From 40aaab2cf28df4a8b5292830a1c0632b3bcad83b Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Fri, 8 Nov 2024 13:25:06 -0100
Subject: [PATCH 1/2] Fix remake of ForwardDiffSensitivity

Fixes https://github.com/SciML/SciMLSensitivity.jl/issues/1137
---
 src/forward_sensitivity.jl | 10 ++++++++--
 test/forward.jl            | 12 ++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/forward_sensitivity.jl b/src/forward_sensitivity.jl
index b6527400a..f23cceed4 100644
--- a/src/forward_sensitivity.jl
+++ b/src/forward_sensitivity.jl
@@ -675,8 +675,14 @@ function SciMLBase.remake(
         {uType, tType, isinplace, P, F, K}
     _p = p === nothing ? parameter_values(prob) : p
     _f = f === nothing ? prob.f.f : f
-    _u0 = u0 === nothing ? state_values(prob, 1:(prob.f.numindvar)) :
-          u0[1:(prob.f.numindvar)]
+
+    if typeof(_f) <: ODEForwardSensitivityFunction
+        _u0 = u0 === nothing ? state_values(prob, 1:(_f.numindvar)) :
+            u0[1:(_f.numindvar)]
+    else
+        _u0 = u0 === nothing ? state_values(prob) : u0
+    end
+    
     _tspan = tspan === nothing ? prob.tspan : tspan
     ODEForwardSensitivityProblem(_f, _u0,
         _tspan, _p; sensealg = prob.problem_type.sensealg,
diff --git a/test/forward.jl b/test/forward.jl
index 08158aec3..a76f81aa4 100644
--- a/test/forward.jl
+++ b/test/forward.jl
@@ -271,3 +271,15 @@ f = prob.f
 @assert f isa ODEForwardSensitivityFunction
 @test hasproperty(f, :observed)
 @test f.observed == SciMLBase.DEFAULT_OBSERVED
+
+# `remake`: https://github.com/SciML/SciMLSensitivity.jl/issues/1137
+
+function f(du, u, p, t)
+    du[1] = dx = p[1] * u[1] - p[2] * u[1] * u[2]
+    du[2] = dy = -p[3] * u[2] + u[1] * u[2]
+end
+
+p = [1.5, 1.0, 3.0]
+ts = (0, 10)
+prob = ODEForwardSensitivityProblem(f, [1.0; 1.0], ts, p, sensealg=ForwardDiffSensitivity())
+sol = solve(prob, Tsit5())
\ No newline at end of file

From 9a8c5b24198eede160fff1bea3bd560b276fe203 Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Fri, 8 Nov 2024 15:17:31 -0100
Subject: [PATCH 2/2] Update test/forward.jl

---
 test/forward.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/forward.jl b/test/forward.jl
index a76f81aa4..71a819c8b 100644
--- a/test/forward.jl
+++ b/test/forward.jl
@@ -274,12 +274,12 @@ f = prob.f
 
 # `remake`: https://github.com/SciML/SciMLSensitivity.jl/issues/1137
 
-function f(du, u, p, t)
+function ff3(du, u, p, t)
     du[1] = dx = p[1] * u[1] - p[2] * u[1] * u[2]
     du[2] = dy = -p[3] * u[2] + u[1] * u[2]
 end
 
 p = [1.5, 1.0, 3.0]
 ts = (0, 10)
-prob = ODEForwardSensitivityProblem(f, [1.0; 1.0], ts, p, sensealg=ForwardDiffSensitivity())
+prob = ODEForwardSensitivityProblem(ff3, [1.0; 1.0], ts, p, sensealg=ForwardDiffSensitivity())
 sol = solve(prob, Tsit5())
\ No newline at end of file