From 92ad6a84de65ee99da3bdb008ea7c9b192485289 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Thu, 2 May 2024 16:13:48 +0530
Subject: [PATCH 01/25] feat: adjoints through observable functions

---
 ext/SciMLBaseZygoteExt.jl | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 1d2104cf4..c3b24d458 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -7,7 +7,7 @@ using SciMLBase
 using SciMLBase: ODESolution, remake,
                  getobserved, build_solution, EnsembleSolution,
                  NonlinearSolution, AbstractTimeseriesSolution
-using SymbolicIndexingInterface: symbolic_type, NotSymbolic, variable_index
+using SymbolicIndexingInterface: symbolic_type, NotSymbolic, variable_index, is_observed, observed, parameter_values
 using RecursiveArrayTools
 
 # This method resolves the ambiguity with the pullback defined in
@@ -109,7 +109,15 @@ end
 @adjoint function Base.getindex(VA::ODESolution, sym)
     function ODESolution_getindex_pullback(Δ)
         i = symbolic_type(sym) != NotSymbolic() ? variable_index(VA, sym) : sym
-        if i === nothing
+        if is_observed(VA, sym)
+            y, back = Zygote.pullback(VA) do sol
+                f = observed(sol, sym)
+                p = parameter_values(sol)
+                f.(sol.u,Ref(p), sol.t)
+            end
+            gs = back(Δ)
+            (gs[1], nothing)
+        elseif i === nothing
             throw(error("Zygote AD of purely-symbolic slicing for observed quantities is not yet supported. Work around this by using `A[sym,i]` to access each element sequentially in the function being differentiated."))
         else
             Δ′ = [[i == k ? Δ[j] : zero(x[1]) for k in 1:length(x)]
@@ -122,6 +130,7 @@ end
 
 @adjoint function Base.getindex(VA::ODESolution{T}, sym::Union{Tuple, AbstractVector}) where T
     function ODESolution_getindex_pullback(Δ)
+        @show typeof(Δ)
         sym = sym isa Tuple ? collect(sym) : sym
         i = map(x -> symbolic_type(x) != NotSymbolic() ? variable_index(VA, x) : x, sym)
         if i === nothing
@@ -182,15 +191,15 @@ end
     NonlinearSolution{T, N, uType, R, P, A, O, uType2}(u, args...), NonlinearSolutionAdjoint
 end
 
-@adjoint function literal_getproperty(sol::AbstractTimeseriesSolution,
-        ::Val{:u})
-    function solu_adjoint(Δ)
-        zerou = zero(sol.prob.u0)
-        _Δ = @. ifelse(Δ === nothing, (zerou,), Δ)
-        (build_solution(sol.prob, sol.alg, sol.t, _Δ),)
-    end
-    sol.u, solu_adjoint
-end
+# @adjoint function literal_getproperty(sol::AbstractTimeseriesSolution,
+#         ::Val{:u})
+#     function solu_adjoint(Δ)
+#         zerou = zero(sol.prob.u0)
+#         _Δ = @. ifelse(Δ === nothing, (zerou,), Δ)
+#         (build_solution(sol.prob, sol.alg, sol.t, _Δ),)
+#     end
+#     sol.u, solu_adjoint
+# end
 
 @adjoint function literal_getproperty(sol::SciMLBase.AbstractNoTimeSolution,
         ::Val{:u})

From 22dc7ecca9d897864f462b98f6b71edffdcda784 Mon Sep 17 00:00:00 2001
From: Dhairya Gandhi <dhairya@juliahub.com>
Date: Mon, 6 May 2024 19:33:23 +0530
Subject: [PATCH 02/25] Update ext/SciMLBaseZygoteExt.jl

Co-authored-by: Christopher Rackauckas <accounts@chrisrackauckas.com>
---
 ext/SciMLBaseZygoteExt.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index c3b24d458..df2c4df97 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -130,7 +130,6 @@ end
 
 @adjoint function Base.getindex(VA::ODESolution{T}, sym::Union{Tuple, AbstractVector}) where T
     function ODESolution_getindex_pullback(Δ)
-        @show typeof(Δ)
         sym = sym isa Tuple ? collect(sym) : sym
         i = map(x -> symbolic_type(x) != NotSymbolic() ? variable_index(VA, x) : x, sym)
         if i === nothing

From 0c2b69d92ca2baed6120bf38a6517bfe2b9ad256 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Wed, 8 May 2024 16:30:10 +0530
Subject: [PATCH 03/25] feat: allow observables in collections

---
 ext/SciMLBaseZygoteExt.jl | 50 ++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 16 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index df2c4df97..04d45baa4 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -128,25 +128,43 @@ end
     VA[sym], ODESolution_getindex_pullback
 end
 
