From 86364205fee9c253be69c479b156a818720acea4 Mon Sep 17 00:00:00 2001
From: Isaac Wheeler <ickaser@gmail.com>
Date: Tue, 3 Dec 2024 14:22:21 +0100
Subject: [PATCH 1/2] Make CheckInit more informative

---
 src/SciMLBase.jl      |  2 ++
 src/initialization.jl | 12 +++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/SciMLBase.jl b/src/SciMLBase.jl
index 5cbc1b4a8..99495d93f 100644
--- a/src/SciMLBase.jl
+++ b/src/SciMLBase.jl
@@ -835,6 +835,8 @@ export ODEFunction, DiscreteFunction, ImplicitDiscreteFunction, SplitFunction, D
 
 export OptimizationFunction, MultiObjectiveOptimizationFunction
 
+export CheckInit
+
 export EnsembleThreads, EnsembleDistributed, EnsembleSplitThreads, EnsembleSerial
 
 export EnsembleAnalysis, EnsembleSummary
diff --git a/src/initialization.jl b/src/initialization.jl
index 4e976e168..92125fa32 100644
--- a/src/initialization.jl
+++ b/src/initialization.jl
@@ -59,7 +59,17 @@ end
 
 function Base.showerror(io::IO, e::CheckInitFailureError)
     print(io,
-        "CheckInit specified but initialization not satisfied. normresid = $(e.normresid) > abstol = $(e.abstol)")
+        "DAE initialization failed: your u0 did not satisfy the initialization requirements, 
+        normresid = $(e.normresid) > abstol = $(e.abstol). If you wish for the system to 
+        automatically change the algebraic variables to satisfy the algebraic constraints, 
+        please pass `initializealg = BrownBasicInit()` to solve (this option will require 
+        `using OrdinaryDiffEqNonlinearSolve`). If you wish to perform an initialization on the
+        complete u0, please pass initializealg = ShampineCollocationInit() to solve. Note that 
+        initialization can be a very difficult process for DAEs and in many cases can be 
+        numerically intractable without symbolic manipulation of the system. For an automated 
+        system that will generate numerically stable initializations, see ModelingToolkit.jl 
+        structural simplification for more details."
+    )
 end
 
 struct OverrideInitMissingAlgorithm <: Exception end

From 3ae7b69515cfff8d8f29a955a389cbbd9beed767 Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Tue, 3 Dec 2024 07:38:40 -0700
Subject: [PATCH 2/2] Update initialization.jl

---
 src/initialization.jl | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/src/initialization.jl b/src/initialization.jl
index 92125fa32..acf714c58 100644
--- a/src/initialization.jl
+++ b/src/initialization.jl
@@ -55,21 +55,27 @@ function get_initial_values end
 struct CheckInitFailureError <: Exception
     normresid::Any
     abstol::Any
+    isdae::Bool
 end
 
 function Base.showerror(io::IO, e::CheckInitFailureError)
     print(io,
         "DAE initialization failed: your u0 did not satisfy the initialization requirements, 
-        normresid = $(e.normresid) > abstol = $(e.abstol). If you wish for the system to 
-        automatically change the algebraic variables to satisfy the algebraic constraints, 
-        please pass `initializealg = BrownBasicInit()` to solve (this option will require 
-        `using OrdinaryDiffEqNonlinearSolve`). If you wish to perform an initialization on the
-        complete u0, please pass initializealg = ShampineCollocationInit() to solve. Note that 
-        initialization can be a very difficult process for DAEs and in many cases can be 
-        numerically intractable without symbolic manipulation of the system. For an automated 
-        system that will generate numerically stable initializations, see ModelingToolkit.jl 
-        structural simplification for more details."
+        normresid = $(e.normresid) > abstol = $(e.abstol)."
     )
+
+    if isdae
+        print(io, " If you wish for the system to 
+            automatically change the algebraic variables to satisfy the algebraic constraints, 
+            please pass `initializealg = BrownBasicInit()` to solve (this option will require 
+            `using OrdinaryDiffEqNonlinearSolve`). If you wish to perform an initialization on the
+            complete u0, please pass initializealg = ShampineCollocationInit() to solve. Note that 
+            initialization can be a very difficult process for DAEs and in many cases can be 
+            numerically intractable without symbolic manipulation of the system. For an automated 
+            system that will generate numerically stable initializations, see ModelingToolkit.jl 
+            structural simplification for more details."
+        )
+    end
 end
 
 struct OverrideInitMissingAlgorithm <: Exception end
@@ -144,7 +150,7 @@ function get_initial_values(
     normresid = isdefined(integrator.opts, :internalnorm) ?
                 integrator.opts.internalnorm(tmp, t) : norm(tmp)
     if normresid > abstol
-        throw(CheckInitFailureError(normresid, abstol))
+        throw(CheckInitFailureError(normresid, abstol, true))
     end
     return u0, p, true
 end
@@ -161,7 +167,7 @@ function get_initial_values(
                 integrator.opts.internalnorm(resid, t) : norm(resid)
 
     if normresid > abstol
-        throw(CheckInitFailureError(normresid, abstol))
+        throw(CheckInitFailureError(normresid, abstol, false))
     end
     return u0, p, true
 end