inlined]
 [24] solve_up
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1102 [inlined]
 [25] #solve#42
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1041 [inlined]
 [26] solve
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1029 [inlined]
 [27] #__solve#3
    @ ~/.julia/packages/OrdinaryDiffEqDefault/kOV75/src/default_alg.jl:48 [inlined]
 [28] __solve
    @ ~/.julia/packages/OrdinaryDiffEqDefault/kOV75/src/default_alg.jl:47 [inlined]
 [29] #__solve#63
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1432 [inlined]
 [30] __solve
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1423 [inlined]
 [31] #solve_call#35
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:635 [inlined]
 [32] solve_call(::ODEProblem{Vector{…}, Tuple{…}, true, Vector{…}, SplitFunction{…}, @Kwargs{}, SplitODEProblem{…}})
    @ DiffEqBase ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:592
 [33] solve_up(::ODEProblem{…}, ::Nothing, ::Vector{…}, ::Vector{…}; kwargs::@Kwargs{})
    @ DiffEqBase ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1108
 [34] solve_up
    @ ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1102 [inlined]
 [35] solve(::ODEProblem{…}; sensealg::Nothing, u0::Nothing, p::Nothing, wrap::Val{…}, kwargs::@Kwargs{})
    @ DiffEqBase ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1039
 [36] solve(::ODEProblem{Vector{…}, Tuple{…}, true, Vector{…}, SplitFunction{…}, @Kwargs{}, SplitODEProblem{…}})
    @ DiffEqBase ~/.julia/packages/DiffEqBase/l2ROR/src/solve.jl:1029
 [37] loss(p::Vector{ForwardDiff.Dual{ForwardDiff.Tag{typeof(loss), Float64}, Float64, 3}})
    @ Main ~/.../test4.md:24
 [38] vector_mode_dual_eval!
    @ ~/.julia/packages/ForwardDiff/UBbGT/src/apiutils.jl:24 [inlined]
 [39] vector_mode_gradient(f::typeof(loss), x::Vector{…}, cfg::ForwardDiff.GradientConfig{…})
    @ ForwardDiff ~/.julia/packages/ForwardDiff/UBbGT/src/gradient.jl:91
 [40] gradient
    @ ~/.julia/packages/ForwardDiff/UBbGT/src/gradient.jl:20 [inlined]
 [41] gradient(f::typeof(loss), x::Vector{…}, cfg::ForwardDiff.GradientConfig{…})
    @ ForwardDiff ~/.julia/packages/ForwardDiff/UBbGT/src/gradient.jl:17
 [42] gradient(f::typeof(loss), x::Vector{Float64})
    @ ForwardDiff ~/.julia/packages/ForwardDiff/UBbGT/src/gradient.jl:17
 [43] top-level scope
    @ ~/.../test4.md:32
Some type information was truncated. Use `show(err)` to see complete types.

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

Status `~/.../Project.toml`
⌃ [2169fc97] AlgebraicMultigrid v0.5.1
  [4fba245c] ArrayInterface v7.18.0
  [aae01518] BandedMatrices v1.9.1
  [ffab5731] BlockBandedMatrices v0.13.4
  [0a1fb500] BlockDiagonals v0.1.42
  [0c46a032] DifferentialEquations v7.16.0
  [f6369f11] ForwardDiff v0.10.38
  [63c18a36] KernelAbstractions v0.9.34
  [7ed4a6bd] LinearSolve v3.3.1
  [91a5bcdd] Plots v1.40.9
  [33c8b6b6] ProgressLogging v0.1.4
  [1ed8b502] SciMLSensitivity v7.74.0
  [2f01184e] SparseArrays v1.11.0
Info Packages marked with ⌃ have new versions available and may be upgradable.

