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fix: improve reference calculation for DiffCache #63

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Merged
AayushSabharwal merged 2 commits into from
Apr 1, 2026
Merged

fix: improve reference calculation for DiffCache #63

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7792798
fix: improve reference calculation for `DiffCache`
AayushSabharwal Apr 1, 2026
1dab2bc
test: test AD through inline linear SCC DiffCache
AayushSabharwal Apr 1, 2026
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4 changes: 3 additions & 1 deletion lib/ModelingToolkitTearing/Project.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ UUIDs = "cf7118a7-6976-5b1a-9a39-7adc72f591a4"
BipartiteGraphs = "0.1.3"
CommonSolve = "0.2"
DocStringExtensions = "0.7, 0.8, 0.9"
ForwardDiff = "1.3"
Graphs = "1"
LinearAlgebra = "1"
ModelingToolkit = "11"
Expand All @@ -44,8 +45,9 @@ UUIDs = "1"
julia = "1.10"

[extras]
ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

[targets]
test = ["Test", "ModelingToolkit"]
test = ["Test", "ModelingToolkit", "ForwardDiff"]
4 changes: 4 additions & 0 deletions lib/ModelingToolkitTearing/src/reassemble.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -606,6 +606,10 @@ function get_linear_scc_linsol(state::TearingState, alg_eqs::Vector{Int},
else
reference = fullvars[state_idx]
end
reference = Symbolics.STerm(
promote, Symbolics.SArgsT((reference, MTKBase.get_iv(sys)::SymbolicT));
type = Vector{Real}, shape = [1:2]
)[1]
sys, A_cache = MTKBase.add_diffcache(sys, length(A))
A_allocator = A_cache(reference)
A = SU.Code.with_allocator(A_allocator, SU.Const{VartypeT}(A))
Expand Down
28 changes: 28 additions & 0 deletions lib/ModelingToolkitTearing/test/runtests.jl
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Expand Up @@ -8,6 +8,7 @@ using Graphs
import StateSelection
using ModelingToolkit: t_nounits as t, D_nounits as D
import SymbolicUtils as SU
using ForwardDiff

@testset "`InferredDiscrete` validation" begin
k = ShiftIndex()
Expand Down Expand Up @@ -110,3 +111,30 @@ end
@test isempty(unknowns(sys))
@test length(observed(sys)) == 2
end

@testset "Duals through inline linear SCC DiffCaches" begin
@variables x(t) y(t) z(t) w(t) q(t)
reassemble_alg = MTKTearing.DefaultReassembleAlgorithm(; inline_linear_sccs = true)
@mtkcompile sys = System(
[
D(x) ~ 2t + 1,
t * y + x * z + w ~ 4,
4y + 3z + 2w ~ 7,
2x * y + 3t * z + w ~ 10,
D(q) ~ 2w,
],
t
) reassemble_alg = reassemble_alg

prob = ODEProblem(sys, [x => 1, q => 1], (0.0, 1.0); guesses = [x => 1, y => 1, z => 1, w => 1, q => 1])

buffer = similar(prob.u0)
@test_nowarn ForwardDiff.jacobian(buffer, prob.u0) do du, u
@test eltype(u) <: ForwardDiff.Dual
prob.f.f.f_iip(du, u, prob.p, 1.0)
end
@test_nowarn ForwardDiff.derivative(buffer, 1.2) do du, t
@test t isa ForwardDiff.Dual
prob.f.f.f_iip(du, prob.u0, prob.p, t)
end
end
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