-@adjoint function Base.getindex(VA::ODESolution{T}, sym::Union{Tuple, AbstractVector}) where T
+function obs_grads(VA, sym, obss_idx, Δ)
+    y, back = Zygote.pullback(VA) do sol
+        getindex.(Ref(sol), sym[obss_idx])
+    end
+    Dprime = reduce(hcat, Δ)
+    Dobss = eachrow(Dprime[obss_idx, :])    
+    back(Dobss)
+end
+
+function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where T
+    Δ′ = map(enumerate(VA.u)) do (t_idx, us)
+        map(enumerate(us)) do (u_idx, u)
+            if u_idx in i
+                idx = findfirst(isequal(u_idx), i)
+                Δ[t_idx][idx]
+            else
+                zero(T)
+            end
+        end
+    end
+
+    ((u = Δ′,))
+end
+
+@adjoint function getindex(VA::ODESolution{T}, sym::Union{Tuple, AbstractVector}) where T
     function ODESolution_getindex_pullback(Δ)
         sym = sym isa Tuple ? collect(sym) : sym
         i = map(x -> symbolic_type(x) != NotSymbolic() ? variable_index(VA, x) : x, sym)
-        if i === nothing
-            throw(error("Zygote AD of purely-symbolic slicing for observed quantities is not yet supported. Work around this by using `A[sym,i]` to access each element sequentially in the function being differentiated."))
-        else
-            Δ′ = map(enumerate(VA.u)) do (t_idx, us)
-                map(enumerate(us)) do (u_idx, u)
-                    if u_idx in i
-                        idx = findfirst(isequal(u_idx), i)
-                        Δ[t_idx][idx]
-                    else
-                        zero(T)
-                    end
-                end
-            end
-            (Δ′, nothing)
-        end
+
+        obss_idx = findall(s -> is_observed(VA, s), sym)
+        not_obss_idx = setdiff(1:length(sym), obss_idx)
+
+        gs_obs = obs_grads(VA, sym, obss_idx, Δ)
+        gs_not_obs = not_obs_grads(VA, sym, not_obss_idx, i, Δ)
+
+        a = Zygote.accum(gs_obs[1], gs_not_obs)
+        (a, nothing)
     end
     VA[sym], ODESolution_getindex_pullback
 end

From c61e08cc7a98b9afbd9d7d2fbdfe0360b179155d Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Wed, 8 May 2024 16:35:09 +0530
Subject: [PATCH 04/25] chore: handle no observables in collection

---
 ext/SciMLBaseZygoteExt.jl | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 04d45baa4..fcea18ea8 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -137,6 +137,10 @@ function obs_grads(VA, sym, obss_idx, Δ)
     back(Dobss)
 end
 
+function obs_grads(VA, sym, ::Nothing, Δ)
+    Zygote.nt_nothing(VA)
+end
+
 function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where T
     Δ′ = map(enumerate(VA.u)) do (t_idx, us)
         map(enumerate(us)) do (u_idx, u)
@@ -149,7 +153,8 @@ function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where T
         end
     end
 
-    ((u = Δ′,))
+    nt = Zygote.nt_nothing(VA)
+    (Zygote.accum(nt, (u = Δ′,)))
 end
 
 @adjoint function getindex(VA::ODESolution{T}, sym::Union{Tuple, AbstractVector}) where T
@@ -160,7 +165,7 @@ end
         obss_idx = findall(s -> is_observed(VA, s), sym)
         not_obss_idx = setdiff(1:length(sym), obss_idx)
 
-        gs_obs = obs_grads(VA, sym, obss_idx, Δ)
+        gs_obs = obs_grads(VA, sym, isempty(obss_idx) ? nothing : obss_idx, Δ)
         gs_not_obs = not_obs_grads(VA, sym, not_obss_idx, i, Δ)
 
         a = Zygote.accum(gs_obs[1], gs_not_obs)

From 8600a8db77ef9f73b5f3f24edc4564fcc1663401 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Wed, 8 May 2024 16:37:17 +0530
Subject: [PATCH 05/25] fix: typo

---
 ext/SciMLBaseZygoteExt.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index fcea18ea8..32ce18629 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -154,7 +154,7 @@ function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where T
     end
 
     nt = Zygote.nt_nothing(VA)
-    (Zygote.accum(nt, (u = Δ′,)))
+    Zygote.accum(nt, (u = Δ′,))
 end
 
 @adjoint function getindex(VA::ODESolution{T}, sym::Union{Tuple, AbstractVector}) where T

From 785b052f2b0c9934b08d418c33d44a32e1d3caf6 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Sun, 12 May 2024 23:58:04 +0530
Subject: [PATCH 06/25] test: add test for observable functions

---
 test/downstream/observables_autodiff.jl | 34 +++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 test/downstream/observables_autodiff.jl

diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
new file mode 100644
index 000000000..e198bd703
--- /dev/null
+++ b/test/downstream/observables_autodiff.jl
@@ -0,0 +1,34 @@
+using ModelingToolkit, OrdinaryDiffEq
+using Zygote
+
+@parameters σ ρ β
+@variables x(t) y(t) z(t) w(t)
+
+eqs = [D(D(x)) ~ σ * (y - x),
+    D(y) ~ x * (ρ - z) - y,
+    D(z) ~ x * y - β * z,
+    w ~ x + y + z + 2 * β]
+
+@mtkbuild sys = ODESystem(eqs, t)
+
+u0 = [D(x) => 2.0,
+    x => 1.0,
+    y => 0.0,
+    z => 0.0]
+
+p = [σ => 28.0,
+    ρ => 10.0,
+    β => 8 / 3]
+
+tspan = (0.0, 100.0)
+prob = ODEProblem(sys, u0, tspan, p, jac = true)
+sol = solve(prob, Tsit5())
+
+@testset "AutoDiff Observable Functions" begin
+    gs, = gradient(sol) do sol
+        sum(sol[sys.w])
+    end
+    du_ = [0., 1., 1., 1.]
+    du = [du_ for _ = sol.u]
+    @test du == gs.u
+end

From adee4f08d9acd16c0582f5be046202d058574a48 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 13 May 2024 00:00:33 +0530
Subject: [PATCH 07/25] test: add AD testset

---
 test/runtests.jl | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/runtests.jl b/test/runtests.jl
index 5e0bed4c7..f5b3c2d22 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -110,6 +110,9 @@ end
         @time @safetestset "Partial Functions" begin
             include("downstream/partial_functions.jl")
         end
+        @time @safetestset "Autodiff Observable Functions" begin
+            include("downstream/observables_autodiff.jl")
+        end
     end
 
     if !is_APPVEYOR && (GROUP == "Downstream" || GROUP == "SymbolicIndexingInterface")

