[ITensors] Remove combine-contract codepath (#1427)

Project.toml

@@ -1,7 +1,7 @@
 name = "ITensors"
 uuid = "9136182c-28ba-11e9-034c-db9fb085ebd5"
 authors = ["Matthew Fishman <[email protected]>", "Miles Stoudenmire <[email protected]>"]
-version = "0.5.8"
+version = "0.6.0"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/deprecated.jl

@@ -1,13 +1,10 @@
 
 # global_variables.jl
-@deprecate disable_combine_contract!() ITensors.disable_combine_contract()
 @deprecate disable_tblis!() ITensors.disable_tblis()
 @deprecate disable_warn_order!() ITensors.disable_warn_order()
-@deprecate enable_combine_contract!() ITensors.enable_combine_contract()
 @deprecate enable_tblis!() ITensors.enable_tblis()
 @deprecate reset_warn_order!() ITensors.reset_warn_order()
 @deprecate set_warn_order!(N) ITensors.set_warn_order(N)
-@deprecate use_combine_contract() ITensors.using_combine_contract()
 @deprecate use_debug_checks() ITensors.using_debug_checks()
 
 # index.jl

src/global_variables.jl

@@ -166,24 +166,6 @@ $(NDTensors.enable_threaded_blocksparse_docstring(@__MODULE__))
 """
 disable_threaded_blocksparse() = NDTensors._disable_threaded_blocksparse()
 
-#
-# Turn enable or disable combining QN ITensors before contracting
-#
-
-const _using_combine_contract = Ref(false)
-
-using_combine_contract() = _using_combine_contract[]
-
-function enable_combine_contract()
-  _using_combine_contract[] = true
-  return nothing
-end
-
-function disable_combine_contract()
-  _using_combine_contract[] = false
-  return nothing
-end
-
 #
 # Turn debug checks on and off
 #

src/tensor_operations/tensor_algebra.jl

@@ -23,36 +23,6 @@ function _contract(A::ITensor, B::ITensor)::ITensor
   return C
 end
 
-_contract(T::ITensor, ::Nothing) = T
-
-function can_combine_contract(A::ITensor, B::ITensor)::Bool
-  return hasqns(A) &&
-         hasqns(B) &&
-         !iscombiner(A) &&
-         !iscombiner(B) &&
-         !isdiag(A) &&
-         !isdiag(B)
-end
-
-function combine_contract(A::ITensor, B::ITensor)::ITensor
-  # Combine first before contracting
-  C::ITensor = if can_combine_contract(A, B)
-    uniqueindsA = uniqueinds(A, B)
-    uniqueindsB = uniqueinds(B, A)
-    commonindsAB = commoninds(A, B)
-    combinerA = isempty(uniqueindsA) ? nothing : combiner(uniqueindsA)
-    combinerB = isempty(uniqueindsB) ? nothing : combiner(uniqueindsB)
-    combinerAB = isempty(commonindsAB) ? nothing : combiner(commonindsAB)
-    AC = _contract(_contract(A, combinerA), combinerAB)
-    BC = _contract(_contract(B, combinerB), dag(combinerAB))
-    CC = _contract(AC, BC)
-    _contract(_contract(CC, dag(combinerA)), dag(combinerB))
-  else
-    _contract(A, B)
-  end
-  return C
-end
-
 """
     A::ITensor * B::ITensor
     contract(A::ITensor, B::ITensor)
@@ -100,10 +70,8 @@ function contract(A::ITensor, B::ITensor)::ITensor
     return iscombiner(A) ? _contract(A, B) : A[] * B
   elseif NB == 0
     return iscombiner(B) ? _contract(B, A) : B[] * A
-  else
-    C = using_combine_contract() ? combine_contract(A, B) : _contract(A, B)
-    return C
   end
+  return _contract(A, B)
 end
 
 function optimal_contraction_sequence(A::Union{Vector{<:ITensor},Tuple{Vararg{ITensor}}})

test/base/utils/TestITensorsExportedNames/TestITensorsExportedNames.jl

@@ -108,7 +108,6 @@ const ITENSORS_EXPORTED_NAMES = [
   :dims,
   :dir,
   :directsum,
-  :disable_combine_contract!,
   :disable_tblis!,
   :disable_warn_order!,
   :disk,
@@ -120,7 +119,6 @@ const ITENSORS_EXPORTED_NAMES = [
   :eigen,
   :eigs,
   :emptyITensor,
-  :enable_combine_contract!,
   :enable_tblis!,
   :energies,
   :entropy,
@@ -335,7 +333,6 @@ const ITENSORS_EXPORTED_NAMES = [
   :uniqueind,
   :uniqueindex,
   :uniqueinds,
-  :use_combine_contract,
   :use_debug_checks,
   :val,
   :vector,