feat: add lazy initialization to remake

Author: AayushSabharwal

src/initialization.jl

@@ -225,3 +225,15 @@ function get_initial_values(prob, valp, f, alg::OverrideInit,
 
     return u0, p, success
 end
+
+function is_trivial_initialization(initdata::OverrideInitData)
+    state_values(initdata.initializeprob) === nothing
+end
+
+function is_trivial_initialization(f::AbstractSciMLFunction)
+    has_initialization_data(f) && is_trivial_initialization(f.initialization_data)
+end
+
+function is_trivial_initialization(prob::AbstractSciMLProblem)
+    is_trivial_initialization(prob.f)
+end

src/remake.jl

@@ -114,6 +114,7 @@ function remake(prob::ODEProblem; f = missing,
         interpret_symbolicmap = true,
         build_initializeprob = true,
         use_defaults = false,
+        lazy_initialization = nothing,
         _kwargs...)
     if tspan === missing
         tspan = prob.tspan
@@ -123,6 +124,8 @@ function remake(prob::ODEProblem; f = missing,
 
     iip = isinplace(prob)
 
+    initialization_data = prob.f.initialization_data
+
     if f === missing
         if build_initializeprob
             initialization_data = remake_initialization_data_compat_wrapper(
@@ -170,13 +173,25 @@ function remake(prob::ODEProblem; f = missing,
         _f = ODEFunction{isinplace(prob), specialization(prob.f)}(f)
     end
 
-    if kwargs === missing
+    prob = if kwargs === missing
         ODEProblem{isinplace(prob)}(
             _f, newu0, tspan, newp, prob.problem_type; prob.kwargs...,
             _kwargs...)
     else
         ODEProblem{isinplace(prob)}(_f, newu0, tspan, newp, prob.problem_type; kwargs...)
     end
+
+    if lazy_initialization === nothing
+        lazy_initialization = !is_trivial_initialization(initialization_data)
+    end
+    if !lazy_initialization
+        u0, p, _ = get_initial_values(
+            prob, prob, prob.f, OverrideInit(), Val(isinplace(prob)))
+        @reset prob.u0 = u0
+        @reset prob.p = p
+    end
+
+    return prob
 end
 
 """

test/downstream/modelingtoolkit_remake.jl

@@ -336,3 +336,12 @@ end
     @test sccprob4.parameter_object !== sccprob4.probs[1].p
     @test sccprob4.parameter_object !== sccprob4.probs[2].p
 end
+
+@testset "Lazy initialization" begin
+    @variables x(t) [guess = 1.0] y(t) [guess = 1.0]
+    @parameters p=missing [guess = 1.0]
+    @mtkbuild sys = ODESystem([D(x) ~ x, x + y ~ p], t)
+    prob = ODEProblem(sys, [x => 1.0, y => 1.0], (0.0, 1.0))
+    prob2 = remake(prob; u0 = [x => 2.0])
+    @test prob2.ps[p] ≈ 3.0
+end