• Output of using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)

  [47edcb42] ADTypes v1.13.0
  [621f4979] AbstractFFTs v1.5.0
  [7d9f7c33] Accessors v0.1.41
  [79e6a3ab] Adapt v4.1.1
⌃ [2169fc97] AlgebraicMultigrid v0.5.1
  [66dad0bd] AliasTables v1.1.3
  [a95523ee] AlmostBlockDiagonals v0.1.10
  [ec485272] ArnoldiMethod v0.4.0
  [4fba245c] ArrayInterface v7.18.0
  [4c555306] ArrayLayouts v1.11.0
  [a9b6321e] Atomix v1.1.0
  [aae01518] BandedMatrices v1.9.1
  [d1d4a3ce] BitFlags v0.1.9
  [62783981] BitTwiddlingConvenienceFunctions v0.1.6
  [8e7c35d0] BlockArrays v1.4.0
  [ffab5731] BlockBandedMatrices v0.13.4
  [0a1fb500] BlockDiagonals v0.1.42
  [764a87c0] BoundaryValueDiffEq v5.15.0
  [7227322d] BoundaryValueDiffEqAscher v1.4.0
  [56b672f2] BoundaryValueDiffEqCore v1.7.0
  [85d9eb09] BoundaryValueDiffEqFIRK v1.5.0
  [1a22d4ce] BoundaryValueDiffEqMIRK v1.5.0
  [9255f1d6] BoundaryValueDiffEqMIRKN v1.4.0
  [ed55bfe0] BoundaryValueDiffEqShooting v1.5.0
  [70df07ce] BracketingNonlinearSolve v1.1.0
  [fa961155] CEnum v0.5.0
  [2a0fbf3d] CPUSummary v0.2.6
  [7057c7e9] Cassette v0.3.14
  [082447d4] ChainRules v1.72.2
  [d360d2e6] ChainRulesCore v1.25.1
  [fb6a15b2] CloseOpenIntervals v0.1.13
  [944b1d66] CodecZlib v0.7.8
  [35d6a980] ColorSchemes v3.29.0
  [3da002f7] ColorTypes v0.12.0
  [c3611d14] ColorVectorSpace v0.11.0
  [5ae59095] Colors v0.13.0
  [38540f10] CommonSolve v0.2.4
  [bbf7d656] CommonSubexpressions v0.3.1
  [f70d9fcc] CommonWorldInvalidations v1.0.0
  [34da2185] Compat v4.16.0
  [a33af91c] CompositionsBase v0.1.2
  [2569d6c7] ConcreteStructs v0.2.3
  [f0e56b4a] ConcurrentUtilities v2.5.0
  [187b0558] ConstructionBase v1.5.8
  [d38c429a] Contour v0.6.3
  [adafc99b] CpuId v0.3.1
  [9a962f9c] DataAPI v1.16.0
  [864edb3b] DataStructures v0.18.20
  [e2d170a0] DataValueInterfaces v1.0.0
  [bcd4f6db] DelayDiffEq v5.52.0
  [8bb1440f] DelimitedFiles v1.9.1
  [2b5f629d] DiffEqBase v6.164.0
  [459566f4] DiffEqCallbacks v4.2.2
  [77a26b50] DiffEqNoiseProcess v5.24.1
  [163ba53b] DiffResults v1.1.0
  [b552c78f] DiffRules v1.15.1
  [0c46a032] DifferentialEquations v7.16.0
  [a0c0ee7d] DifferentiationInterface v0.6.41
  [b4f34e82] Distances v0.10.12
  [31c24e10] Distributions v0.25.117
  [ffbed154] DocStringExtensions v0.9.3
  [4e289a0a] EnumX v1.0.4
  [7da242da] Enzyme v0.13.30
  [f151be2c] EnzymeCore v0.8.8
  [460bff9d] ExceptionUnwrapping v0.1.11
  [d4d017d3] ExponentialUtilities v1.27.0
  [e2ba6199] ExprTools v0.1.10
⌅ [6b7a57c9] Expronicon v0.8.5
  [c87230d0] FFMPEG v0.4.2
  [9d29842c] FastAlmostBandedMatrices v0.1.4
  [7034ab61] FastBroadcast v0.3.5
  [9aa1b823] FastClosures v0.3.2
  [442a2c76] FastGaussQuadrature v1.0.2
  [a4df4552] FastPower v1.1.1
  [1a297f60] FillArrays v1.13.0
  [6a86dc24] FiniteDiff v2.27.0
  [26cc04aa] FiniteDifferences v0.12.32
