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Use stiff solver in DEIM test #164

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Merged
ChrisRackauckas merged 2 commits into from
Jul 12, 2026
Merged

Use stiff solver in DEIM test #164

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3a746c2
Use stiff solver in DEIM test
ChrisRackauckas Jul 12, 2026
0e4059c
Fix DEIM test init: supply consistent u0 instead of missing-guess hack
ChrisRackauckas Jul 12, 2026
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13 changes: 7 additions & 6 deletions test/deim.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -38,11 +38,12 @@ order = 2
discretization = MOLFiniteDifference(dxs, t; approx_order = order)
ode_sys, tspan = symbolic_discretize(pde_sys, discretization)
simp_sys = mtkcompile(ode_sys) # field substitutions is non-empty
ode_prob = ODEProblem(
simp_sys, nothing, tspan;
missing_guess_value = ModelingToolkit.MissingGuessValue.Constant(0.0)
)
sol = solve(ode_prob, Tsit5(), saveat = 1.0)
# The BCs fix every state to 0 at t=0, so provide those initial values directly.
# Leaving them as missing guesses makes MethodOfLines' initialization system
# structurally singular under MTK v11, and the least-squares solve diverges.
u0 = [u => 0.0 for u in ModelingToolkit.get_unknowns(simp_sys)]
ode_prob = ODEProblem(simp_sys, u0, tspan)
sol = solve(ode_prob, Rodas5P(), saveat = 1.0)

snapshot_simpsys = Array(sol.original_sol)
pod_dim = 3
Expand All @@ -53,7 +54,7 @@ deim_sys = @test_nowarn deim(simp_sys, snapshot_simpsys, pod_dim)

deim_prob = ODEProblem(complete(deim_sys), nothing, tspan)

deim_sol = solve(deim_prob, Tsit5(), saveat = 1.0)
deim_sol = solve(deim_prob, Rodas5P(), saveat = 1.0)

nₓ = length(sol[x])
nₜ = length(sol[t])
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