From 2197a30253b3375ccac5895175f2765381593a6b Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Mon, 13 May 2024 06:55:24 -0400
Subject: [PATCH 08/25] Update test/downstream/observables_autodiff.jl

---
 test/downstream/observables_autodiff.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index e198bd703..5904cbdfc 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -1,5 +1,6 @@
 using ModelingToolkit, OrdinaryDiffEq
 using Zygote
+using ModelingToolkit: t_nounits as t, D_nounits as D
 
 @parameters σ ρ β
 @variables x(t) y(t) z(t) w(t)

From 917201484b0d4966ce56079e8d0d1bd2494c81a1 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Wed, 15 May 2024 17:55:04 +0530
Subject: [PATCH 09/25] test: add a simple DAE example; disable till
 sensitivities are turned on

---
 test/downstream/observables_autodiff.jl | 100 ++++++++++++++++++++++++
 1 file changed, 100 insertions(+)

diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index 5904cbdfc..6aa1e1afe 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -33,3 +33,103 @@ sol = solve(prob, Tsit5())
     du = [du_ for _ = sol.u]
     @test du == gs.u
 end
+
+# Lorenz
+
+@parameters σ ρ β
+@variables x(t) y(t) z(t)
+
+eqs = [D(x) ~ σ * (y - x),
+    D(y) ~ x * (ρ - z) - y,
+    D(z) ~ x * y - β * z]
+
+@named lorenz1 = ODESystem(eqs, t)
+@named lorenz2 = ODESystem(eqs, t)
+
+@parameters γ
+@variables a(t) α(t)
+connections = [0 ~ lorenz1.x + lorenz2.y + a * γ,
+    α ~ 2lorenz1.x + a * γ]
+@mtkbuild sys = ODESystem(connections, t, [a, α], [γ], systems = [lorenz1, lorenz2])
+
+u0 = [lorenz1.x => 1.0,
+    lorenz1.y => 0.0,
+    lorenz1.z => 0.0,
+    lorenz2.x => 0.0,
+    lorenz2.y => 1.0,
+    lorenz2.z => 0.0,
+    a => 2.0]
+
+p = [lorenz1.σ => 10.0,
+    lorenz1.ρ => 28.0,
+    lorenz1.β => 8 / 3,
+    lorenz2.σ => 10.0,
+    lorenz2.ρ => 28.0,
+    lorenz2.β => 8 / 3,
+    γ => 2.0]
+
+tspan = (0.0, 100.0)
+prob = ODEProblem(sys, u0, tspan, p)
+integ = init(prob, Rodas4())
+sol = solve(prob, Rodas4())
+
+gt = reduce(hcat, sol[[sys.a, sys.α]]) .+ randn.()
+
+gs, = Zygote.gradient(sol) do sol
+    mean(abs.(sol[[sys.a, sys.α]] .- gt), dims = 2)
+end
+
+# DAE
+
+using ModelingToolkit, OrdinaryDiffEq, Zygote
+using ModelingToolkitStandardLibrary
+import ModelingToolkitStandardLibrary as MSL
+using SciMLStructures
+
+function create_model(; C₁ = 3e-5, C₂ = 1e-6)
+    @variables t
+    @named resistor1 = MSL.Electrical.Resistor(R = 5.0)
+    @named resistor2 = MSL.Electrical.Resistor(R = 2.0)
+    @named capacitor1 = MSL.Electrical.Capacitor(C = C₁)
+    @named capacitor2 = MSL.Electrical.Capacitor(C = C₂)
+    @named source = MSL.Electrical.Voltage()
+    @named input_signal = MSL.Blocks.Sine(frequency = 100.0)
+    @named ground = MSL.Electrical.Ground()
+    @named ampermeter = MSL.Electrical.CurrentSensor()
+
+    eqs = [connect(input_signal.output, source.V)
+        connect(source.p, capacitor1.n, capacitor2.n)
+        connect(source.n, resistor1.p, resistor2.p, ground.g)
+        connect(resistor1.n, capacitor1.p, ampermeter.n)
+        connect(resistor2.n, capacitor2.p, ampermeter.p)]
+
+    @named circuit_model = ODESystem(eqs, t,
+        systems = [
+            resistor1, resistor2, capacitor1, capacitor2,
+            source, input_signal, ground, ampermeter,
+        ])
+end
+
+model = create_model()
+sys = structural_simplify(model)
+
+prob = ODEProblem(sys, [], (0.0, 1.0))
+sol = solve(prob, Rodas4())
+pf = getp(sol, sys.resistor1.R)
+mtkparams = SII.parameter_values(sol)
+tunables, _, _ = SS.canonicalize(SS.Tunable(), mtkparams)
+p_new = rand(length(tunables))
+
+# @testset "Adjoints with DAE" begin
+#     gs_mtkp, gs_p_new = gradient(mtkparams, p_new) do p, new_tunables
+#         new_p = SciMLStructures.replace(SciMLStructures.Tunable(), p, new_tunables)
+#         new_prob = remake(prob, p = new_p)
+#         sol = solve(new_prob, Rodas4())
+#         @show size(sol)
+#         # mean(abs.(sol[sys.ampermeter.i] .- gt))
+#         sum(sol[sys.ampermeter.i])
+#     end
+# 
+#     @test isnothing(gs_mtkp)
+#     @test length(gs_p_new) == length(p_new)
+# end

From 95cf416c0b7ff9f54ce8076d33fbe4ef0a1febb9 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Wed, 15 May 2024 18:14:39 +0530
Subject: [PATCH 10/25] test: add missing imports

---
 test/downstream/observables_autodiff.jl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index 6aa1e1afe..bfd96b85f 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -1,6 +1,8 @@
 using ModelingToolkit, OrdinaryDiffEq
 using Zygote
 using ModelingToolkit: t_nounits as t, D_nounits as D
+import SymbolicIndexingInterface as SII
+import SciMLStructures as SS
 