  [53c48c17] FixedPointNumbers v0.8.5
  [1fa38f19] Format v1.3.7
  [f6369f11] ForwardDiff v0.10.38
  [f62d2435] FunctionProperties v0.1.2
  [069b7b12] FunctionWrappers v1.1.3
  [77dc65aa] FunctionWrappersWrappers v0.1.3
  [d9f16b24] Functors v0.5.2
  [0c68f7d7] GPUArrays v11.2.2
  [46192b85] GPUArraysCore v0.2.0
  [61eb1bfa] GPUCompiler v1.2.0
  [28b8d3ca] GR v0.73.13
  [c145ed77] GenericSchur v0.5.4
  [86223c79] Graphs v1.12.0
  [42e2da0e] Grisu v1.0.2
  [cd3eb016] HTTP v1.10.15
  [076d061b] HashArrayMappedTries v0.2.0
  [34004b35] HypergeometricFunctions v0.3.27
  [7869d1d1] IRTools v0.4.14
  [615f187c] IfElse v0.1.1
  [d25df0c9] Inflate v0.1.5
  [3587e190] InverseFunctions v0.1.17
  [92d709cd] IrrationalConstants v0.2.4
  [82899510] IteratorInterfaceExtensions v1.0.0
  [1019f520] JLFzf v0.1.9
  [692b3bcd] JLLWrappers v1.7.0
  [682c06a0] JSON v0.21.4
  [ccbc3e58] JumpProcesses v9.14.2
  [63c18a36] KernelAbstractions v0.9.34
  [ba0b0d4f] Krylov v0.9.10
  [929cbde3] LLVM v9.2.0
  [b964fa9f] LaTeXStrings v1.4.0
  [23fbe1c1] Latexify v0.16.6
  [10f19ff3] LayoutPointers v0.1.17
  [5078a376] LazyArrays v2.6.0
  [2d8b4e74] LevyArea v1.0.0
  [87fe0de2] LineSearch v0.1.4
  [d3d80556] LineSearches v7.3.0
  [7ed4a6bd] LinearSolve v3.3.1
  [2ab3a3ac] LogExpFunctions v0.3.29
  [e6f89c97] LoggingExtras v1.1.0
  [d8e11817] MLStyle v0.4.17
  [1914dd2f] MacroTools v0.5.15
  [d125e4d3] ManualMemory v0.1.8
  [a3b82374] MatrixFactorizations v3.0.1
  [bb5d69b7] MaybeInplace v0.1.4
  [739be429] MbedTLS v1.1.9
  [442fdcdd] Measures v0.3.2
  [e1d29d7a] Missings v1.2.0
  [46d2c3a1] MuladdMacro v0.2.4
  [d41bc354] NLSolversBase v7.8.3
  [2774e3e8] NLsolve v4.5.1
  [872c559c] NNlib v0.9.27
  [77ba4419] NaNMath v1.1.2
  [8913a72c] NonlinearSolve v4.4.0
  [be0214bd] NonlinearSolveBase v1.5.0
  [5959db7a] NonlinearSolveFirstOrder v1.3.0
  [9a2c21bd] NonlinearSolveQuasiNewton v1.2.0
  [26075421] NonlinearSolveSpectralMethods v1.1.0
  [d8793406] ObjectFile v0.4.3
  [4d8831e6] OpenSSL v1.4.3
  [429524aa] Optim v1.11.0
  [3bd65402] Optimisers v0.4.4
  [bac558e1] OrderedCollections v1.8.0
  [1dea7af3] OrdinaryDiffEq v6.91.0
  [89bda076] OrdinaryDiffEqAdamsBashforthMoulton v1.2.0
  [6ad6398a] OrdinaryDiffEqBDF v1.2.0
  [bbf590c4] OrdinaryDiffEqCore v1.18.1
  [50262376] OrdinaryDiffEqDefault v1.3.0
  [4302a76b] OrdinaryDiffEqDifferentiation v1.4.0
  [9286f039] OrdinaryDiffEqExplicitRK v1.1.0
  [e0540318] OrdinaryDiffEqExponentialRK v1.3.0
  [becaefa8] OrdinaryDiffEqExtrapolation v1.4.0
  [5960d6e9] OrdinaryDiffEqFIRK v1.7.0
  [101fe9f7] OrdinaryDiffEqFeagin v1.1.0
  [d3585ca7] OrdinaryDiffEqFunctionMap v1.1.1
  [d28bc4f8] OrdinaryDiffEqHighOrderRK v1.1.0
  [9f002381] OrdinaryDiffEqIMEXMultistep v1.2.0
  [521117fe] OrdinaryDiffEqLinear v1.1.0
  [1344f307] OrdinaryDiffEqLowOrderRK v1.2.0
