remove unneeded code

Author: lkdvos

src/fusion_trees/clebsch_gordan_tensors.jl

@@ -12,6 +12,7 @@ using GradedArrays:
     SU2,
     SectorRange,
     SymmetryStyle,
+    TrivialSector,
     dual,
     istrivial,
     quantum_dimension,
@@ -21,6 +22,7 @@ using GradedArrays:
     zero_odd
 using TensorAlgebra: contract
 using TensorProducts: ⊗
+import TensorKitSectors as TKS
 
 function symbol_1j(s::SectorRange)
     cgt = clebsch_gordan_tensor(s, dual(s), trivial(s), 1)
@@ -47,92 +49,19 @@ function clebsch_gordan_tensor(
     return cgt
 end
 
-function clebsch_gordan_tensor(s1::S, s2::S, s3::S, outer_mult_index::Int) where {S}
-    return clebsch_gordan_tensor(SymmetryStyle(S), s1, s2, s3, outer_mult_index)
-end
-
-function clebsch_gordan_tensor(
-        ::AbelianStyle, s1::S, s2::S, s3::S, outer_mult_index::Int
-    ) where {S}
-    @assert outer_mult_index == 1
-    return s1 ⊗ s2 == s3 ? ones((1, 1, 1)) : zeros((1, 1, 1))
-end
-
-function clebsch_gordan_tensor(::NotAbelianStyle, s1::O2, s2::O2, s3::O2, ::Int)
-    return clebsch_gordan_tensor(s1, s2, s3)  # no outer multiplicity
-end
-
-function clebsch_gordan_tensor(s1::O2, s2::O2, s3::O2)
-    d1 = quantum_dimension(s1)
-    d2 = quantum_dimension(s2)
-    d3 = quantum_dimension(s3)
-    cgt = zeros((d1, d2, d3))
-    s3 ∉ sectors(s1 ⊗ s2) && return cgt
-
-    # adapted from TensorKit
-    l1 = sector_label(s1)
-    l2 = sector_label(s2)
-    l3 = sector_label(s3)
-    if l3 <= 0  # 0even or 0odd
-        if l1 <= 0 && l2 <= 0
-            cgt[1, 1, 1, 1] = 1.0
-        else
-            if istrivial(s3)
-                cgt[1, 2, 1, 1] = 1.0 / sqrt(2)
-                cgt[2, 1, 1, 1] = 1.0 / sqrt(2)
-            else
-                cgt[1, 2, 1, 1] = 1.0 / sqrt(2)
-                cgt[2, 1, 1, 1] = -1.0 / sqrt(2)
-            end
-        end
-    elseif l1 <= 0  # 0even or 0odd
-        cgt[1, 1, 1, 1] = 1.0
-        cgt[1, 2, 2, 1] = s1 == zero_odd(O2) ? -1.0 : 1.0
-    elseif l2 == 0
-        cgt[1, 1, 1, 1] = 1.0
-        cgt[2, 1, 2, 1] = s2 == zero_odd(O2) ? -1.0 : 1.0
-    elseif l3 == l1 + l2
-        cgt[1, 1, 1, 1] = 1.0
-        cgt[2, 2, 2, 1] = 1.0
-    elseif l3 == l1 - l2
-        cgt[1, 2, 1, 1] = 1.0
-        cgt[2, 1, 2, 1] = 1.0
-    elseif l3 == l2 - l1
-        cgt[2, 1, 1, 1] = 1.0
-        cgt[1, 2, 2, 1] = 1.0
+function clebsch_gordan_tensor(s1::S, s2::S, s3::S, outer_mult_index::Int = 1) where {S}
+    CGC = TKS.fusiontensor(GradedArrays.label.((s1, s2, s3))...)
+    outer_mult_index ∈ axes(CGC, 4) || throw(ArgumentError("invalid outer multiplicity index"))
+    if TKS.FusionStyle(S) === TKS.GenericFusion()
+        # TODO: do we want a view here?
+        return CGC[:, :, :, outer_mult_index]
+    else
+        return dropdims(CGC; dims = 4)
     end
-    return cgt
-end
-
-function clebsch_gordan_tensor(::NotAbelianStyle, s1::SU2, s2::SU2, s3::SU2, ::Int)
-    return clebsch_gordan_tensor(s1, s2, s3)  # no outer multiplicity
 end
 
-function clebsch_gordan_tensor(s1::SU2, s2::SU2, s3::SU2)
-    d1 = quantum_dimension(s1)
-    d2 = quantum_dimension(s2)
-    d3 = quantum_dimension(s3)
-    j1 = half(d1 - 1)
-    j2 = half(d2 - 1)
-    j3 = half(d3 - 1)
-    cgtensor = Array{Float64, 3}(undef, (d1, d2, d3))
-    for (i, j, k) in Iterators.product(1:d1, 1:d2, 1:d3)
-        m1 = j1 - i + 1
-        m2 = j2 - j + 1
-        m3 = j3 - k + 1
-        cgtensor[i, j, k] = clebschgordan(j1, m1, j2, m2, j3, m3)
-    end
-    return cgtensor
+# TODO: remove once TensorKitSectors fixes this
+function clebsch_gordan_tensor(s1::TrivialSector, s2::TrivialSector, s3::TrivialSector, outer_mult_index::Int = 1)
+    outer_mult_index == 1 || throw(ArgumentError("invalid outer multiplicity index"))
+    return fill(1, (1, 1, 1))
 end
-
-## TODO: Implement and move to `FusionTensorsSUNRepresentationsExt`.
-## function clebsch_gordan_tensor(
-##         ::NotAbelianStyle, s1::SU{3}, s2::SU{3}, s3::SU{3}, outer_mult_index::Int
-##     )
-##     d1 = quantum_dimension(s1)
-##     d2 = quantum_dimension(s2)
-##     d3 = quantum_dimension(s3)
-##     cgtensor = zeros(d1, d2, d3)
-##     # dummy
-##     return cgtensor
-## end