 @parameters σ ρ β
 @variables x(t) y(t) z(t) w(t)

From 4ce8257cdc4c8e12f0343ea73a434ad0a19e1f1d Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Thu, 16 May 2024 23:21:01 +0530
Subject: [PATCH 11/25] chore: format

---
 ext/SciMLBaseZygoteExt.jl               |  9 +++++----
 test/downstream/observables_autodiff.jl | 14 +++++++-------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index b8952f910..13eb86d13 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -7,7 +7,8 @@ using SciMLBase
 using SciMLBase: ODESolution, remake,
                  getobserved, build_solution, EnsembleSolution,
                  NonlinearSolution, AbstractTimeseriesSolution
-using SymbolicIndexingInterface: symbolic_type, NotSymbolic, variable_index, is_observed, observed, parameter_values
+using SymbolicIndexingInterface: symbolic_type, NotSymbolic, variable_index, is_observed,
+                                 observed, parameter_values
 using RecursiveArrayTools
 
 # This method resolves the ambiguity with the pullback defined in
@@ -113,7 +114,7 @@ end
             y, back = Zygote.pullback(VA) do sol
                 f = observed(sol, sym)
                 p = parameter_values(sol)
-                f.(sol.u,Ref(p), sol.t)
+                f.(sol.u, Ref(p), sol.t)
             end
             gs = back(Δ)
             (gs[1], nothing)
@@ -133,7 +134,7 @@ function obs_grads(VA, sym, obss_idx, Δ)
         getindex.(Ref(sol), sym[obss_idx])
     end
     Dprime = reduce(hcat, Δ)
-    Dobss = eachrow(Dprime[obss_idx, :])    
+    Dobss = eachrow(Dprime[obss_idx, :])
     back(Dobss)
 end
 
@@ -141,7 +142,7 @@ function obs_grads(VA, sym, ::Nothing, Δ)
     Zygote.nt_nothing(VA)
 end
 
-function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where T
+function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where {T}
     Δ′ = map(enumerate(VA.u)) do (t_idx, us)
         map(enumerate(us)) do (u_idx, u)
             if u_idx in i
diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index bfd96b85f..554b6e6f9 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -31,8 +31,8 @@ sol = solve(prob, Tsit5())
     gs, = gradient(sol) do sol
         sum(sol[sys.w])
     end
-    du_ = [0., 1., 1., 1.]
-    du = [du_ for _ = sol.u]
+    du_ = [0.0, 1.0, 1.0, 1.0]
+    du = [du_ for _ in sol.u]
     @test du == gs.u
 end
 
@@ -100,15 +100,15 @@ function create_model(; C₁ = 3e-5, C₂ = 1e-6)
     @named ampermeter = MSL.Electrical.CurrentSensor()
 
     eqs = [connect(input_signal.output, source.V)
-        connect(source.p, capacitor1.n, capacitor2.n)
-        connect(source.n, resistor1.p, resistor2.p, ground.g)
-        connect(resistor1.n, capacitor1.p, ampermeter.n)
-        connect(resistor2.n, capacitor2.p, ampermeter.p)]
+           connect(source.p, capacitor1.n, capacitor2.n)
+           connect(source.n, resistor1.p, resistor2.p, ground.g)
+           connect(resistor1.n, capacitor1.p, ampermeter.n)
+           connect(resistor2.n, capacitor2.p, ampermeter.p)]
 
     @named circuit_model = ODESystem(eqs, t,
         systems = [
             resistor1, resistor2, capacitor1, capacitor2,
-            source, input_signal, ground, ampermeter,
+            source, input_signal, ground, ampermeter
         ])
 end
 

From 839bd636afb100afd5a00f7224d88d33c47ad16f Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Thu, 16 May 2024 23:21:49 +0530
Subject: [PATCH 12/25] chore: rm unwanted adjoint

---
 ext/SciMLBaseZygoteExt.jl | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 13eb86d13..9624a227a 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -215,16 +215,6 @@ end
     NonlinearSolution{T, N, uType, R, P, A, O, uType2}(u, args...), NonlinearSolutionAdjoint
 end
 
-# @adjoint function literal_getproperty(sol::AbstractTimeseriesSolution,
-#         ::Val{:u})
-#     function solu_adjoint(Δ)
-#         zerou = zero(sol.prob.u0)
-#         _Δ = @. ifelse(Δ === nothing, (zerou,), Δ)
-#         (build_solution(sol.prob, sol.alg, sol.t, _Δ),)
-#     end
-#     sol.u, solu_adjoint
-# end
-
 @adjoint function literal_getproperty(sol::SciMLBase.AbstractNoTimeSolution,
         ::Val{:u})
     function solu_adjoint(Δ)

From 2474a8d3a1045cf5bf72dc2e6a43a06c3b0a965d Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Sat, 18 May 2024 20:51:22 +0530
Subject: [PATCH 13/25] test: check failures with SciMLSensitivity + SII

---
 test/runtests.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/runtests.jl b/test/runtests.jl
index f5b3c2d22..0a65e630e 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -3,6 +3,10 @@ using SafeTestsets
 using Test
 using SciMLBase
 
+# test with a different SciMLSensitivity branch to see full list of
+# failures
+Pkg.add(url = "https://github.com/SciML/SciMLSensitivity.jl", rev = "dg/ss")
+
 # https://github.com/JuliaArrays/FillArrays.jl/pull/163
 @test_broken isempty(detect_ambiguities(SciMLBase))
 

From f68cb05b74a1a7f68d499d74bce295fd11f5636b Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Sun, 19 May 2024 00:03:37 +0530
Subject: [PATCH 14/25] ci(SciMLSensitivity): checkout SII branch