  [b0944070] OrdinaryDiffEqLowStorageRK v1.2.1
  [127b3ac7] OrdinaryDiffEqNonlinearSolve v1.4.0
  [c9986a66] OrdinaryDiffEqNordsieck v1.1.0
  [5dd0a6cf] OrdinaryDiffEqPDIRK v1.2.0
  [5b33eab2] OrdinaryDiffEqPRK v1.1.0
  [04162be5] OrdinaryDiffEqQPRK v1.1.0
  [af6ede74] OrdinaryDiffEqRKN v1.1.0
  [43230ef6] OrdinaryDiffEqRosenbrock v1.5.0
  [2d112036] OrdinaryDiffEqSDIRK v1.2.0
  [669c94d9] OrdinaryDiffEqSSPRK v1.2.0
  [e3e12d00] OrdinaryDiffEqStabilizedIRK v1.2.0
  [358294b1] OrdinaryDiffEqStabilizedRK v1.1.0
  [fa646aed] OrdinaryDiffEqSymplecticRK v1.3.0
  [b1df2697] OrdinaryDiffEqTsit5 v1.1.0
  [79d7bb75] OrdinaryDiffEqVerner v1.1.1
  [90014a1f] PDMats v0.11.32
  [65ce6f38] PackageExtensionCompat v1.0.2
  [d96e819e] Parameters v0.12.3
  [69de0a69] Parsers v2.8.1
  [b98c9c47] Pipe v1.3.0
  [ccf2f8ad] PlotThemes v3.3.0
  [995b91a9] PlotUtils v1.4.3
  [91a5bcdd] Plots v1.40.9
  [e409e4f3] PoissonRandom v0.4.4
  [f517fe37] Polyester v0.7.16
  [1d0040c9] PolyesterWeave v0.2.2
  [85a6dd25] PositiveFactorizations v0.2.4
  [d236fae5] PreallocationTools v0.4.25
  [aea7be01] PrecompileTools v1.2.1
  [21216c6a] Preferences v1.4.3
  [33c8b6b6] ProgressLogging v0.1.4
  [43287f4e] PtrArrays v1.3.0
  [1fd47b50] QuadGK v2.11.2
  [74087812] Random123 v1.7.0
  [e6cf234a] RandomNumbers v1.6.0
  [c1ae055f] RealDot v0.1.0
  [3cdcf5f2] RecipesBase v1.3.4
  [01d81517] RecipesPipeline v0.6.12
  [731186ca] RecursiveArrayTools v3.29.0
  [189a3867] Reexport v1.2.2
  [05181044] RelocatableFolders v1.0.1
  [ae029012] Requires v1.3.0
  [ae5879a3] ResettableStacks v1.1.1
  [37e2e3b7] ReverseDiff v1.15.3
  [708f8203] Richardson v1.4.2
  [79098fc4] Rmath v0.8.0
  [7e49a35a] RuntimeGeneratedFunctions v0.5.13
  [94e857df] SIMDTypes v0.1.0
  [0bca4576] SciMLBase v2.74.1
  [19f34311] SciMLJacobianOperators v0.1.1
  [c0aeaf25] SciMLOperators v0.3.12
  [1ed8b502] SciMLSensitivity v7.74.0
  [53ae85a6] SciMLStructures v1.6.1
  [7e506255] ScopedValues v1.3.0
  [6c6a2e73] Scratch v1.2.1
  [efcf1570] Setfield v1.1.1
  [992d4aef] Showoff v1.0.3
  [777ac1f9] SimpleBufferStream v1.2.0
  [727e6d20] SimpleNonlinearSolve v2.1.0
  [699a6c99] SimpleTraits v0.9.4
  [ce78b400] SimpleUnPack v1.1.0
  [a2af1166] SortingAlgorithms v1.2.1
  [47a9eef4] SparseDiffTools v2.23.1
  [dc90abb0] SparseInverseSubset v0.1.2
  [0a514795] SparseMatrixColorings v0.4.13
  [276daf66] SpecialFunctions v2.5.0
  [860ef19b] StableRNGs v1.0.2
  [aedffcd0] Static v1.1.1
  [0d7ed370] StaticArrayInterface v1.8.0
  [90137ffa] StaticArrays v1.9.12
  [1e83bf80] StaticArraysCore v1.4.3
  [10745b16] Statistics v1.11.1
  [82ae8749] StatsAPI v1.7.0
  [2913bbd2] StatsBase v0.34.4
  [4c63d2b9] StatsFuns v1.3.2
  [9672c7b4] SteadyStateDiffEq v2.4.1
  [789caeaf] StochasticDiffEq v6.74.0
  [7792a7ef] StrideArraysCore v0.5.7
