Warning: Internal error

[ufechner7]

Describe the bug 🐞

ModelingToolkit v9.28.0 prints a lot of warnings (Internal error) for a script that was running fine with older versions of ModelingToolkit.

Expected behavior

No warning for the code that worked before.

Minimal Reproducible Example 👇

# Example two: Falling mass, attached to linear spring
using ModelingToolkit, OrdinaryDiffEq, LinearAlgebra
using ModelingToolkit: t_nounits as t, D_nounits as D

G_EARTH::Vector{Float64} = [0.0, 0.0, -9.81]    # gravitational acceleration     [m/s²]
L0::Float64 = -10.0                             # initial spring length      [m]

# defing the model, Z component upwards
@parameters mass=1.0 c_spring=50.0 damping=0.5 l0=L0
@variables   pos(t)[1:3] = [0.0, 0.0,  L0]
@variables   vel(t)[1:3] = [0.0, 0.0,  0.0] 
@variables   acc(t)[1:3] = G_EARTH
@variables unit_vector(t)[1:3] = [0.0, 0.0, -sign(L0)]
@variables spring_force(t)[1:3] = [0.0, 0.0, 0.0]
@variables norm1(t) = abs(l0) spring_vel(t) = 0.0

eqs = vcat(D(pos)      ~ vel,
           D(vel)      ~ acc,
           norm1        ~ norm(pos),
           unit_vector  ~ -pos/norm1,         # direction from point mass to origin
           spring_vel   ~ -unit_vector ⋅ vel,
           spring_force ~ (c_spring * (norm1 - abs(l0)) + damping * spring_vel) * unit_vector,
           acc          ~ G_EARTH + spring_force/mass)

@named sys = ODESystem(eqs, t)
simple_sys = structural_simplify(sys)
nothing

Error & Stacktrace ⚠️

julia> include("src/Tether_02.jl")
┌ Warning: Internal error: Variable (pos(t))[1] was marked as being in 0 ~ sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - norm1(t), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/jEIdO/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[2] was marked as being in 0 ~ sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - norm1(t), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/jEIdO/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[3] was marked as being in 0 ~ sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - norm1(t), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/jEIdO/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (unit_vector(t))[1] was marked as being in 0 ~ -spring_vel(t) + (broadcast(-, unit_vector(t)))[1]*(vel(t))[1] + (broadcast(-, unit_vector(t)))[2]*(vel(t))[2] + (broadcast(-, unit_vector(t)))[3]*(vel(t))[3], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/jEIdO/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (unit_vector(t))[2] was marked as being in 0 ~ -spring_vel(t) + (broadcast(-, unit_vector(t)))[1]*(vel(t))[1] + (broadcast(-, unit_vector(t)))[2]*(vel(t))[2] + (broadcast(-, unit_vector(t)))[3]*(vel(t))[3], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/jEIdO/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (unit_vector(t))[3] was marked as being in 0 ~ -spring_vel(t) + (broadcast(-, unit_vector(t)))[1]*(vel(t))[1] + (broadcast(-, unit_vector(t)))[2]*(vel(t))[2] + (broadcast(-, unit_vector(t)))[3]*(vel(t))[3], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/jEIdO/src/structural_transformation/utils.jl:233

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

Project Tethers v0.2.0
Status `~/repos/Tethers.jl/Project.toml`
  [8f4d0f93] Conda v1.10.2
  [992eb4ea] CondaPkg v0.2.23
  [16fef848] LiveServer v1.3.1
  [961ee093] ModelingToolkit v9.28.0
  [1dea7af3] OrdinaryDiffEq v6.87.0
  [9b87118b] PackageCompiler v2.1.17
  [d96e819e] Parameters v0.12.3
  [438e738f] PyCall v1.96.4
  [d330b81b] PyPlot v2.11.5
  [21f18d07] Timers v0.1.5
  [44cfe95a] Pkg v1.10.0

