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lkdvos merged 2 commits into from
Aug 19, 2026
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BraidingTensor constructors with SumSpace instances #69

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fe509f7
overload BraidingTensor constructors properly
lkdvos Aug 18, 2026
7087c48
add regression test
lkdvos Aug 18, 2026
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15 changes: 15 additions & 0 deletions src/tensors/tensoroperations.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,12 @@ function TK.BraidingTensor{T, S}(
V1::SumSpace{S}, V2::SumSpace{S}, adjoint::Bool = false
) where {T, S}
τtype = TK.braidingtensortype(S, T)
return τtype(V1, V2, adjoint)
end
function TK.BraidingTensor{T, S, A}(
V1::SumSpace{S}, V2::SumSpace{S}, adjoint::Bool = false
) where {T, S, A}
τtype = BraidingTensor{T, S, A}
cod, dom = adjoint ? (V1 ⊗ V2, V2 ⊗ V1) : (V2 ⊗ V1, V1 ⊗ V2)
tdst = SparseBlockTensorMap{τtype}(undef, cod, dom)
Vs = eachspace(tdst)
Expand All @@ -130,3 +136,12 @@ function TK.BraidingTensor{T, S}(
end
return tdst
end

TK.braidingtensortype(::Type{SumSpace{S}}, ::Type{TorA}) where {S <: IndexSpace, TorA} =
TK.braidingtensortype(S, TorA)

# TODO: remove once proper promotion rules in TensorKit are in place
TK.BraidingTensor{T, S, A}(V1::S, V2::SumSpace{S}, adjoint::Bool = false) where {T, S, A} =
BraidingTensor{T, S, A}(promote(V1, V2)..., adjoint)
TK.BraidingTensor{T, S, A}(V1::SumSpace{S}, V2::S, adjoint::Bool = false) where {T, S, A} =
BraidingTensor{T, S, A}(promote(V1, V2)..., adjoint)
12 changes: 12 additions & 0 deletions test/abstracttensor/braidingtensor.jl
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@@ -1,6 +1,7 @@
using Test
using TestExtras
using TensorKit
using TensorKit: ℙ
using BlockTensorKit
using Random

Expand Down Expand Up @@ -34,3 +35,14 @@ Random.seed!(1234)
@test !(y ≈ braid(x, ((2, 1), (3,)), (2, 1, 3)))
end
end

@testset "Issue #68" begin
x = randn(ComplexF64, (⊞(ℙ^1) ⊗ ⊞(ℙ^1)) ← ⊞(ℙ^1))
O = randn(ComplexF64, ((ℙ^1 ⊞ ℙ^4 ⊞ ℙ^16 ⊞ ℙ^4) ⊗ ⊞(ℙ^2)) ← (⊞(ℙ^2) ⊗ ⊞(ℙ^1)))
A = randn(ComplexF64, (ℙ^4 ⊗ F^2 ⊗ (ℙ^2)') ← ℙ^1)
Ab = randn(ComplexF64, (ℙ^4 ⊗ ℙ^2 ⊗ (ℙ^2)') ← ℙ^1)

@plansor y[-1 -2; -3] ≔ A[-1 4 2; 1] * O[-2 6; 4 5] * τ[5 7; 2 3] *
conj(Ab[-3 6 7; 8]) * x[1 3; 8]
@test space(y) == (⊞(ℙ^4) ⊗ ⊞(ℙ^1)) ← ⊞(ℙ^4)
end
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