  [09ab397b] StructArrays v0.7.0
  [53d494c1] StructIO v0.3.1
  [c3572dad] Sundials v4.26.1
  [2efcf032] SymbolicIndexingInterface v0.3.37
  [3783bdb8] TableTraits v1.0.1
  [bd369af6] Tables v1.12.0
  [62fd8b95] TensorCore v0.1.1
  [8290d209] ThreadingUtilities v0.5.2
  [a759f4b9] TimerOutputs v0.5.26
  [9f7883ad] Tracker v0.2.37
  [3bb67fe8] TranscodingStreams v0.11.3
  [781d530d] TruncatedStacktraces v1.4.0
  [5c2747f8] URIs v1.5.1
  [3a884ed6] UnPack v1.0.2
  [1cfade01] UnicodeFun v0.4.1
  [1986cc42] Unitful v1.22.0
  [45397f5d] UnitfulLatexify v1.6.4
  [013be700] UnsafeAtomics v0.3.0
  [41fe7b60] Unzip v0.2.0
  [19fa3120] VertexSafeGraphs v0.2.0
⌃ [e88e6eb3] Zygote v0.6.75
  [700de1a5] ZygoteRules v0.2.7
  [6e34b625] Bzip2_jll v1.0.9+0
  [83423d85] Cairo_jll v1.18.2+1
  [ee1fde0b] Dbus_jll v1.14.10+0
  [7cc45869] Enzyme_jll v0.0.172+0
  [2702e6a9] EpollShim_jll v0.0.20230411+1
  [2e619515] Expat_jll v2.6.5+0
⌅ [b22a6f82] FFMPEG_jll v4.4.4+1
  [a3f928ae] Fontconfig_jll v2.15.0+0
  [d7e528f0] FreeType2_jll v2.13.3+1
  [559328eb] FriBidi_jll v1.0.16+0
  [0656b61e] GLFW_jll v3.4.0+2
  [d2c73de3] GR_jll v0.73.13+0
  [78b55507] Gettext_jll v0.21.0+0
  [7746bdde] Glib_jll v2.82.4+0
  [3b182d85] Graphite2_jll v1.3.14+1
  [2e76f6c2] HarfBuzz_jll v8.5.0+0
  [1d5cc7b8] IntelOpenMP_jll v2025.0.4+0
  [aacddb02] JpegTurbo_jll v3.1.1+0
  [c1c5ebd0] LAME_jll v3.100.2+0
  [88015f11] LERC_jll v4.0.1+0
  [dad2f222] LLVMExtra_jll v0.0.35+0
  [1d63c593] LLVMOpenMP_jll v18.1.7+0
  [dd4b983a] LZO_jll v2.10.3+0
⌅ [e9f186c6] Libffi_jll v3.2.2+2
  [d4300ac3] Libgcrypt_jll v1.11.0+0
  [7e76a0d4] Libglvnd_jll v1.7.0+0
  [7add5ba3] Libgpg_error_jll v1.51.1+0
  [94ce4f54] Libiconv_jll v1.18.0+0
  [4b2f31a3] Libmount_jll v2.40.3+0
  [89763e89] Libtiff_jll v4.7.1+0
  [38a345b3] Libuuid_jll v2.40.3+0
  [856f044c] MKL_jll v2025.0.1+1
  [e7412a2a] Ogg_jll v1.3.5+1
  [458c3c95] OpenSSL_jll v3.0.16+0
  [efe28fd5] OpenSpecFun_jll v0.5.6+0
  [91d4177d] Opus_jll v1.3.3+0
  [36c8627f] Pango_jll v1.56.1+0
⌅ [30392449] Pixman_jll v0.43.4+0
⌅ [c0090381] Qt6Base_jll v6.7.1+1
⌅ [629bc702] Qt6Declarative_jll v6.7.1+2
⌅ [ce943373] Qt6ShaderTools_jll v6.7.1+1
⌃ [e99dba38] Qt6Wayland_jll v6.7.1+1
  [f50d1b31] Rmath_jll v0.5.1+0
⌅ [fb77eaff] Sundials_jll v5.2.3+0
  [a44049a8] Vulkan_Loader_jll v1.3.243+0
  [a2964d1f] Wayland_jll v1.21.0+2
  [2381bf8a] Wayland_protocols_jll v1.36.0+0
  [02c8fc9c] XML2_jll v2.13.6+0
  [aed1982a] XSLT_jll v1.1.42+0
  [ffd25f8a] XZ_jll v5.6.4+1
  [f67eecfb] Xorg_libICE_jll v1.1.1+0
  [c834827a] Xorg_libSM_jll v1.2.4+0
  [4f6342f7] Xorg_libX11_jll v1.8.6+3
  [0c0b7dd1] Xorg_libXau_jll v1.0.12+0
  [935fb764] Xorg_libXcursor_jll v1.2.3+0
  [a3789734] Xorg_libXdmcp_jll v1.1.5+0
  [1082639a] Xorg_libXext_jll v1.3.6+3
  [d091e8ba] Xorg_libXfixes_jll v6.0.0+0
