define fusiontree_eltype

Author: ogauthe

src/fusion_trees/fusiontree.jl

@@ -151,6 +151,9 @@ function SymmetrySectors.arguments(f::SectorFusionTree{<:SectorProduct,1})
   end
 end
 
+# TBD change type depending on AbelianStyle?
+fusiontree_eltype(::Type{<:AbstractSector}) = Float64
+
 #
 # =====================================  Internals  ========================================
 #

src/fusiontensor/base_interface.jl

@@ -92,8 +92,8 @@ end
 Base.permutedims(ft::FusionTensor, args...) = fusiontensor_permutedims(ft, args...)
 
 function Base.similar(ft::FusionTensor, ::Type{T}) where {T}
-  # fusion trees have Float64 eltype: need compatible type
-  @assert promote_type(T, Float64) === T
+  # some fusion trees have Float64 eltype: need compatible type
+  @assert promote_type(T, fusiontree_eltype(sector_type(ft))) === T
   mat = similar(data_matrix(ft), T)
   initialize_allowed_sectors!(mat)
   return FusionTensor(mat, codomain_axes(ft), domain_axes(ft), trees_block_mapping(ft))

src/fusiontensor/fusiontensor.jl

@@ -167,10 +167,10 @@ end
 function initialize_data_matrix(
   elt::Type{<:Number}, codomain_fused_axes::FusedAxes, domain_fused_axes::FusedAxes
 )
-  # fusion trees have Float64 eltype: need compatible type
-  promoted = promote_type(elt, Float64)
   mat_row_axis = fused_axis(codomain_fused_axes)
   mat_col_axis = dual(fused_axis(domain_fused_axes))
+  # non-abelian fusion trees have float eltype: need compatible type
+  promoted = promote_type(elt, fusiontree_eltype(sector_type(mat_row_axis)))
   mat = BlockSparseArray{promoted}(mat_row_axis, mat_col_axis)
   initialize_allowed_sectors!(mat)
   return mat

test/basics/test_fusion_trees.jl

@@ -9,6 +9,7 @@ using FusionTensors:
   arrows,
   branch_sectors,
   build_trees,
+  fusiontree_eltype,
   leaves,
   outer_multiplicity_indices,
   root_sector
@@ -41,6 +42,8 @@ using SymmetrySectors: ×, SectorProduct, SU, SU2, TrivialSector, arguments
   @test branch_sectors(f) == (q,)
   @test outer_multiplicity_indices(f) == (1,)
   @test convert(Array, f) ≈ ones((1, 1, 1))
+
+  @test fusiontree_eltype(sector_type(f)) === eltype(convert(Array, f))
 end
 
 @testset "SU(2) SectorFusionTree" begin
@@ -54,6 +57,7 @@ end
   @test outer_multiplicity_indices(f) == ()
   @test sector_type(f) == typeof(j2)
   @test convert(Array, f) ≈ I(2)
+  @test fusiontree_eltype(sector_type(f)) === eltype(convert(Array, f))
 
   f = only(build_trees((j2,), (true,)))
   @test arrows(f) == (true,)