Merge branch '39-sum-over-physical-indices' into 'main'

Fix: spurious conjugate in `sum` function

See merge request tensors4fields/TensorCrossInterpolation.jl!76

Author: Marc Ritter

src/abstracttensortrain.jl

@@ -165,7 +165,7 @@ Evaluates the sum of the tensor train approximation over all lattice sites in an
 factorized manner.
 """
 function sum(tt::AbstractTensorTrain{V}) where {V}
-    v = sum(tt[1], dims=(1, 2))[1, 1, :]'
+    v = transpose(sum(tt[1], dims=(1, 2))[1, 1, :])
     for T in tt[2:end]
         v *= sum(T, dims=2)[:, 1, :]
     end

test/test_tensortrain.jl

@@ -4,16 +4,16 @@ using Zygote
 using Optim
 
 @testset "tensor train" begin
-    g(v) = 1 / (sum(v .^ 2) + 1)
+    g(v) = 1 / (sum(v .^ 2) + 1im)
     localdims = (6, 6, 6, 6)
     tolerance = 1e-8
     allindices = CartesianIndices(localdims)
 
-    tci, ranks, errors = TCI.crossinterpolate1(Float64, g, localdims; tolerance=tolerance)
+    tci, ranks, errors = TCI.crossinterpolate1(ComplexF64, g, localdims; tolerance=tolerance)
     tt = TCI.TensorTrain(tci)
     @test TCI.rank(tci) == TCI.rank(tt)
     @test TCI.linkdims(tci) == TCI.linkdims(tt)
-    gsum = 0.0
+    gsum = ComplexF64(0.0)
     for i in allindices
         @test TCI.evaluate(tci, i) ≈ TCI.evaluate(tt, i)
         @test tt(i) == TCI.evaluate(tt, i)