  [a51aa0fd] Xorg_libXi_jll v1.8.2+0
  [d1454406] Xorg_libXinerama_jll v1.1.5+0
  [ec84b674] Xorg_libXrandr_jll v1.5.4+0
  [ea2f1a96] Xorg_libXrender_jll v0.9.11+1
  [14d82f49] Xorg_libpthread_stubs_jll v0.1.2+0
  [c7cfdc94] Xorg_libxcb_jll v1.17.0+3
  [cc61e674] Xorg_libxkbfile_jll v1.1.2+1
  [e920d4aa] Xorg_xcb_util_cursor_jll v0.1.4+0
  [12413925] Xorg_xcb_util_image_jll v0.4.0+1
  [2def613f] Xorg_xcb_util_jll v0.4.0+1
  [975044d2] Xorg_xcb_util_keysyms_jll v0.4.0+1
  [0d47668e] Xorg_xcb_util_renderutil_jll v0.3.9+1
  [c22f9ab0] Xorg_xcb_util_wm_jll v0.4.1+1
  [35661453] Xorg_xkbcomp_jll v1.4.6+1
  [33bec58e] Xorg_xkeyboard_config_jll v2.39.0+0
  [c5fb5394] Xorg_xtrans_jll v1.5.1+0
  [3161d3a3] Zstd_jll v1.5.7+0
  [35ca27e7] eudev_jll v3.2.9+0
  [214eeab7] fzf_jll v0.56.3+0
  [1a1c6b14] gperf_jll v3.1.1+1
  [a4ae2306] libaom_jll v3.11.0+0
  [0ac62f75] libass_jll v0.15.2+0
  [1183f4f0] libdecor_jll v0.2.2+0
  [2db6ffa8] libevdev_jll v1.11.0+0
  [f638f0a6] libfdk_aac_jll v2.0.3+0
  [36db933b] libinput_jll v1.18.0+0
  [b53b4c65] libpng_jll v1.6.46+0
  [f27f6e37] libvorbis_jll v1.3.7+2
  [009596ad] mtdev_jll v1.1.6+0
  [1317d2d5] oneTBB_jll v2022.0.0+0
⌅ [1270edf5] x264_jll v2021.5.5+0
⌅ [dfaa095f] x265_jll v3.5.0+0
  [d8fb68d0] xkbcommon_jll v1.4.1+2
  [0dad84c5] ArgTools v1.1.2
  [56f22d72] Artifacts v1.11.0
  [2a0f44e3] Base64 v1.11.0
  [ade2ca70] Dates v1.11.0
  [8ba89e20] Distributed v1.11.0
  [f43a241f] Downloads v1.6.0
  [7b1f6079] FileWatching v1.11.0
  [9fa8497b] Future v1.11.0
  [b77e0a4c] InteractiveUtils v1.11.0
  [4af54fe1] LazyArtifacts v1.11.0
  [b27032c2] LibCURL v0.6.4
  [76f85450] LibGit2 v1.11.0
  [8f399da3] Libdl v1.11.0
  [37e2e46d] LinearAlgebra v1.11.0
  [56ddb016] Logging v1.11.0
  [d6f4376e] Markdown v1.11.0
  [a63ad114] Mmap v1.11.0
  [ca575930] NetworkOptions v1.2.0
  [44cfe95a] Pkg v1.11.0
  [de0858da] Printf v1.11.0
  [3fa0cd96] REPL v1.11.0
  [9a3f8284] Random v1.11.0
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization v1.11.0
  [1a1011a3] SharedArrays v1.11.0
  [6462fe0b] Sockets v1.11.0
  [2f01184e] SparseArrays v1.11.0
  [f489334b] StyledStrings v1.11.0
  [4607b0f0] SuiteSparse
  [fa267f1f] TOML v1.0.3
  [a4e569a6] Tar v1.10.0
  [8dfed614] Test v1.11.0
  [cf7118a7] UUIDs v1.11.0
  [4ec0a83e] Unicode v1.11.0
  [e66e0078] CompilerSupportLibraries_jll v1.1.1+0
  [deac9b47] LibCURL_jll v8.6.0+0
  [e37daf67] LibGit2_jll v1.7.2+0
  [29816b5a] LibSSH2_jll v1.11.0+1
  [c8ffd9c3] MbedTLS_jll v2.28.6+0
  [14a3606d] MozillaCACerts_jll v2023.12.12
  [4536629a] OpenBLAS_jll v0.3.27+1
  [05823500] OpenLibm_jll v0.8.1+2
  [efcefdf7] PCRE2_jll v10.42.0+1
  [bea87d4a] SuiteSparse_jll v7.7.0+0
  [83775a58] Zlib_jll v1.2.13+1
  [8e850b90] libblastrampoline_jll v5.11.0+0
  [8e850ede] nghttp2_jll v1.59.0+0
  [3f19e933] p7zip_jll v17.4.0+2

