ModelingToolkit.jl
ModelingToolkit.jl copied to clipboard
SciML
What does "variable was actually zero" internal error mean when using ifelse?
I am using ifelse in an ODE like this:
using ModelingToolkit, OrdinaryDiffEq
using ModelingToolkit: t_nounits as t, D_nounits as D
@variables x(t) # position
eqs = [D(D(x)) ~ ifelse(x < 5, 1, 0)] # accelerate for first 5 meters
ics = [x ~ 0, D(x) ~ 0]
@named sys = ODESystem(eqs, t; initialization_eqs = ics)
ssys = mtkcompile(sys)
prob = ODEProblem(ssys, [], (0.0, 10.0))
sol = solve(prob, Tsit5())
The call to mtkcompile(sys) warns
┌ Warning: Internal error: Variable x(t) was marked as being in Differential(t)(Differential(t)(x(t))) ~ ifelse(x(t) < 5, 1, 0), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ~/.julia/packages/ModelingToolkit/OViQH/src/structural_transformation/utils.jl:292
What does this mean? Should I worry about it?
The solution looks fine to me. Apologies if I am overlooking something trivial!
The problem still exists in MTK v10.21. It would be great to get an answer if the maintainers are aware of it.
The bug 🐞
Model compilation throws "Internal error" warnings when ifelse() is used in an equation.
⚠️ This can prevent the compilation of larger systems where a lot of equations contain ifelse() due to the large number of warnings printed. ⚠️
Expected behavior
No warning should be triggered during compilation.
Minimal Reproducible Example 👇
using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@mtkmodel InternalError begin
@variables begin
x(t) = 0.0
end
@equations begin
D(x) ~ ifelse(x < 5, 1, 0)
end
end
@mtkcompile sys = InternalError()
Warning ⚠️
┌ Warning: Internal error: Variable x(t) was marked as being in Differential(t)(x(t)) ~ ifelse(x(t) < 5, 1, 0), but was actually zero
└ @ ModelingToolkit.StructuralTransformations ..\.julia\packages\ModelingToolkit\hlGut\src\structural_transformation\utils.jl:292
Environment
- Output of
using Pkg; Pkg.status()
Status `...\Project.toml`
[961ee093] ModelingToolkit v10.21.0
- Output of
using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)
Status `...\Manifest.toml`
[47edcb42] ADTypes v1.17.0
[1520ce14] AbstractTrees v0.4.5
[7d9f7c33] Accessors v0.1.42
[79e6a3ab] Adapt v4.3.0
[66dad0bd] AliasTables v1.1.3
[ec485272] ArnoldiMethod v0.4.0
[4fba245c] ArrayInterface v7.20.0
[4c555306] ArrayLayouts v1.11.2
[e2ed5e7c] Bijections v0.2.2
[62783981] BitTwiddlingConvenienceFunctions v0.1.6
[8e7c35d0] BlockArrays v1.7.2
[70df07ce] BracketingNonlinearSolve v1.3.0
[2a0fbf3d] CPUSummary v0.2.7
[d360d2e6] ChainRulesCore v1.26.0
[fb6a15b2] CloseOpenIntervals v0.1.13
⌅ [861a8166] Combinatorics v1.0.2
[a80b9123] CommonMark v0.9.1
[38540f10] CommonSolve v0.2.4
[bbf7d656] CommonSubexpressions v0.3.1
[f70d9fcc] CommonWorldInvalidations v1.0.0
[34da2185] Compat v4.18.0
[b152e2b5] CompositeTypes v0.1.4
[a33af91c] CompositionsBase v0.1.2
[2569d6c7] ConcreteStructs v0.2.3
[187b0558] ConstructionBase v1.6.0
[adafc99b] CpuId v0.3.1
[9a962f9c] DataAPI v1.16.0
⌅ [864edb3b] DataStructures v0.18.22
[2b5f629d] DiffEqBase v6.188.0
[459566f4] DiffEqCallbacks v4.9.0
[77a26b50] DiffEqNoiseProcess v5.24.1
[163ba53b] DiffResults v1.1.0
[b552c78f] DiffRules v1.15.1
[a0c0ee7d] DifferentiationInterface v0.7.7
[8d63f2c5] DispatchDoctor v0.4.26
[31c24e10] Distributions v0.25.120
[ffbed154] DocStringExtensions v0.9.5
[5b8099bc] DomainSets v0.7.16
[7c1d4256] DynamicPolynomials v0.6.3
[06fc5a27] DynamicQuantities v1.8.0
[4e289a0a] EnumX v1.0.5
[f151be2c] EnzymeCore v0.8.13
[e2ba6199] ExprTools v0.1.10
[55351af7] ExproniconLite v0.10.14
[7034ab61] FastBroadcast v0.3.5
[9aa1b823] FastClosures v0.3.2
[a4df4552] FastPower v1.1.3
[1a297f60] FillArrays v1.13.0
[64ca27bc] FindFirstFunctions v1.4.1
[6a86dc24] FiniteDiff v2.28.1
[1fa38f19] Format v1.3.7
[f6369f11] ForwardDiff v1.1.0
[069b7b12] FunctionWrappers v1.1.3
[77dc65aa] FunctionWrappersWrappers v0.1.3
[d9f16b24] Functors v0.5.2
[46192b85] GPUArraysCore v0.2.0
[c27321d9] Glob v1.3.1
[86223c79] Graphs v1.13.1
[34004b35] HypergeometricFunctions v0.3.28
[615f187c] IfElse v0.1.1
[3263718b] ImplicitDiscreteSolve v1.2.0
[d25df0c9] Inflate v0.1.5
[18e54dd8] IntegerMathUtils v0.1.3
[8197267c] IntervalSets v0.7.11
[3587e190] InverseFunctions v0.1.17
[92d709cd] IrrationalConstants v0.2.4
[82899510] IteratorInterfaceExtensions v1.0.0
[692b3bcd] JLLWrappers v1.7.1
[ae98c720] Jieko v0.2.1
[98e50ef6] JuliaFormatter v2.1.6
⌅ [70703baa] JuliaSyntax v0.4.10
[ccbc3e58] JumpProcesses v9.17.0
[b964fa9f] LaTeXStrings v1.4.0
[23fbe1c1] Latexify v0.16.10
[10f19ff3] LayoutPointers v0.1.17
[87fe0de2] LineSearch v0.1.4
[d3d80556] LineSearches v7.4.0
[2ab3a3ac] LogExpFunctions v0.3.29
[d8e11817] MLStyle v0.4.17
[1914dd2f] MacroTools v0.5.16
[d125e4d3] ManualMemory v0.1.8
[bb5d69b7] MaybeInplace v0.1.4
[e1d29d7a] Missings v1.2.0
[961ee093] ModelingToolkit v10.21.0
[2e0e35c7] Moshi v0.3.7
[46d2c3a1] MuladdMacro v0.2.4
⌃ [102ac46a] MultivariatePolynomials v0.5.9
[d8a4904e] MutableArithmetics v1.6.4
[d41bc354] NLSolversBase v7.10.0
[77ba4419] NaNMath v1.1.3
[be0214bd] NonlinearSolveBase v1.14.0
[6fe1bfb0] OffsetArrays v1.17.0
[429524aa] Optim v1.13.2
[bac558e1] OrderedCollections v1.8.1
[bbf590c4] OrdinaryDiffEqCore v1.33.0
[90014a1f] PDMats v0.11.35
[d96e819e] Parameters v0.12.3
[e409e4f3] PoissonRandom v0.4.6
[f517fe37] Polyester v0.7.18
[1d0040c9] PolyesterWeave v0.2.2
[85a6dd25] PositiveFactorizations v0.2.4
[d236fae5] PreallocationTools v0.4.34
⌅ [aea7be01] PrecompileTools v1.2.1
[21216c6a] Preferences v1.5.0
[27ebfcd6] Primes v0.5.7
[43287f4e] PtrArrays v1.3.0
[1fd47b50] QuadGK v2.11.2
[74087812] Random123 v1.7.1
[e6cf234a] RandomNumbers v1.6.0
[3cdcf5f2] RecipesBase v1.3.4
[731186ca] RecursiveArrayTools v3.37.1
[189a3867] Reexport v1.2.2
