[ITensors] Call out to TensorOperations.jl for optimal sequence finding

Project.toml

@@ -29,11 +29,13 @@ Zeros = "bd1ec220-6eb4-527a-9b49-e79c3db6233b"
 
 [weakdeps]
 HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f"
+TensorOperations = "6aa20fa7-93e2-5fca-9bc0-fbd0db3c71a2"
 VectorInterface = "409d34a3-91d5-4945-b6ec-7529ddf182d8"
 ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"
 
 [extensions]
 ITensorsHDF5Ext = "HDF5"
+ITensorsTensorOperationsExt = "TensorOperations"
 ITensorsVectorInterfaceExt = "VectorInterface"
 ITensorsZygoteRulesExt = "ZygoteRules"
 
@@ -58,6 +60,7 @@ SimpleTraits = "0.9.4"
 SparseArrays = "<0.0.1, 1.10"
 StaticArrays = "0.12, 1.0"
 Strided = "1.1, 2"
+TensorOperations = "5.1.4"
 TimerOutputs = "0.5.5"
 TupleTools = "1.2"
 VectorInterface = "0.4, 0.5"
@@ -68,5 +71,6 @@ julia = "1.10"
 [extras]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f"
+TensorOperations = "6aa20fa7-93e2-5fca-9bc0-fbd0db3c71a2"
 VectorInterface = "409d34a3-91d5-4945-b6ec-7529ddf182d8"
 ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"

ext/ITensorsTensorOperationsExt/ITensorsTensorOperationsExt.jl

@@ -0,0 +1,14 @@
+module ITensorsTensorOperationsExt
+
+using ITensors: ITensors, ITensor, dim, inds
+using NDTensors.AlgorithmSelection: @Algorithm_str
+using TensorOperations: TensorOperations, optimaltree
+
+function ITensors.optimal_contraction_sequence(As::Union{Vector{<:ITensor},Tuple{Vararg{ITensor}}})
+  network = collect.(inds.(As))
+  inds_to_dims = Dict(i => Float64(dim(i)) for i in unique(reduce(vcat, network)))
+  seq, _ = optimaltree(network, inds_to_dims)
+  return seq
+end
+
+end

src/ITensors.jl

@@ -51,9 +51,6 @@ Documentation: https://itensor.github.io/ITensors.jl/stable/
 module ITensors
 include("usings.jl")
 include("utils.jl")
-include("lib/ContractionSequenceOptimization/src/ContractionSequenceOptimization.jl")
-# TODO: `using .ContractionSequenceOptimization: ContractionSequenceOptimization, ...`.
-using .ContractionSequenceOptimization
 include("lib/LazyApply/src/LazyApply.jl")
 # TODO: `using .LazyApply: LazyApply, ...`.
 using .LazyApply
@@ -105,6 +102,7 @@ include("indexset.jl")
 include("itensor.jl")
 include("qn/flux.jl")
 include("oneitensor.jl")
+include("tensor_operations/contraction_cost.jl")
 include("tensor_operations/tensor_algebra.jl")
 include("tensor_operations/matrix_algebra.jl")
 include("tensor_operations/permutations.jl")

src/imports.jl

@@ -81,9 +81,6 @@ import Base.Broadcast:
   broadcastable,
   instantiate
 
-import ITensors.ContractionSequenceOptimization:
-  contraction_cost, optimal_contraction_sequence
-
 import Adapt: adapt_structure, adapt_storage
 
 import LinearAlgebra: