Merge pull request #3495 from vyudu/document_DAE

docs: Document DAEProblem constructor

Author: ChrisRackauckas

docs/src/systems/ODESystem.md

@@ -62,6 +62,7 @@ jacobian_sparsity
 ODEFunction(sys::ModelingToolkit.AbstractODESystem, args...)
 ODEProblem(sys::ModelingToolkit.AbstractODESystem, args...)
 SteadyStateProblem(sys::ModelingToolkit.AbstractODESystem, args...)
+DAEProblem(sys::ModelingToolkit.AbstractODESystem, args...)
 ```
 
 ## Expression Constructors

src/systems/diffeqs/abstractodesystem.jl

@@ -941,6 +941,10 @@ DiffEqBase.DAEProblem{iip}(sys::AbstractODESystem, du0map, u0map, tspan,
 
 Generates a DAEProblem from an ODESystem and allows for automatically
 symbolically calculating numerical enhancements.
+
+Note: Solvers for DAEProblems like DFBDF, DImplicitEuler, DABDF2 are 
+generally slower than the ones for ODEProblems. We recommend trying 
+ODEProblem and its solvers for your problem first.
 """
 function DiffEqBase.DAEProblem(sys::AbstractODESystem, args...; kwargs...)
     DAEProblem{true}(sys, args...; kwargs...)
@@ -951,7 +955,7 @@ function DiffEqBase.DAEProblem{iip}(sys::AbstractODESystem, du0map, u0map, tspan
         warn_initialize_determined = true,
         check_length = true, eval_expression = false, eval_module = @__MODULE__, kwargs...) where {iip}
     if !iscomplete(sys)
-        error("A completed system is required. Call `complete` or `structural_simplify` on the system before creating a `DAEProblem`")
+        error("A completed system is required. Call `complete` or `structural_simplify` on the system before creating a `DAEProblem`.")
     end
     f, du0, u0, p = process_SciMLProblem(DAEFunction{iip}, sys, u0map, parammap;
         implicit_dae = true, du0map = du0map, check_length,