Allow vectors in reflectorApply! (JuliaLang#42874)

Co-authored-by: Sheehan Olver <solver@mac.com>

Author: 2 people

stdlib/LinearAlgebra/src/generic.jl

@@ -1516,9 +1516,9 @@ end
 end
 
 # apply reflector from left
-@inline function reflectorApply!(x::AbstractVector, τ::Number, A::AbstractMatrix)
+@inline function reflectorApply!(x::AbstractVector, τ::Number, A::AbstractVecOrMat)
     require_one_based_indexing(x)
-    m, n = size(A)
+    m, n = size(A, 1), size(A, 2)
     if length(x) != m
         throw(DimensionMismatch("reflector has length $(length(x)), which must match the first dimension of matrix A, $m"))
     end

stdlib/LinearAlgebra/src/qr.jl

@@ -270,13 +270,13 @@ function qrfactPivotedUnblocked!(A::AbstractMatrix)
 
         # Compute reflector of columns j
         x = view(A, j:m, j)
-        τj = LinearAlgebra.reflector!(x)
+        τj = reflector!(x)
         τ[j] = τj
 
         # Update trailing submatrix with reflector
-        LinearAlgebra.reflectorApply!(x, τj, view(A, j:m, j+1:n))
+        reflectorApply!(x, τj, view(A, j:m, j+1:n))
     end
-    return LinearAlgebra.QRPivoted{eltype(A), typeof(A)}(A, τ, piv)
+    return QRPivoted{eltype(A), typeof(A)}(A, τ, piv)
 end
 
 # LAPACK version

stdlib/LinearAlgebra/test/generic.jl

@@ -256,6 +256,18 @@ end
     @test_throws DimensionMismatch reflect!([x; x], y, c, s)
 end
 
+@testset "LinearAlgebra.reflectorApply!" begin
+    for T in (Float64, ComplexF64)
+        x = rand(T, 6)
+        τ = rand(T)
+        A = rand(T, 6)
+        B = LinearAlgebra.reflectorApply!(x, τ, copy(A))
+        C = LinearAlgebra.reflectorApply!(x, τ, reshape(copy(A), (length(A), 1)))
+        @test B[1] ≈ C[1] ≈ A[1] - conj(τ)*(A[1] + dot(x[2:end], A[2:end]))
+        @test B[2:end] ≈ C[2:end] ≈ A[2:end] - conj(τ)*(A[1] + dot(x[2:end], A[2:end]))*x[2:end]
+    end
+end
+
 @testset "LinearAlgebra.axp(b)y! for element type without commutative multiplication" begin
     α = [1 2; 3 4]
     β = [5 6; 7 8]