docs: add comments explaining why remake is called in the problem constructor

Author: AayushSabharwal

src/systems/diffeqs/abstractodesystem.jl

@@ -759,6 +759,7 @@ function DiffEqBase.ODEProblem{iip, specialize}(sys::AbstractODESystem, u0map =
         kwargs1 = merge(kwargs1, (; tstops))
     end
 
+    # Call `remake` so it runs initialization if it is trivial
     return remake(ODEProblem{iip}(f, u0, tspan, p, pt; kwargs1..., kwargs...))
 end
 get_callback(prob::ODEProblem) = prob.kwargs[:callback]
@@ -963,6 +964,7 @@ function DiffEqBase.DAEProblem{iip}(sys::AbstractODESystem, du0map, u0map, tspan
         kwargs1 = merge(kwargs1, (; tstops))
     end
 
+    # Call `remake` so it runs initialization if it is trivial
     return remake(DAEProblem{iip}(
         f, du0, u0, tspan, p; differential_vars = differential_vars,
         kwargs..., kwargs1...))
@@ -1009,6 +1011,7 @@ function DiffEqBase.DDEProblem{iip}(sys::AbstractODESystem, u0map = [],
     if cbs !== nothing
         kwargs1 = merge(kwargs1, (callback = cbs,))
     end
+    # Call `remake` so it runs initialization if it is trivial
     return remake(DDEProblem{iip}(f, u0, h, tspan, p; kwargs1..., kwargs...))
 end
 
@@ -1058,6 +1061,7 @@ function DiffEqBase.SDDEProblem{iip}(sys::AbstractODESystem, u0map = [],
     else
         noise_rate_prototype = zeros(eltype(u0), size(noiseeqs))
     end
+    # Call `remake` so it runs initialization if it is trivial
     return remake(SDDEProblem{iip}(f, f.g, u0, h, tspan, p;
         noise_rate_prototype =
         noise_rate_prototype, kwargs1..., kwargs...))

src/systems/diffeqs/sdesystem.jl

@@ -792,6 +792,7 @@ function DiffEqBase.SDEProblem{iip, specialize}(
 
     kwargs = filter_kwargs(kwargs)
 
+    # Call `remake` so it runs initialization if it is trivial
     return remake(SDEProblem{iip}(f, u0, tspan, p; callback = cbs, noise,
         noise_rate_prototype = noise_rate_prototype, kwargs...))
 end

src/systems/nonlinear/nonlinearsystem.jl

@@ -526,6 +526,7 @@ function DiffEqBase.NonlinearProblem{iip}(sys::NonlinearSystem, u0map,
     f, u0, p = process_SciMLProblem(NonlinearFunction{iip}, sys, u0map, parammap;
         check_length, kwargs...)
     pt = something(get_metadata(sys), StandardNonlinearProblem())
+    # Call `remake` so it runs initialization if it is trivial
     return remake(NonlinearProblem{iip}(f, u0, p, pt; filter_kwargs(kwargs)...))
 end
 
@@ -555,6 +556,7 @@ function DiffEqBase.NonlinearLeastSquaresProblem{iip}(sys::NonlinearSystem, u0ma
     f, u0, p = process_SciMLProblem(NonlinearFunction{iip}, sys, u0map, parammap;
         check_length, kwargs...)
     pt = something(get_metadata(sys), StandardNonlinearProblem())
+    # Call `remake` so it runs initialization if it is trivial
     return remake(NonlinearLeastSquaresProblem{iip}(f, u0, p; filter_kwargs(kwargs)...))
 end