---
 .github/workflows/Downstream.yml | 3 +++
 test/runtests.jl                 | 4 ----
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/Downstream.yml b/.github/workflows/Downstream.yml
index 4bffe0379..210fb64d0 100644
--- a/.github/workflows/Downstream.yml
+++ b/.github/workflows/Downstream.yml
@@ -61,6 +61,9 @@ jobs:
         with:
           repository: ${{ matrix.package.user }}/${{ matrix.package.repo }}
           path: downstream
+      - name: Checkout SII branch if SciMLSensitivity
+        if: "contains(${{ matrix.package.repo }}, 'SciMLSensitivity.jl')"
+        run: git checkout dg/ss
       - name: Load this and run the downstream tests
         shell: julia --color=yes --project=downstream {0}
         run: |
diff --git a/test/runtests.jl b/test/runtests.jl
index 0a65e630e..f5b3c2d22 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -3,10 +3,6 @@ using SafeTestsets
 using Test
 using SciMLBase
 
-# test with a different SciMLSensitivity branch to see full list of
-# failures
-Pkg.add(url = "https://github.com/SciML/SciMLSensitivity.jl", rev = "dg/ss")
-
 # https://github.com/JuliaArrays/FillArrays.jl/pull/163
 @test_broken isempty(detect_ambiguities(SciMLBase))
 

From 9ab29d940c80ec5f5aaf3be180d9fe66cbeaa63b Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Sun, 19 May 2024 00:12:24 +0530
Subject: [PATCH 15/25] ci(SciMLSensitivity): use correct path

---
 .github/workflows/Downstream.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/Downstream.yml b/.github/workflows/Downstream.yml
index 210fb64d0..cdea399e3 100644
--- a/.github/workflows/Downstream.yml
+++ b/.github/workflows/Downstream.yml
@@ -63,7 +63,7 @@ jobs:
           path: downstream
       - name: Checkout SII branch if SciMLSensitivity
         if: "contains(${{ matrix.package.repo }}, 'SciMLSensitivity.jl')"
-        run: git checkout dg/ss
+        run: git -C downstream checkout dg/ss
       - name: Load this and run the downstream tests
         shell: julia --color=yes --project=downstream {0}
         run: |

From a417cdd0d565093805ac037ee7e95e132951607e Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Sun, 19 May 2024 00:13:44 +0530
Subject: [PATCH 16/25] ci: revert changes

---
 .github/workflows/Downstream.yml | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/.github/workflows/Downstream.yml b/.github/workflows/Downstream.yml
index cdea399e3..4bffe0379 100644
--- a/.github/workflows/Downstream.yml
+++ b/.github/workflows/Downstream.yml
@@ -61,9 +61,6 @@ jobs:
         with:
           repository: ${{ matrix.package.user }}/${{ matrix.package.repo }}
           path: downstream
-      - name: Checkout SII branch if SciMLSensitivity
-        if: "contains(${{ matrix.package.repo }}, 'SciMLSensitivity.jl')"
-        run: git -C downstream checkout dg/ss
       - name: Load this and run the downstream tests
         shell: julia --color=yes --project=downstream {0}
         run: |

From ff9bb2c35c15eeb806c98545c4b0c08060baf8d8 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 01:45:36 +0530
Subject: [PATCH 17/25] chore: revert literal_getproperty adjoint

---
 ext/SciMLBaseZygoteExt.jl | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 9624a227a..ab25d42df 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -215,6 +215,16 @@ end
     NonlinearSolution{T, N, uType, R, P, A, O, uType2}(u, args...), NonlinearSolutionAdjoint
 end
 
+@adjoint function literal_getproperty(sol::AbstractTimeseriesSolution,
+        ::Val{:u})
+    function solu_adjoint(Δ)
+        zerou = zero(sol.prob.u0)
+        _Δ = @. ifelse(Δ === nothing, (zerou,), Δ)
+        (build_solution(sol.prob, sol.alg, sol.t, _Δ),)
+    end
+    sol.u, solu_adjoint
+end
+
 @adjoint function literal_getproperty(sol::SciMLBase.AbstractNoTimeSolution,
         ::Val{:u})
     function solu_adjoint(Δ)

From 032b927d0a050f661704fc1a4068174b321731ca Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 02:22:19 +0530
Subject: [PATCH 18/25] chore: try to avoid returning object

---
 ext/SciMLBaseZygoteExt.jl | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index ab25d42df..47d32905e 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -129,13 +129,13 @@ end
     VA[sym], ODESolution_getindex_pullback
 end
 
-function obs_grads(VA, sym, obss_idx, Δ)
+function obs_grads(VA, sym, obs_idx, Δ)
     y, back = Zygote.pullback(VA) do sol
-        getindex.(Ref(sol), sym[obss_idx])
+        getindex.(Ref(sol), sym[obs_idx])
     end
-    Dprime = reduce(hcat, Δ)
-    Dobss = eachrow(Dprime[obss_idx, :])
-    back(Dobss)
+    Δreduced = reduce(hcat, Δ)
+    Δobs = eachrow(Δreduced[obs_idx, :])
+    back(Δobs)
 end
 
 function obs_grads(VA, sym, ::Nothing, Δ)
@@ -164,11 +164,11 @@ end
         sym = sym isa Tuple ? collect(sym) : sym
         i = map(x -> symbolic_type(x) != NotSymbolic() ? variable_index(VA, x) : x, sym)
 
-        obss_idx = findall(s -> is_observed(VA, s), sym)
-        not_obss_idx = setdiff(1:length(sym), obss_idx)
+        obs_idx = findall(s -> is_observed(VA, s), sym)
+        not_obs_idx = setdiff(1:length(sym), obs_idx)
 
