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Fix dual type promotion in remake with dummy derivatives #3337

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Merged
merged 4 commits into from
Jan 18, 2025
Merged

Fix dual type promotion in remake with dummy derivatives #3337

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55e607b
Substitute dummy derivatives in initialization problem
hersle Jan 17, 2025
94ff612
Add test
hersle Jan 17, 2025
f5937ae
Use schedule to replace dummy derivatives
hersle Jan 17, 2025
60e4723
Format
hersle Jan 17, 2025
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1 change: 1 addition & 0 deletions src/systems/diffeqs/abstractodesystem.jl
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Expand Up @@ -1366,6 +1366,7 @@ function InitializationProblem{iip, specialize}(sys::AbstractSystem,
end

u0map = merge(ModelingToolkit.guesses(sys), todict(guesses), todict(u0map))
u0map = Dict(diff2term(var) => val for (var, val) in u0map) # replace D(x) -> x_t etc.
fullmap = merge(u0map, parammap)
u0T = Union{}
for sym in unknowns(isys)
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20 changes: 20 additions & 0 deletions test/extensions/ad.jl
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Expand Up @@ -4,6 +4,7 @@ using Zygote
using SymbolicIndexingInterface
using SciMLStructures
using OrdinaryDiffEq
using NonlinearSolve
using SciMLSensitivity
using ForwardDiff
using ChainRulesCore
Expand Down Expand Up @@ -103,3 +104,22 @@ vals = (1.0f0, 3ones(Float32, 3))
tangent = rand_tangent(ps)
fwd, back = ChainRulesCore.rrule(remake_buffer, sys, ps, idxs, vals)
@inferred back(tangent)

@testset "Dual type promotion in remake with dummy derivatives" begin # https://github.com/SciML/ModelingToolkit.jl/issues/3336
# Throw ball straight up into the air
@variables y(t)
eqs = [D(D(y)) ~ -9.81]
initialization_eqs = [y^2 ~ 0] # initialize y = 0 in a way that builds an initialization problem
@named sys = ODESystem(eqs, t; initialization_eqs)
sys = structural_simplify(sys)

# Find initial throw velocity that reaches exactly 10 m after 1 s
dprob0 = ODEProblem(sys, [D(y) => NaN], (0.0, 1.0), []; guesses = [y => 0.0])
nprob = NonlinearProblem((ics, _) -> begin
dprob = remake(dprob0, u0 = Dict(D(y) => ics[1]))
dsol = solve(dprob, Tsit5())
return [dsol[y][end] - 10.0]
end, [1.0])
nsol = solve(nprob, NewtonRaphson())
@test nsol[1] ≈ 10.0/1.0 + 9.81*1.0/2 # anal free fall solution is y = v0*t - g*t^2/2 -> v0 = y/t + g*t/2
end
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