• Output of versioninfo()

Julia Version 1.11.2
Commit 5e9a32e7af2 (2024-12-01 20:02 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 8 × Apple M1
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, apple-m1)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 1

Additional context

My understanding from the debugger is that the cache for du is not getting converted to dual numbers for some reason.

[ChrisRackauckas]

The issue is that it's doing a fallback on the differentiation to the non-split case. The best thing would be to specialize the differentiation for split ODEs, but until we do that... we should also make the fallback work.

The issue with the fallback is that it gets the type of the func_cache wrong. The fix is:

function SciMLBase.SplitODEProblem{iip}(f::SplitFunction, u0, tspan, p = NullParameters();
        kwargs...) where {iip}
    if f._func_cache === nothing && iip
        _func_cache = DiffCache(u0, 1) # better to choose the chunk based on ForwardDiff.chunksize(u0)
        f = SplitFunction{iip}(f.f1, f.f2; mass_matrix = f.mass_matrix,
            _func_cache = _func_cache, analytic = f.analytic)
    end
    ODEProblem(f, u0, tspan, p, SplitODEProblem{iip}(); kwargs...)
end

function (f::SciMLBase.SplitFunction)(du, u, p, t)
    tmp = get_tmp(f._func_cache, u)
    f.f1(tmp, u, p, t)
    f.f2(du, u, p, t)
    du .+= tmp
end

But we don't want a SciMLBase dependency on PreallocationTools.jl, so it takes a bit of restructuring to do this better.