Improve dual detection and error message

.github/workflows/CI.yml

@@ -15,6 +15,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         group:
           - Core

ext/DiffEqBaseCUDAExt.jl

@@ -2,7 +2,8 @@ module DiffEqBaseCUDAExt
 
 using DiffEqBase, CUDA
 
-function DiffEqBase.ODE_DEFAULT_NORM(u::CuArray{T},t) where {T <: Union{AbstractFloat, Complex}}
+function DiffEqBase.ODE_DEFAULT_NORM(
+        u::CuArray{T}, t) where {T <: Union{AbstractFloat, Complex}}
     sqrt(sum(DiffEqBase.sse, u; init = DiffEqBase.sse(zero(T))) / DiffEqBase.totallength(u))
 end
 

src/forwarddiff.jl

@@ -112,6 +112,65 @@ https://discourse.julialang.org/t/typeerror-in-julia-turing-when-sampling-for-a-
     end
 end
 
+const FORWARDDIFF_AUTODETECTION_FAILURE_MESSAGE = """
+                                Failed to automatically detect ForwardDiff compatability of
+                                the parameter object. In order for ForwardDiff.jl automatic
+                                differentiation to work on a solution object, the state of
+                                the differential equation or nonlinear solve (`u0`) needs to
+                                be converted to a Dual type which matches the values being
+                                differentiated. For example, for a loss function loss(p)
+                                where `p`` is a `Vector{Float64}`, this conversion is
+                                equivalent to:
+
+                                ```julia
+                                # Convert u0 to match the new Dual element type of `p`
+                                _prob = remake(prob, u0 = eltype(p).(prob.u0))
+                                ```
+
+                                In most cases, SciML tools are able to do this conversion
+                                automatically. However, it seems you have provided a
+                                parameter type for which this automatic conversion has failed.
+
+                                To fix this, you can do the conversion yourself. For example,
+                                if you have a parameter vector being optimized `p` which is
+                                then put into an odd struct, you can manually convert `u0`
+                                to match `p`:
+
+                                ```julia
+                                function loss(p)
+                                    _prob = remake(prob, u0 = eltype(p).(prob.u0), p = MyStruct(p))
+                                    sol = solve(_prob, ...)
+                                    # do stuff on sol
+                                end
+                                ```
+
+                                Or you can define a dispatch on `DiffEqBase.anyeltypedual`
+                                which tells the system what fields to interpret as the
+                                differentiable parts. For example, to support ODESolutions
+                                as parameters we tell it the data is `sol.u` and `sol.t` via:
+
+                                ```julia
+                                function DiffEqBase.anyeltypedual(sol::ODESolution, counter = 0)
+                                    DiffEqBase.anyeltypedual((sol.u, sol.t))
+                                end
+                                ```
+
+                                If you have defined this on a common type which should
+                                be more generally supported, please open a pull request
+                                adding this dispatch. If you need help defining this dispatch,
+                                feel free to open an issue.
+                                """
+
+struct ForwardDiffAutomaticDetectionFailure <: Exception end
+
+function Base.showerror(io::IO, e::ForwardDiffAutomaticDetectionFailure)
+    print(io, FORWARDDIFF_AUTODETECTION_FAILURE_MESSAGE)
+end
+
+function anyeltypedual(::Type{Union{}})
+    throw(ForwardDiffAutomaticDetectionFailure())
+end
+
 # Opt out since these are using for preallocation, not differentiation
 function anyeltypedual(x::Union{ForwardDiff.AbstractConfig, Module},
         ::Type{Val{counter}} = Val{0}) where {counter}
@@ -192,6 +251,17 @@ function anyeltypedual(sol::RecursiveArrayTools.AbstractDiffEqArray, counter = 0
     diffeqmapreduce(anyeltypedual, promote_dual, (sol.u, sol.t))
 end
 
+function anyeltypedual(prob::Union{ODEProblem, SDEProblem, RODEProblem, DDEProblem},
+        ::Type{Val{counter}} = Val{0}) where {counter} where {N, T <: NTuple{N, <:Number}}
+    anyeltypedual((prob.u0, prob.p, prob.tspan))
+end
+
+function anyeltypedual(
+        prob::Union{NonlinearProblem, NonlinearLeastSquaresProblem, OptimizationProblem},
+        ::Type{Val{counter}} = Val{0}) where {counter} where {N, T <: NTuple{N, <:Number}}
+    anyeltypedual((prob.u0, prob.p))
+end
+
 function anyeltypedual(x::Number, ::Type{Val{counter}} = Val{0}) where {counter}
     anyeltypedual(typeof(x))
 end

src/solve.jl

@@ -1065,7 +1065,7 @@ end
 
 function solve_up(prob::Union{AbstractDEProblem, NonlinearProblem}, sensealg, u0, p,
         args...; kwargs...)
-    alg = extract_alg(args, kwargs,  has_kwargs(prob) ? prob.kwargs : kwargs)
+    alg = extract_alg(args, kwargs, has_kwargs(prob) ? prob.kwargs : kwargs)
     if isnothing(alg) || !(alg isa AbstractDEAlgorithm) # Default algorithm handling
         _prob = get_concrete_problem(prob, !(prob isa DiscreteProblem); u0 = u0,
             p = p, kwargs...)

test/forwarddiff_dual_detection.jl

@@ -328,3 +328,10 @@ t = ForwardDiff.Dual{ForwardDiff.Tag{DiffEqBase.OrdinaryDiffEqTag, Float64}, Flo
 @test DiffEqBase.promote_u0(u0, p, t) isa AbstractArray{<:ForwardDiff.Dual}
 u0 = [1.0 + 1im, 2.0, 3.0]
 @test DiffEqBase.promote_u0(u0, p, t) isa AbstractArray{<:Complex{<:ForwardDiff.Dual}}
+
+# Issue https://github.com/SciML/NonlinearSolve.jl/issues/440
+f(u, p, t) = [u[2], 1.5u[1]^2]
+ode = ODEProblem(f, [0.0, 0.0], (0, 1))
+@inferred DiffEqBase.anyeltypedual(ode)
+ode = NonlinearProblem(f, [0.0, 0.0], (0, 1))
+@inferred DiffEqBase.anyeltypedual(ode)