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

Project Tethers v0.2.0
Status `~/repos/Tethers.jl/Manifest.toml`
  [47edcb42] ADTypes v1.6.1
  [1520ce14] AbstractTrees v0.4.5
  [7d9f7c33] Accessors v0.1.37
  [79e6a3ab] Adapt v4.0.4
  [66dad0bd] AliasTables v1.1.3
  [ec485272] ArnoldiMethod v0.4.0
  [4fba245c] ArrayInterface v7.15.0
  [4c555306] ArrayLayouts v1.10.2
  [e2ed5e7c] Bijections v0.1.7
  [d1d4a3ce] BitFlags v0.1.9
  [62783981] BitTwiddlingConvenienceFunctions v0.1.6
  [2a0fbf3d] CPUSummary v0.2.6
  [00ebfdb7] CSTParser v3.4.3
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  [944b1d66] CodecZlib v0.7.5
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  [5ae59095] Colors v0.12.11
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  [38540f10] CommonSolve v0.2.4
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  [ba0b0d4f] Krylov v0.9.6
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  [2ee39098] LabelledArrays v1.16.0
  [984bce1d] LambertW v0.4.6
  [23fbe1c1] Latexify v0.16.4
  [10f19ff3] LayoutPointers v0.1.17
  [5078a376] LazyArrays v2.1.9
  [d3d80556] LineSearches v7.2.0
  [7ed4a6bd] LinearSolve v2.31.1
  [16fef848] LiveServer v1.3.1
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  [e6f89c97] LoggingExtras v1.0.3
  [bdcacae8] LoopVectorization v0.12.171
  [6c6e2e6c] MIMEs v0.1.4
  [d8e11817] MLStyle v0.4.17
  [1914dd2f] MacroTools v0.5.13
  [d125e4d3] ManualMemory v0.1.8
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  [e1d29d7a] Missings v1.2.0
  [961ee093] ModelingToolkit v9.28.0
  [46d2c3a1] MuladdMacro v0.2.4
  [102ac46a] MultivariatePolynomials v0.5.6
  [d8a4904e] MutableArithmetics v1.4.5
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  [6fe1bfb0] OffsetArrays v1.14.1
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  [bac558e1] OrderedCollections v1.6.3
  [1dea7af3] OrdinaryDiffEq v6.87.0
  [90014a1f] PDMats v0.11.31
  [9b87118b] PackageCompiler v2.1.17
  [65ce6f38] PackageExtensionCompat v1.0.2
  [d96e819e] Parameters v0.12.3
  [69de0a69] Parsers v2.8.1
  [fa939f87] Pidfile v1.3.0
  [e409e4f3] PoissonRandom v0.4.4
  [f517fe37] Polyester v0.7.15
  [1d0040c9] PolyesterWeave v0.2.2
  [85a6dd25] PositiveFactorizations v0.2.4
  [d236fae5] PreallocationTools v0.4.23
  [aea7be01] PrecompileTools v1.2.1
  [21216c6a] Preferences v1.4.3
  [43287f4e] PtrArrays v1.2.0
  [438e738f] PyCall v1.96.4
  [d330b81b] PyPlot v2.11.5
  [1fd47b50] QuadGK v2.10.1
  [74087812] Random123 v1.7.0
  [e6cf234a] RandomNumbers v1.5.3
  [3cdcf5f2] RecipesBase v1.3.4
  [731186ca] RecursiveArrayTools v3.26.0
  [f2c3362d] RecursiveFactorization v0.2.23
  [189a3867] Reexport v1.2.2
  [05181044] RelocatableFolders v1.0.1
  [ae029012] Requires v1.3.0
  [ae5879a3] ResettableStacks v1.1.1
  [79098fc4] Rmath v0.7.1