-        gs_obs = obs_grads(VA, sym, isempty(obss_idx) ? nothing : obss_idx, Δ)
-        gs_not_obs = not_obs_grads(VA, sym, not_obss_idx, i, Δ)
+        gs_obs = obs_grads(VA, sym, isempty(obs_idx) ? nothing : obs_idx, Δ)
+        gs_not_obs = not_obs_grads(VA, sym, not_obs_idx, i, Δ)
 
         a = Zygote.accum(gs_obs[1], gs_not_obs)
         (a, nothing)
@@ -220,7 +220,9 @@ end
     function solu_adjoint(Δ)
         zerou = zero(sol.prob.u0)
         _Δ = @. ifelse(Δ === nothing, (zerou,), Δ)
-        (build_solution(sol.prob, sol.alg, sol.t, _Δ),)
+        nt = Zygote.nt_nothing(sol)
+        gs = Zygote.accum(nt, (u = _Δ,))
+        (gs,)
     end
     sol.u, solu_adjoint
 end

From 44bfc91acb40821f7f1807952f3ade73a34ccf6b Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 03:17:38 +0530
Subject: [PATCH 19/25] build: add MSL to test deps

---
 Project.toml                            |  4 +-
 ext/SciMLBaseZygoteExt.jl               |  4 +-
 test/downstream/observables_autodiff.jl | 79 +++++++------------------
 3 files changed, 26 insertions(+), 61 deletions(-)

diff --git a/Project.toml b/Project.toml
index 061bfda7d..f74e73d3d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -68,6 +68,7 @@ Logging = "1.10"
 Makie = "0.20"
 Markdown = "1.10"
 ModelingToolkit = "8.75, 9"
+ModelingToolkitStandardLibrary = "2.7"
 PartialFunctions = "1.1"
 PrecompileTools = "1.2"
 Preferences = "1.3"
@@ -96,6 +97,7 @@ DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 DelayDiffEq = "bcd4f6db-9728-5f36-b5f7-82caef46ccdb"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
+ModelingToolkitStandardLibrary = "16a59e39-deab-5bd0-87e4-056b12336739"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 PartialFunctions = "570af359-4316-4cb7-8c74-252c00c2016b"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
@@ -111,4 +113,4 @@ UnicodePlots = "b8865327-cd53-5732-bb35-84acbb429228"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["Pkg", "Plots", "UnicodePlots", "PyCall", "PythonCall", "SafeTestsets", "Test", "StaticArrays", "StochasticDiffEq", "Aqua", "Zygote", "PartialFunctions", "DataFrames", "ModelingToolkit", "OrdinaryDiffEq", "ForwardDiff"]
+test = ["Pkg", "Plots", "UnicodePlots", "PyCall", "PythonCall", "SafeTestsets", "Test", "StaticArrays", "StochasticDiffEq", "Aqua", "Zygote", "PartialFunctions", "DataFrames", "ModelingToolkit", "ModelingToolkitStandardLibrary", "OrdinaryDiffEq", "ForwardDiff"]
diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 47d32905e..242500983 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -220,9 +220,7 @@ end
     function solu_adjoint(Δ)
         zerou = zero(sol.prob.u0)
         _Δ = @. ifelse(Δ === nothing, (zerou,), Δ)
-        nt = Zygote.nt_nothing(sol)
-        gs = Zygote.accum(nt, (u = _Δ,))
-        (gs,)
+        (build_solution(sol.prob, sol.alg, sol.t, _Δ),)
     end
     sol.u, solu_adjoint
 end
diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index 554b6e6f9..ecf38f480 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -3,6 +3,8 @@ using Zygote
 using ModelingToolkit: t_nounits as t, D_nounits as D
 import SymbolicIndexingInterface as SII
 import SciMLStructures as SS
+using ModelingToolkitStandardLibrary
+import ModelingToolkitStandardLibrary as MSL
 
 @parameters σ ρ β
 @variables x(t) y(t) z(t) w(t)
@@ -34,60 +36,18 @@ sol = solve(prob, Tsit5())
     du_ = [0.0, 1.0, 1.0, 1.0]
     du = [du_ for _ in sol.u]
     @test du == gs.u
-end
-
-# Lorenz
-
-@parameters σ ρ β
-@variables x(t) y(t) z(t)
-
-eqs = [D(x) ~ σ * (y - x),
-    D(y) ~ x * (ρ - z) - y,
-    D(z) ~ x * y - β * z]
-
-@named lorenz1 = ODESystem(eqs, t)
-@named lorenz2 = ODESystem(eqs, t)
-
-@parameters γ
-@variables a(t) α(t)
-connections = [0 ~ lorenz1.x + lorenz2.y + a * γ,
-    α ~ 2lorenz1.x + a * γ]
-@mtkbuild sys = ODESystem(connections, t, [a, α], [γ], systems = [lorenz1, lorenz2])
-
-u0 = [lorenz1.x => 1.0,
-    lorenz1.y => 0.0,
-    lorenz1.z => 0.0,
-    lorenz2.x => 0.0,
-    lorenz2.y => 1.0,
-    lorenz2.z => 0.0,
-    a => 2.0]
-
-p = [lorenz1.σ => 10.0,
-    lorenz1.ρ => 28.0,
-    lorenz1.β => 8 / 3,
-    lorenz2.σ => 10.0,
-    lorenz2.ρ => 28.0,
-    lorenz2.β => 8 / 3,
-    γ => 2.0]
-
-tspan = (0.0, 100.0)
-prob = ODEProblem(sys, u0, tspan, p)
-integ = init(prob, Rodas4())
-sol = solve(prob, Rodas4())
-
-gt = reduce(hcat, sol[[sys.a, sys.α]]) .+ randn.()
 
