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Adding backup solver Rodas5Pr if no states in model #37

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Merged
AnHeuermann merged 1 commit into from
Mar 26, 2026
Merged

Adding backup solver Rodas5Pr if no states in model #37

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31 changes: 14 additions & 17 deletions src/simulate.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -78,28 +78,25 @@ function run_simulate(ode_prob,
# Redirect all library log output (including Symbolics/MTK warnings)
# to the log file so they don't clutter stdout.
sol = Logging.with_logger(logger) do
# Overwrite saveat, always use dense output.
# For stateless models (no unknowns) the adaptive solver takes no
# internal steps and sol.t would be empty with saveat=[].
# Supply explicit time points so observed variables can be evaluated.
# Special handling for systems without states
sys = ode_prob.f.sys
n_unknowns = length(ModelingToolkit.unknowns(sys))

kwargs = if n_unknowns == 0
# No unknowns at all (e.g. BusUsage):
# Supply explicit time points so observed variables can be evaluated.
eqs = ModelingToolkit.equations(sys)
n_states = count(ModelingToolkitBase.isdiffeq, eqs)
kwargs, active_solver = if n_states == 0
# No state variables (e.g. BusUsage, Modelica.Electrical.Analog.Examples.OpAmps.Subtracter):
# Use Rodas5Pr on a fixed grid so observed variables can be evaluated at each step.
dt_s = (ode_prob.tspan[end] - ode_prob.tspan[1]) / (settings.saveat_n - 1)
saveat_s = collect(range(ode_prob.tspan[1], ode_prob.tspan[end]; length = settings.saveat_n))
(saveat = saveat_s, dense = true)
(saveat = saveat_s, dt = dt_s, adaptive = false, dense = false),
DifferentialEquations.Rodas5Pr()
else
(saveat = Float64[], dense = true)
saveat_s = Float64[]
(saveat = saveat_s, dense = true), solver
end

# Log solver settings — init returns NullODEIntegrator (no .opts)
# when the problem has no unknowns (u::Nothing), so only inspect
# opts when a real integrator is returned.
# Use our own `saveat` vector for the log: integ.opts.saveat is a
# BinaryHeap which does not support iterate/minimum/maximum.
integ = DifferentialEquations.init(ode_prob, solver; kwargs...)
# Log solver settings
integ = DifferentialEquations.init(ode_prob, active_solver; kwargs...)
saveat_s = kwargs.saveat
solver_settings_string = if hasproperty(integ, :opts)
sv_str = isempty(saveat_s) ? "[]" : "$(length(saveat_s)) points in [$(first(saveat_s)), $(last(saveat_s))]"
Expand All @@ -119,7 +116,7 @@ function run_simulate(ode_prob,
end

# Solve
DifferentialEquations.solve(ode_prob, solver; kwargs...)
DifferentialEquations.solve(ode_prob, active_solver; kwargs...)
end
sim_time = time() - t0
if sol.retcode == DifferentialEquations.ReturnCode.Success
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