From cad74f6165ecc503fb88adbb2f27391487baaebe Mon Sep 17 00:00:00 2001
From: Fredrik Ekre <fredrik.ekre@chalmers.se>
Date: Wed, 12 Jul 2017 01:48:52 +0200
Subject: [PATCH] use in-place inv, since lufact already made a copy

---
 base/linalg/dense.jl | 2 +-
 base/linalg/lu.jl    | 6 ++++--
 test/linalg/lu.jl    | 1 +
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/base/linalg/dense.jl b/base/linalg/dense.jl
index 46d78399e2061c..da370e26484985 100644
--- a/base/linalg/dense.jl
+++ b/base/linalg/dense.jl
@@ -653,7 +653,7 @@ function inv(A::StridedMatrix{T}) where T
         Ai = inv(LowerTriangular(AA))
         Ai = convert(typeof(parent(Ai)), Ai)
     else
-        Ai = inv(lufact(AA))
+        Ai = inv!(lufact(AA))
         Ai = convert(typeof(parent(Ai)), Ai)
     end
     return Ai
diff --git a/base/linalg/lu.jl b/base/linalg/lu.jl
index 192900f92c69a8..be825281f0660a 100644
--- a/base/linalg/lu.jl
+++ b/base/linalg/lu.jl
@@ -202,6 +202,7 @@ convert(::Type{LU{T,S}}, F::LU) where {T,S} = LU{T,S}(convert(S, F.factors), F.i
 convert(::Type{Factorization{T}}, F::LU{T}) where {T} = F
 convert(::Type{Factorization{T}}, F::LU) where {T} = convert(LU{T}, F)
 
+copy(A::LU{T,S}) where {T,S} = LU{T,S}(copy(A.factors), copy(A.ipiv), A.info)
 
 size(A::LU) = size(A.factors)
 size(A::LU,n) = size(A.factors,n)
@@ -313,8 +314,9 @@ end
 
 inv!(A::LU{<:BlasFloat,<:StridedMatrix}) =
     @assertnonsingular LAPACK.getri!(A.factors, A.ipiv) A.info
-inv(A::LU{<:BlasFloat,<:StridedMatrix}) =
-    inv!(LU(copy(A.factors), copy(A.ipiv), copy(A.info)))
+inv!(A::LU{T,<:StridedMatrix}) where {T} =
+    @assertnonsingular A_ldiv_B!(A.factors, copy(A), eye(T, size(A, 1))) A.info
+inv(A::LU{<:BlasFloat,<:StridedMatrix}) = inv!(copy(A))
 
 function _cond1Inf(A::LU{<:BlasFloat,<:StridedMatrix}, p::Number, normA::Real)
     if p != 1 && p != Inf
diff --git a/test/linalg/lu.jl b/test/linalg/lu.jl
index 10c50463fa101a..541fb19ae24acd 100644
--- a/test/linalg/lu.jl
+++ b/test/linalg/lu.jl
@@ -64,6 +64,7 @@ debug && println("(Automatic) Square LU decomposition. eltya: $eltya, eltyb: $el
         @test l*u ≈ a[p,:]
         @test (l*u)[invperm(p),:] ≈ a
         @test a * inv(lua) ≈ eye(n)
+        @test copy(lua) == lua
 
         lstring = sprint(show,l)
         ustring = sprint(show,u)