Force specification of contract alg

Author: JoeyT1994

src/contractnetwork.jl

@@ -1,6 +1,13 @@
 using BackendSelection: @Algorithm_str, Algorithm
 
-default_sequence_alg = "leftassociative"
+default_contract_alg = nothing
+
+#Algorithmic defaults
+default_sequence(::Algorithm"exact") = "leftassociative"
+function set_default_kwargs(alg::Algorithm"exact")
+  sequence = get(alg, :sequence, default_sequence(alg))
+  return Algorithm("exact"; sequence)
+end
 
 function contraction_sequence(::Algorithm"leftassociative", tn::Vector{<:AbstractArray})
   return Any[i for i in 1:length(tn)]
@@ -20,11 +27,16 @@ end
 rearrange(tn::Vector{<:AbstractArray}, i::Integer) = tn[i]
 rearrange(tn::Vector{<:AbstractArray}, v::AbstractVector) = [rearrange(tn, s) for s in v]
 
-function contractnetwork(tn::Vector{<:AbstractArray}; sequence=default_sequence_alg)
-  contract_sequence = isa(sequence, String) ? contraction_sequence(tn; alg=sequence) : sequence
+function contractnetwork(alg::Algorithm"exact", tn::Vector{<:AbstractArray})
+  contract_sequence = isa(alg.sequence, String) ? contraction_sequence(tn; alg=alg.sequence) : sequence
   return recursive_contractnetwork(rearrange(tn, contract_sequence))
 end
 
-function contractnetwork(tn::AbstractTensorNetwork; sequence=default_sequence_alg)
-  return contractnetwork([tn[v] for v in vertices(tn)]; sequence)
+function contractnetwork(alg::Algorithm"exact", tn::AbstractTensorNetwork)
+  return contractnetwork(alg, [tn[v] for v in vertices(tn)])
 end
+
+function contractnetwork(tn::Union{AbstractTensorNetwork, Vector{<:AbstractArray}}; alg = default_contract_alg, kwargs...)
+  alg == nothing && error("Must specify an algorithm to contract the network with")
+  return contractnetwork(set_default_kwargs(Algorithm(alg; kwargs...)), tn)
+end

test/test_contractnetwork.jl

@@ -15,8 +15,8 @@ using Test: @test, @testset
     C = ITensor([5.0, 1.0], j)
     D = ITensor([-2.0, 3.0, 4.0, 5.0, 1.0], k)
 
-    ABCD_1 = contractnetwork([A, B, C, D]; sequence="leftassociative")
-    ABCD_2 = contractnetwork([A, B, C, D]; sequence="optimal")
+    ABCD_1 = contractnetwork([A, B, C, D]; alg = "exact", sequence="leftassociative")
+    ABCD_2 = contractnetwork([A, B, C, D]; alg = "exact", sequence="optimal")
 
     @test ABCD_1 == ABCD_2
   end
@@ -31,8 +31,8 @@ using Test: @test, @testset
       return randn(Tuple(is))
     end
 
-    z1 = contractnetwork(tn; sequence="optimal")[]
-    z2 = contractnetwork(tn; sequence="leftassociative")[]
+    z1 = contractnetwork(tn; alg = "exact", sequence="optimal")[]
+    z2 = contractnetwork(tn; alg = "exact", sequence="leftassociative")[]
 
     @test abs(z1 - z2) / abs(z1) <= 1e3*eps(Float64)
   end