fix: non-scalar tangents

Project.toml

@@ -1,6 +1,6 @@
 name = "DataInterpolations"
 uuid = "82cc6244-b520-54b8-b5a6-8a565e85f1d0"
-version = "6.4.3"
+version = "6.4.4"
 
 [deps]
 FindFirstFunctions = "64ca27bc-2ba2-4a57-88aa-44e436879224"

ext/DataInterpolationsChainRulesCoreExt.jl

@@ -64,8 +64,8 @@ function u_tangent(A::LinearInterpolation, t, Δ)
     out = zero(A.u)
     idx = get_idx(A, t, A.iguesser)
     t_factor = (t - A.t[idx]) / (A.t[idx + 1] - A.t[idx])
-    out[idx] = Δ * (one(eltype(out)) - t_factor)
-    out[idx + 1] = Δ * t_factor
+    @. out[idx] = Δ * (true - t_factor)
+    @. out[idx + 1] = Δ * t_factor
     out
 end
 
@@ -78,9 +78,9 @@ function u_tangent(A::QuadraticInterpolation, t, Δ)
     Δt₀ = t₁ - t₀
     Δt₁ = t₂ - t₁
     Δt₂ = t₂ - t₀
-    out[i₀] = Δ * (t - A.t[i₁]) * (t - A.t[i₂]) / (Δt₀ * Δt₂)
-    out[i₁] = -Δ * (t - A.t[i₀]) * (t - A.t[i₂]) / (Δt₀ * Δt₁)
-    out[i₂] = Δ * (t - A.t[i₀]) * (t - A.t[i₁]) / (Δt₂ * Δt₁)
+    @. out[i₀] = Δ * (t - A.t[i₁]) * (t - A.t[i₂]) / (Δt₀ * Δt₂)
+    @. out[i₁] = -Δ * (t - A.t[i₀]) * (t - A.t[i₂]) / (Δt₀ * Δt₁)
+    @. out[i₂] = Δ * (t - A.t[i₀]) * (t - A.t[i₁]) / (Δt₂ * Δt₁)
     out
 end
 
@@ -100,7 +100,7 @@ function ChainRulesCore.rrule(::typeof(_interpolate),
         t::Number)
     deriv = derivative(A, t)
     function interpolate_pullback(Δ)
-        (NoTangent(), Tangent{typeof(A)}(; u = u_tangent(A, t, Δ)), deriv * Δ)
+        (NoTangent(), Tangent{typeof(A)}(; u = u_tangent(A, t, Δ)), sum(deriv .* Δ))
     end
     return _interpolate(A, t), interpolate_pullback
 end