-gs, = Zygote.gradient(sol) do sol
-    mean(abs.(sol[[sys.a, sys.α]] .- gt), dims = 2)
+    # Observable in a vector
+    gs, = gradient(sol) do sol
+        sum(sum.(sol[[sys.w, sys.x]]))
+    end
+    du_ = [0.0, 1.0, 1.0, 2.0]
+    du = [du_ for _ in sol.u]
+    @test du == gs.u
 end
 
 # DAE
 
-using ModelingToolkit, OrdinaryDiffEq, Zygote
-using ModelingToolkitStandardLibrary
-import ModelingToolkitStandardLibrary as MSL
-using SciMLStructures
-
 function create_model(; C₁ = 3e-5, C₂ = 1e-6)
     @variables t
     @named resistor1 = MSL.Electrical.Resistor(R = 5.0)
@@ -112,15 +72,20 @@ function create_model(; C₁ = 3e-5, C₂ = 1e-6)
         ])
 end
 
-model = create_model()
-sys = structural_simplify(model)
+@testset "DAE Observable function AD" begin
+    model = create_model()
+    sys = structural_simplify(model)
+    
+    prob = ODEProblem(sys, [], (0.0, 1.0))
+    sol = solve(prob, Rodas4())
 
-prob = ODEProblem(sys, [], (0.0, 1.0))
-sol = solve(prob, Rodas4())
-pf = getp(sol, sys.resistor1.R)
-mtkparams = SII.parameter_values(sol)
-tunables, _, _ = SS.canonicalize(SS.Tunable(), mtkparams)
-p_new = rand(length(tunables))
+    gs, = gradient(sol) do sol
+        sum(sol[sys.ampermeter.i])
+    end
+    du_ = [0.2, 1.0]
+    du = [du_ for _ in sol.u]
+    @test gs.u == du
+end
 
 # @testset "Adjoints with DAE" begin
 #     gs_mtkp, gs_p_new = gradient(mtkparams, p_new) do p, new_tunables

From de2d6cd86649b6b27d2ce3bab914b7c2f5b0268f Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 05:46:31 +0530
Subject: [PATCH 20/25] chore: don't return structural tangent

---
 ext/SciMLBaseZygoteExt.jl               | 20 ++++++++++++--------
 test/downstream/observables_autodiff.jl |  6 +++---
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 242500983..cc09cc9b1 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -6,9 +6,10 @@ import Zygote: literal_getproperty
 using SciMLBase
 using SciMLBase: ODESolution, remake,
                  getobserved, build_solution, EnsembleSolution,
-                 NonlinearSolution, AbstractTimeseriesSolution
+                 NonlinearSolution, AbstractTimeseriesSolution,
+                 SciMLStructures
 using SymbolicIndexingInterface: symbolic_type, NotSymbolic, variable_index, is_observed,
-                                 observed, parameter_values
+                                 observed, parameter_values, state_values, current_time
 using RecursiveArrayTools
 
 # This method resolves the ambiguity with the pullback defined in
@@ -111,10 +112,13 @@ end
     function ODESolution_getindex_pullback(Δ)
         i = symbolic_type(sym) != NotSymbolic() ? variable_index(VA, sym) : sym
         if is_observed(VA, sym)
-            y, back = Zygote.pullback(VA) do sol
-                f = observed(sol, sym)
-                p = parameter_values(sol)
-                f.(sol.u, Ref(p), sol.t)
+            f = observed(VA, sym)
+            p = parameter_values(VA)
+            tunables, _, _ = SciMLStructures.canonicalize(SciMLStructures.Tunable(), p)
+            u = state_values(VA)
+            t = current_time(VA)
+            y, back = Zygote.pullback(u, tunables) do u, tunables
+                f.(u, Ref(tunables), t)
             end
             gs = back(Δ)
             (gs[1], nothing)
@@ -154,8 +158,7 @@ function not_obs_grads(VA::ODESolution{T}, sym, not_obss_idx, i, Δ) where {T}
         end
     end
 
-    nt = Zygote.nt_nothing(VA)
-    Zygote.accum(nt, (u = Δ′,))
+    Δ′
 end
 
 @adjoint function Base.getindex(
@@ -171,6 +174,7 @@ end
         gs_not_obs = not_obs_grads(VA, sym, not_obs_idx, i, Δ)
 
         a = Zygote.accum(gs_obs[1], gs_not_obs)
+        
         (a, nothing)
     end
     VA[sym], ODESolution_getindex_pullback
diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index ecf38f480..e03cb7fc6 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -35,7 +35,7 @@ sol = solve(prob, Tsit5())
     end
     du_ = [0.0, 1.0, 1.0, 1.0]
     du = [du_ for _ in sol.u]
-    @test du == gs.u
+    @test du == gs
 
     # Observable in a vector
     gs, = gradient(sol) do sol
@@ -43,7 +43,7 @@ sol = solve(prob, Tsit5())
     end
     du_ = [0.0, 1.0, 1.0, 2.0]
     du = [du_ for _ in sol.u]
-    @test du == gs.u
+    @test du == gs
 end
 
 # DAE
@@ -84,7 +84,7 @@ end
     end
     du_ = [0.2, 1.0]
     du = [du_ for _ in sol.u]
-    @test gs.u == du
+    @test gs == du
 end
 
 # @testset "Adjoints with DAE" begin

From c63dfbf3c61883e9a2622c2e75ed74771774644f Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 05:58:49 +0530
Subject: [PATCH 21/25] chore: fix imports

