Add rrule for twist

ext/TensorKitChainRulesCoreExt/linalg.jl

@@ -77,6 +77,12 @@
     return adjoint(A), adjoint_pullback
 end
 
+function ChainRulesCore.rrule(::typeof(twist), A::AbstractTensorMap, is; inv::Bool=false)
+    tA = twist(A, is; inv)
+    twist_pullback(ΔA) = NoTangent(), twist(unthunk(ΔA), is; inv=!inv), NoTangent()
+    return tA, twist_pullback
+end
+
 function ChainRulesCore.rrule(::typeof(dot), a::AbstractTensorMap, b::AbstractTensorMap)
     dot_pullback(Δd) = NoTangent(), @thunk(b * Δd'), @thunk(a * Δd)
     return dot(a, b), dot_pullback

test/ad.jl

@@ -163,6 +163,8 @@ Vlist = ((ℂ^2, (ℂ^3)', ℂ^3, ℂ^2, (ℂ^2)'),
         test_rrule(*, A, C)
 
         test_rrule(permute, A, ((1, 3, 2), (5, 4)))
+        test_rrule(twist, A, 1)
+        test_rrule(twist, A, [1, 3])
 
         D = randn(T, V[1] ⊗ V[2] ← V[3])
         E = randn(T, V[4] ← V[5])