Stop transpose(A) \ lu(B)' from overwriting A (JuliaLang#36657)

* Stop transpose(A) \ lu(B)' from overwriting `A` This fixes the following bug I just found: ```julia julia> A = randn(5,5) 5×5 Array{Float64,2}: 0.485776 1.29655 0.0790172 0.66021 -1.49472 0.971676 -1.01382 0.630476 0.479027 -0.843428 -0.264609 0.392383 0.646729 0.510696 0.34913 -0.795944 -2.47709 -1.81052 -1.0947 -0.30381 -0.938873 2.16395 -1.33484 -0.745461 1.43709 julia> transpose(A) / lu(randn(5,5))' # should not change A 5×5 Adjoint{Float64,Array{Float64,2}}: 14.36 11.9797 -7.32563 1.87016 -16.2731 -18.4415 -13.7036 10.6455 -2.47396 19.9999 8.0401 8.31723 -5.16714 2.13261 -9.637 4.19849 3.9865 -1.98478 0.714778 -4.62445 -5.36059 -2.60991 0.917052 0.290281 4.62547 julia> A # but does! 5×5 Array{Float64,2}: 14.36 -18.4415 8.0401 4.19849 -5.36059 11.9797 -13.7036 8.31723 3.9865 -2.60991 -7.32563 10.6455 -5.16714 -1.98478 0.917052 1.87016 -2.47396 2.13261 0.714778 0.290281 -16.2731 19.9999 -9.637 -4.62445 4.62547 ``` Co-authored-by: Daniel Karrasch <daniel.karrasch@posteo.de>
caleb-allen · Jul 16, 2020 · 94398d1 · 94398d1
1 parent 8a0e0c8
commit 94398d1
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diff --git a/stdlib/LinearAlgebra/src/lu.jl b/stdlib/LinearAlgebra/src/lu.jl
@@ -432,11 +432,11 @@ end
 (/)(adjA::Adjoint{<:Any,<:AbstractMatrix}, F::Adjoint{<:Any,<:LU}) = adjoint(F.parent \ adjA.parent)
 function (/)(trA::Transpose{<:Any,<:AbstractVector}, F::Adjoint{<:Any,<:LU})
     T = promote_type(eltype(trA), eltype(F))
-    return adjoint(ldiv!(F.parent, convert(AbstractVector{T}, conj(trA.parent))))
+    return adjoint(ldiv!(F.parent, conj!(copy_oftype(trA.parent, T))))
 end
 function (/)(trA::Transpose{<:Any,<:AbstractMatrix}, F::Adjoint{<:Any,<:LU})
     T = promote_type(eltype(trA), eltype(F))
-    return adjoint(ldiv!(F.parent, convert(AbstractMatrix{T}, conj(trA.parent))))
+    return adjoint(ldiv!(F.parent, conj!(copy_oftype(trA.parent, T))))
 end
 
 function det(F::LU{T}) where T

diff --git a/stdlib/LinearAlgebra/test/lu.jl b/stdlib/LinearAlgebra/test/lu.jl
@@ -360,4 +360,17 @@ end
     end
 end
 
+@testset "transpose(A) / lu(B)' should not overwrite A (#36657)" begin
+    for elty in (Float16, Float64, ComplexF64)
+        A = randn(elty, 5, 5)
+        B = randn(elty, 5, 5)
+        C = copy(A)
+        a = randn(elty, 5)
+        c = copy(a)
+        @test transpose(A) / lu(B)' ≈ transpose(A) / B'
+        @test transpose(a) / lu(B)' ≈ transpose(a) / B'
+        @test A == C
+        @test a == c
+    end
+end
 end # module TestLU