Implement more missing functionality (#15)

Author: mtfishman

Project.toml

@@ -1,7 +1,7 @@
 name = "ITensorBase"
 uuid = "4795dd04-0d67-49bb-8f44-b89c448a1dc7"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
-version = "0.1.3"
+version = "0.1.4"
 
 [deps]
 Accessors = "7d9f7c33-5ae7-4f3b-8dc6-eff91059b697"
@@ -12,6 +12,7 @@ MapBroadcast = "ebd9b9da-f48d-417c-9660-449667d60261"
 NamedDimsArrays = "60cbd0c0-df58-4cb7-918c-6f5607b73fde"
 UnallocatedArrays = "43c9e47c-e622-40fb-bf18-a09fc8c466b6"
 UnspecifiedTypes = "42b3faec-625b-4613-8ddc-352bf9672b8d"
+VectorInterface = "409d34a3-91d5-4945-b6ec-7529ddf182d8"
 
 [compat]
 Accessors = "0.1.39"
@@ -22,4 +23,5 @@ MapBroadcast = "0.1.5"
 NamedDimsArrays = "0.3.0"
 UnallocatedArrays = "0.1.1"
 UnspecifiedTypes = "0.1.1"
+VectorInterface = "0.5.0"
 julia = "1.10"

src/ITensorBase.jl

@@ -54,6 +54,7 @@ addtags(n::IndexName, ts) = settags(n, tags(n) ∪ tagset(ts))
 
 setprime(n::IndexName, plev) = @set n.plev = plev
 prime(n::IndexName) = setprime(n, plev(n) + 1)
+noprime(n::IndexName) = setprime(n, 0)
 
 function Base.show(io::IO, i::IndexName)
   idstr = "id=$(id(i) % 1000)"
@@ -97,6 +98,7 @@ plev(i::Index) = plev(name(i))
 addtags(i::Index, tags) = setname(i, addtags(name(i), tags))
 prime(i::Index) = setname(i, prime(name(i)))
 Base.adjoint(i::Index) = prime(i)
+noprime(i::Index) = setname(i, noprime(name(i)))
 
 # Interface
 # TODO: Overload `Base.parent` instead.
@@ -253,6 +255,10 @@ end
 # TODO: Use `replaceinds`/`mapinds`, based on
 # `replacenameddimsindices`/`mapnameddimsindices`.
 prime(a::AbstractITensor) = setinds(a, prime.(inds(a)))
+noprime(a::AbstractITensor) = setinds(a, noprime.(inds(a)))
+
+using VectorInterface: VectorInterface, scalartype
+VectorInterface.scalartype(a::AbstractITensor) = scalartype(unallocatable(a))
 
 include("quirks.jl")
 

src/quirks.jl

@@ -1,14 +1,22 @@
 # TODO: Define this properly.
 dag(i::Index) = i
+# TODO: Define this properly.
+dag(a::ITensor) = a
 # TODO: Deprecate.
 dim(i::Index) = dename(length(i))
+# TODO: Deprecate.
+dim(a::AbstractITensor) = unname(length(a))
 # TODO: Define this properly.
 hasqns(i::Index) = false
+# TODO: Define this properly.
+hasqns(i::AbstractITensor) = false
 # TODO: Deprecate.
 itensor(parent::AbstractArray, nameddimsindices) = ITensor(parent, nameddimsindices)
 function itensor(parent::AbstractArray, i1::Index, i_rest::Index...)
   return ITensor(parent, (i1, i_rest...))
 end
+# TODO: Deprecate.
+order(a::AbstractArray) = ndims(a)
 
 # This seems to be needed to get broadcasting working.
 # TODO: Investigate this and see if we can get rid of it.
@@ -23,9 +31,24 @@ function onehot(iv::Pair{<:Index,<:Int})
   return a
 end
 
-using LinearAlgebra: svd
+using LinearAlgebra: qr, svd
 # TODO: Define this in `MatrixAlgebra.jl`/`TensorAlgebra.jl`.
-function factorize(a::AbstractITensor, args...; kwargs...)
-  U, S, V = svd(a, args...; kwargs...)
-  return U, S * V
+function factorize(a::AbstractITensor, args...; maxdim=nothing, cutoff=nothing, kwargs...)
+  if isnothing(maxdim) && isnothing(cutoff)
+    Q, R = qr(a, args...)
+    return Q, R
+  else
+    error("Truncation in `factorize` not implemented yet.")
+    U, S, V = svd(a, args...; kwargs...)
+    return U, S * V
+  end
 end
+
+# TODO: Used in `ITensorMPS.jl`, decide where or if to define it.
+# Ideally this would just be a zero-dimensional `ITensor` wrapping
+# a special type, like `Zeros{UnspecifiedZero()}()`.
+struct OneITensor <: AbstractITensor end
+Base.size(::OneITensor) = ()
+Base.:*(::OneITensor, ::OneITensor) = OneITensor()
+Base.:*(::OneITensor, a::ITensor) = a
+Base.:*(a::ITensor, ::OneITensor) = a