  [7e49a35a] RuntimeGeneratedFunctions v0.5.13
  [94e857df] SIMDTypes v0.1.0
  [476501e8] SLEEFPirates v0.6.43
  [0bca4576] SciMLBase v2.48.1
  [c0aeaf25] SciMLOperators v0.3.8
  [53ae85a6] SciMLStructures v1.4.1
  [6c6a2e73] Scratch v1.2.1
  [efcf1570] Setfield v1.1.1
  [777ac1f9] SimpleBufferStream v1.1.0
  [727e6d20] SimpleNonlinearSolve v1.11.0
  [699a6c99] SimpleTraits v0.9.4
  [ce78b400] SimpleUnPack v1.1.0
  [a2af1166] SortingAlgorithms v1.2.1
  [47a9eef4] SparseDiffTools v2.19.0
  [0a514795] SparseMatrixColorings v0.3.6
  [e56a9233] Sparspak v0.3.9
  [276daf66] SpecialFunctions v2.4.0
  [aedffcd0] Static v1.1.1
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  [90137ffa] StaticArrays v1.9.7
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  [82ae8749] StatsAPI v1.7.0
  [2913bbd2] StatsBase v0.34.3
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⌅ [19f23fe9] SymbolicLimits v0.2.1
⌅ [d1185830] SymbolicUtils v2.1.2
  [0c5d862f] Symbolics v5.35.1
  [3783bdb8] TableTraits v1.0.1
  [bd369af6] Tables v1.12.0
⌅ [8ea1fca8] TermInterface v0.4.1
  [1e6cf692] TestEnv v1.102.0
  [8290d209] ThreadingUtilities v0.5.2
  [a759f4b9] TimerOutputs v0.5.24
  [21f18d07] Timers v0.1.5
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  [5c2747f8] URIs v1.5.1
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  [81def892] VersionParsing v1.3.0
  [19fa3120] VertexSafeGraphs v0.2.0
  [1d5cc7b8] IntelOpenMP_jll v2024.2.0+0
  [856f044c] MKL_jll v2024.2.0+0
  [458c3c95] OpenSSL_jll v3.0.14+0
  [efe28fd5] OpenSpecFun_jll v0.5.5+0
  [f50d1b31] Rmath_jll v0.4.2+0
  [f8abcde7] micromamba_jll v1.5.8+0
  [1317d2d5] oneTBB_jll v2021.12.0+0
  [0dad84c5] ArgTools v1.1.1
  [56f22d72] Artifacts
  [2a0f44e3] Base64
  [ade2ca70] Dates
  [8ba89e20] Distributed
  [f43a241f] Downloads v1.6.0
  [7b1f6079] FileWatching
  [9fa8497b] Future
  [b77e0a4c] InteractiveUtils
  [4af54fe1] LazyArtifacts
  [b27032c2] LibCURL v0.6.4
  [76f85450] LibGit2
  [8f399da3] Libdl
  [37e2e46d] LinearAlgebra
  [56ddb016] Logging
  [d6f4376e] Markdown
  [a63ad114] Mmap
  [ca575930] NetworkOptions v1.2.0
  [44cfe95a] Pkg v1.10.0
  [de0858da] Printf
  [3fa0cd96] REPL
  [9a3f8284] Random
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization
  [1a1011a3] SharedArrays
  [6462fe0b] Sockets
  [2f01184e] SparseArrays v1.10.0
  [10745b16] Statistics v1.10.0
  [4607b0f0] SuiteSparse
  [fa267f1f] TOML v1.0.3
  [a4e569a6] Tar v1.10.0
  [8dfed614] Test
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  [29816b5a] LibSSH2_jll v1.11.0+1
  [c8ffd9c3] MbedTLS_jll v2.28.2+1
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  [05823500] OpenLibm_jll v0.8.1+2
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  [8e850ede] nghttp2_jll v1.52.0+1
  [3f19e933] p7zip_jll v17.4.0+2

