Define TensorAlgebra.svd, define TensorAlgebra.qr rather than ove…

…rloading `LinearAlgebra.qr` (#20)

Project.toml

@@ -1,7 +1,7 @@
 name = "TensorAlgebra"
 uuid = "68bd88dc-f39d-4e12-b2ca-f046b68fcc6a"
 authors = ["ITensor developers <[email protected]> and contributors"]
-version = "0.1.6"
+version = "0.1.7"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"

src/TensorAlgebra.jl

@@ -12,7 +12,6 @@ include("contract/output_labels.jl")
 include("contract/blockedperms.jl")
 include("contract/allocate_output.jl")
 include("contract/contract_matricize/contract.jl")
-# TODO: Rename to `TensorAlgebraLinearAlgebraExt`.
-include("LinearAlgebraExtensions/LinearAlgebraExtensions.jl")
+include("factorizations.jl")
 
 end

src/factorizations.jl

@@ -0,0 +1,45 @@
+using ArrayLayouts: LayoutMatrix
+using LinearAlgebra: LinearAlgebra, Diagonal
+
+function qr(a::AbstractArray, biperm::BlockedPermutation{2})
+  a_matricized = fusedims(a, biperm)
+  # TODO: Make this more generic, allow choosing thin or full,
+  # make sure this works on GPU.
+  q_fact, r_matricized = LinearAlgebra.qr(a_matricized)
+  q_matricized = typeof(a_matricized)(q_fact)
+  axes_codomain, axes_domain = blockpermute(axes(a), biperm)
+  axes_q = (axes_codomain..., axes(q_matricized, 2))
+  axes_r = (axes(r_matricized, 1), axes_domain...)
+  q = splitdims(q_matricized, axes_q)
+  r = splitdims(r_matricized, axes_r)
+  return q, r
+end
+
+function qr(a::AbstractArray, labels_a, labels_codomain, labels_domain)
+  # TODO: Generalize to conversion to `Tuple` isn't needed.
+  return qr(
+    a, blockedperm_indexin(Tuple(labels_a), Tuple(labels_codomain), Tuple(labels_domain))
+  )
+end
+
+function svd(a::AbstractArray, biperm::BlockedPermutation{2})
+  a_matricized = fusedims(a, biperm)
+  usv_matricized = LinearAlgebra.svd(a_matricized)
+  u_matricized = usv_matricized.U
+  s_diag = usv_matricized.S
+  v_matricized = usv_matricized.Vt
+  axes_codomain, axes_domain = blockpermute(axes(a), biperm)
+  axes_u = (axes_codomain..., axes(u_matricized, 2))
+  axes_v = (axes(v_matricized, 1), axes_domain...)
+  u = splitdims(u_matricized, axes_u)
+  # TODO: Use `DiagonalArrays.diagonal` to make it more general.
+  s = Diagonal(s_diag)
+  v = splitdims(v_matricized, axes_v)
+  return u, s, v
+end
+
+function svd(a::AbstractArray, labels_a, labels_codomain, labels_domain)
+  return svd(
+    a, blockedperm_indexin(Tuple(labels_a), Tuple(labels_codomain), Tuple(labels_domain))
+  )
+end

test/test_basics.jl

@@ -1,7 +1,7 @@
 using EllipsisNotation: var".."
-using LinearAlgebra: norm, qr
+using LinearAlgebra: norm
 using StableRNGs: StableRNG
-using TensorAlgebra: contract, contract!, fusedims, splitdims
+using TensorAlgebra: contract, contract!, fusedims, qr, splitdims, svd
 using TensorOperations: TensorOperations
 using Test: @test, @test_broken, @testset
 
@@ -222,3 +222,16 @@ end
   a′ = contract(labels_a, q, (labels_q..., label_qr), r, (label_qr, labels_r...))
   @test a ≈ a′
 end
+@testset "svd (eltype=$elt)" for elt in elts
+  a = randn(elt, 5, 4, 3, 2)
+  labels_a = (:a, :b, :c, :d)
+  labels_u = (:b, :a)
+  labels_v = (:d, :c)
+  u, s, v = svd(a, labels_a, labels_u, labels_v)
+  label_u = :u
+  label_v = :v
+  # TODO: Define multi-arg `contract`?
+  us, labels_us = contract(u, (labels_u..., label_u), s, (label_u, label_v))
+  a′ = contract(labels_a, us, labels_us, v, (label_v, labels_v...))
+  @test a ≈ a′
+end