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

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index cc09cc9b1..7d9ddb084 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -6,11 +6,11 @@ import Zygote: literal_getproperty
 using SciMLBase
 using SciMLBase: ODESolution, remake,
                  getobserved, build_solution, EnsembleSolution,
-                 NonlinearSolution, AbstractTimeseriesSolution,
-                 SciMLStructures
+                 NonlinearSolution, AbstractTimeseriesSolution
 using SymbolicIndexingInterface: symbolic_type, NotSymbolic, variable_index, is_observed,
                                  observed, parameter_values, state_values, current_time
 using RecursiveArrayTools
+import SciMLStructures
 
 # This method resolves the ambiguity with the pullback defined in
 # RecursiveArrayToolsZygoteExt

From 940ea7820b6108c745bd30aee51a1cd1eb1d7461 Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 12:52:00 +0530
Subject: [PATCH 22/25] test: add MSL to downstream env

---
 test/downstream/Project.toml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/test/downstream/Project.toml b/test/downstream/Project.toml
index cf96402b8..146a277eb 100644
--- a/test/downstream/Project.toml
+++ b/test/downstream/Project.toml
@@ -3,6 +3,7 @@ BoundaryValueDiffEq = "764a87c0-6b3e-53db-9096-fe964310641d"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 JumpProcesses = "ccbc3e58-028d-4f4c-8cd5-9ae44345cda5"
 ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
+ModelingToolkitStandardLibrary = "16a59e39-deab-5bd0-87e4-056b12336739"
 NonlinearSolve = "8913a72c-1f9b-4ce2-8d82-65094dcecaec"
 Optimization = "7f7a1694-90dd-40f0-9382-eb1efda571ba"
 OptimizationMOI = "fd9f6733-72f4-499f-8506-86b2bdd0dea1"
@@ -22,6 +23,7 @@ BoundaryValueDiffEq = "5"
 ForwardDiff = "0.10"
 JumpProcesses = "9.10"
 ModelingToolkit = "8.37, 9"
+ModelingToolkitStandardLibrary = "2.7"
 NonlinearSolve = "2, 3"
 Optimization = "3"
 OptimizationMOI = "0.4"

From 8e48f1c7b178064937fe9050d5c775b91b09a11a Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 18:34:17 +0530
Subject: [PATCH 23/25] test: rm MSL from test env

---
 Project.toml | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/Project.toml b/Project.toml
index f74e73d3d..061bfda7d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -68,7 +68,6 @@ Logging = "1.10"
 Makie = "0.20"
 Markdown = "1.10"
 ModelingToolkit = "8.75, 9"
-ModelingToolkitStandardLibrary = "2.7"
 PartialFunctions = "1.1"
 PrecompileTools = "1.2"
 Preferences = "1.3"
@@ -97,7 +96,6 @@ DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 DelayDiffEq = "bcd4f6db-9728-5f36-b5f7-82caef46ccdb"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 ModelingToolkit = "961ee093-0014-501f-94e3-6117800e7a78"
-ModelingToolkitStandardLibrary = "16a59e39-deab-5bd0-87e4-056b12336739"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 PartialFunctions = "570af359-4316-4cb7-8c74-252c00c2016b"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
@@ -113,4 +111,4 @@ UnicodePlots = "b8865327-cd53-5732-bb35-84acbb429228"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["Pkg", "Plots", "UnicodePlots", "PyCall", "PythonCall", "SafeTestsets", "Test", "StaticArrays", "StochasticDiffEq", "Aqua", "Zygote", "PartialFunctions", "DataFrames", "ModelingToolkit", "ModelingToolkitStandardLibrary", "OrdinaryDiffEq", "ForwardDiff"]
+test = ["Pkg", "Plots", "UnicodePlots", "PyCall", "PythonCall", "SafeTestsets", "Test", "StaticArrays", "StochasticDiffEq", "Aqua", "Zygote", "PartialFunctions", "DataFrames", "ModelingToolkit", "OrdinaryDiffEq", "ForwardDiff"]

From d061ce47f10d99f78850e08b820727c6228b3c8b Mon Sep 17 00:00:00 2001
From: DhairyaLGandhi <dhairya@juliacomputing.com>
Date: Mon, 20 May 2024 19:08:02 +0530
Subject: [PATCH 24/25] chore: format

---
 ext/SciMLBaseZygoteExt.jl               | 2 +-
 test/downstream/observables_autodiff.jl | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/ext/SciMLBaseZygoteExt.jl b/ext/SciMLBaseZygoteExt.jl
index 7d9ddb084..4f5ff06b8 100644
--- a/ext/SciMLBaseZygoteExt.jl
+++ b/ext/SciMLBaseZygoteExt.jl
@@ -174,7 +174,7 @@ end
         gs_not_obs = not_obs_grads(VA, sym, not_obs_idx, i, Δ)
 
         a = Zygote.accum(gs_obs[1], gs_not_obs)
-        
+
         (a, nothing)
     end
     VA[sym], ODESolution_getindex_pullback
diff --git a/test/downstream/observables_autodiff.jl b/test/downstream/observables_autodiff.jl
index e03cb7fc6..974afa150 100644
--- a/test/downstream/observables_autodiff.jl
+++ b/test/downstream/observables_autodiff.jl
@@ -75,7 +75,7 @@ end
 @testset "DAE Observable function AD" begin
     model = create_model()
     sys = structural_simplify(model)
-    
+
     prob = ODEProblem(sys, [], (0.0, 1.0))
     sol = solve(prob, Rodas4())
 

From f817b52acb30b086d8d55fca55bc06e8426fdb8a Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Fri, 24 May 2024 12:50:20 -0400
Subject: [PATCH 25/25] Update CI.yml

---
 .github/workflows/CI.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 367257c3c..83c26db8f 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -14,6 +14,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         group:
           - Core
@@ -47,4 +48,4 @@ jobs:
         with:
           file: lcov.info
           token: ${{ secrets.CODECOV_TOKEN }}
-          fail_ci_if_error: true
+          fail_ci_if_error: false