[ae029012] Requires v1.3.1
[ae5879a3] ResettableStacks v1.1.1
[79098fc4] Rmath v0.8.0
[7e49a35a] RuntimeGeneratedFunctions v0.5.15
[9dfe8606] SCCNonlinearSolve v1.4.0
[94e857df] SIMDTypes v0.1.0
[0bca4576] SciMLBase v2.117.1
[19f34311] SciMLJacobianOperators v0.1.11
[c0aeaf25] SciMLOperators v1.7.1
[431bcebd] SciMLPublic v1.0.0
[53ae85a6] SciMLStructures v1.7.0
[efcf1570] Setfield v1.1.2
[727e6d20] SimpleNonlinearSolve v2.7.0
[699a6c99] SimpleTraits v0.9.5
[ce78b400] SimpleUnPack v1.1.0
[a2af1166] SortingAlgorithms v1.2.2
[276daf66] SpecialFunctions v2.5.1
[aedffcd0] Static v1.2.0
[0d7ed370] StaticArrayInterface v1.8.0
[90137ffa] StaticArrays v1.9.15
[1e83bf80] StaticArraysCore v1.4.3
[10745b16] Statistics v1.11.1
[82ae8749] StatsAPI v1.7.1
[2913bbd2] StatsBase v0.34.6
[4c63d2b9] StatsFuns v1.5.0
[7792a7ef] StrideArraysCore v0.5.8
[2efcf032] SymbolicIndexingInterface v0.3.43
[19f23fe9] SymbolicLimits v0.2.2
[d1185830] SymbolicUtils v3.32.0
[0c5d862f] Symbolics v6.54.0
[ed4db957] TaskLocalValues v0.1.3
[8ea1fca8] TermInterface v2.0.0
[1c621080] TestItems v1.0.0
[8290d209] ThreadingUtilities v0.5.5
[a759f4b9] TimerOutputs v0.5.29
[410a4b4d] Tricks v0.1.12
[781d530d] TruncatedStacktraces v1.4.0
[5c2747f8] URIs v1.6.1
[3a884ed6] UnPack v1.0.2
[1986cc42] Unitful v1.24.0
[a7c27f48] Unityper v0.1.6
[61579ee1] Ghostscript_jll v9.55.1+0
[aacddb02] JpegTurbo_jll v3.1.3+0
[efe28fd5] OpenSpecFun_jll v0.5.6+0
[f50d1b31] Rmath_jll v0.5.1+0
[56f22d72] Artifacts v1.11.0
[2a0f44e3] Base64 v1.11.0
[ade2ca70] Dates v1.11.0
[8ba89e20] Distributed v1.11.0
[9fa8497b] Future v1.11.0
[b77e0a4c] InteractiveUtils 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
[de0858da] Printf 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
[4607b0f0] SuiteSparse
[fa267f1f] TOML v1.0.3
[8dfed614] Test v1.11.0
[cf7118a7] UUIDs v1.11.0
[4ec0a83e] Unicode v1.11.0
[e66e0078] CompilerSupportLibraries_jll v1.1.1+0
[4536629a] OpenBLAS_jll v0.3.27+1
[05823500] OpenLibm_jll v0.8.5+0
[bea87d4a] SuiteSparse_jll v7.7.0+0
[83775a58] Zlib_jll v1.2.13+1
[8e850b90] libblastrampoline_jll v5.11.0+0
- Output of
versioninfo()
Julia Version 1.11.6
Commit 9615af0f26 (2025-07-09 12:58 UTC)
Build Info:
Official https://julialang.org/ release
Platform Info:
OS: Windows (x86_64-w64-mingw32)
WORD_SIZE: 64
LLVM: libLLVM-16.0.6 (ORCJIT, alderlake)
Threads: 1 default, 0 interactive, 1 GC
Environment:
JULIA_EDITOR = code
JULIA_VSCODE_REPL = 1
JULIA_NUM_THREADS = 0
That seems like a misfire. It should assign to that equation since it's D(x) so assigning x to that equation is fine. ifelse(x<5,1,0) then has variable incidence, where you cannot assign x to it if it's an algebraic equation since x is not actually in the equation, i.e. it has zero incidence for every value of x. But that would only matter if it's an algebraic equation, which it's not, so the assignment of x is correct.
