allow building coupled odes even if prob doesn't have tspan

Author: Datseris

CHANGELOG.md

@@ -12,8 +12,6 @@ See also the online overarching tutorial for an example.
 
 At the moment this is only possible for `CoupledODEs` and its derivative systems, as these are the only systems that can be made by a `DEProblem`, however it should be easy to allow e.g., `DeterministicIterated` to be created by a `DiscreteProblem`.
 
-The integration is supported by the functions `current_parameter`, `set_parameter!` where a symbolic MTK parameter can be given as an index. In `observe_state`, a state variable or observed variable symbol can be given.
-
 Also:
 
 - Crucial bugfix for `successful_step` that was not working properly for discrete time systems.

Project.toml

@@ -1,7 +1,7 @@
 name = "DynamicalSystemsBase"
 uuid = "6e36e845-645a-534a-86f2-f5d4aa5a06b4"
 repo = "https://github.com/JuliaDynamics/DynamicalSystemsBase.jl.git"
-version = "3.5.0"
+version = "3.5.1"
 
 [deps]
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"

src/core_systems/continuous_time_ode.jl

@@ -96,6 +96,11 @@ function CoupledODEs(prob::ODEProblem, diffeq = DEFAULT_DIFFEQ; special_kwargs..
     IIP = isinplace(prob)
     D = length(prob.u0)
     P = typeof(prob.p)
+    if prob.tspan === (nothing, nothing)
+        # If the problem was made via MTK, it is possible to not have a default timespan.
+        U = eltype(prob.u0)
+        prob = SciMLBase.remake(prob; tspan = (U(0), U(Inf)))
+    end
     solver, remaining = _decompose_into_solver_and_remaining(diffeq)
     integ = __init(prob, solver; remaining..., special_kwargs...,
         # Integrators are used exclusively iteratively. There is no reason to save anything.

test/mtk_integration.jl

@@ -108,4 +108,34 @@ set_parameter!(ds, 1, 2.0)
 
 @test observe_state(ds, 1) == 1.0
 
-@test_throws ArgumentError observe_state(ds, fol_1.f)
+@test_throws ArgumentError observe_state(ds, fol_1.f)
+
+# Test that remake works also without anything initial
+
+@variables t
+D = Differential(t)
+@mtkmodel Roessler begin
+    @parameters begin
+        a = 0.2
+        b = 0.2
+        c = 5.7
+    end
+    @variables begin
+        x(t) = 1.0
+        y(t) = 0.0
+        z(t) = 0.0
+        nlt(t) # nonlinear term
+    end
+    @equations begin
+        D(x) ~ -y -z
+        D(y) ~ x + a*y
+        D(z) ~ b + nlt
+        nlt ~ z*(x - c)
+    end
+end
+
+@mtkbuild roessler_model = Roessler()
+prob = ODEProblem(roessler_model)
+roessler = CoupledODEs(prob)
+
+@test roessler isa CoupledODEs