• Output of versioninfo()

Julia Version 1.10.4
Commit 48d4fd48430 (2024-06-04 10:41 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 32 × AMD Ryzen 9 7950X 16-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver3)
Threads: 16 default, 0 interactive, 9 GC (on 32 virtual cores)
Environment:
  LD_LIBRARY_PATH = /lib:/usr/lib:/usr/local/lib

Additional context

The simulation result still looks correct.

[YingboMa]

It should be

eqs = reduce(vcat, Symbolics.scalarize.(eqs));

[ufechner7]

Thanks for suggesting this workaround. But it does not help:

# Example two: Falling mass, attached to linear spring
using ModelingToolkit, OrdinaryDiffEq, LinearAlgebra
using ModelingToolkit: t_nounits as t, D_nounits as D

G_EARTH::Vector{Float64} = [0.0, 0.0, -9.81]    # gravitational acceleration     [m/s²]
L0::Float64 = -10.0                             # initial spring length      [m]

# defing the model, Z component upwards
@parameters mass=1.0 c_spring=50.0 damping=0.5 l0=L0
@variables   pos(t)[1:3] = [0.0, 0.0,  L0]
@variables   vel(t)[1:3] = [0.0, 0.0,  0.0] 
@variables   acc(t)[1:3] = G_EARTH
@variables unit_vector(t)[1:3] = [0.0, 0.0, -sign(L0)]
@variables spring_force(t)[1:3] = [0.0, 0.0, 0.0]
@variables spring_vel(t) = 0.0

eqs = vcat(D(pos)      ~ vel,
           D(vel)      ~ acc,
           unit_vector  ~ -pos/norm(pos),         # direction from point mass to origin
           spring_vel   ~ -unit_vector ⋅ vel,
           spring_force ~ (c_spring * (norm(pos) - abs(l0)) + damping * spring_vel) * unit_vector,
           acc          ~ G_EARTH + spring_force/mass)

eqs = reduce(vcat, Symbolics.scalarize.(eqs))
@named sys = ODESystem(eqs, t)
simple_sys = structural_simplify(sys)
nothing

Running this script gives even more error messages than before:

julia> include("mwes/mwe03.jl")
┌ Warning: Internal error: Variable (pos(t))[2] was marked as being in 0 ~ -(unit_vector(t))[1] + (-(pos(t))[1]) / sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[3] was marked as being in 0 ~ -(unit_vector(t))[1] + (-(pos(t))[1]) / sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[1] was marked as being in 0 ~ -(unit_vector(t))[2] + (-(pos(t))[2]) / sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[3] was marked as being in 0 ~ -(unit_vector(t))[2] + (-(pos(t))[2]) / sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[1] was marked as being in 0 ~ -(unit_vector(t))[3] + (-(pos(t))[3]) / sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[2] was marked as being in 0 ~ -(unit_vector(t))[3] + (-(pos(t))[3]) / sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[1] was marked as being in 0 ~ -(spring_force(t))[1] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[1], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[2] was marked as being in 0 ~ -(spring_force(t))[1] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[1], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[3] was marked as being in 0 ~ -(spring_force(t))[1] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[1], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[1] was marked as being in 0 ~ -(spring_force(t))[2] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[2], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[2] was marked as being in 0 ~ -(spring_force(t))[2] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[2], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[3] was marked as being in 0 ~ -(spring_force(t))[2] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[2], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[1] was marked as being in 0 ~ -(spring_force(t))[3] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[3], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[2] was marked as being in 0 ~ -(spring_force(t))[3] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[3], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233
┌ Warning: Internal error: Variable (pos(t))[3] was marked as being in 0 ~ -(spring_force(t))[3] + (c_spring*(sqrt(Symbolics._mapreduce(#396, +, pos(t), Colon(), (:init => false,))) - abs(l0)) + damping*spring_vel(t))*(unit_vector(t))[3], but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/GyyTb/src/structural_transformation/utils.jl:233

I am now using ModelingToolkit v9.30.1.

Can you please re-open this issue?

[YingboMa]

eqs = Symbolics.scalarize.(reduce(vcat, Symbolics.scalarize.(eqs))) will work.