Strange behavior of vec() in Julia 0.7

I just got bitten by some unexpected behavior of vec() in julia 0.7. When I run the code below

N = 3
A = randn(N,N) + im .* randn(N,N)
x = randn(N)
z = x'*A
vec(z)

I get this:

julia> N = 3
3

julia> A = randn(N,N) + im .* randn(N,N)
3×3 Array{Complex{Float64},2}:
  0.382542-0.266179im   -1.69847+1.86236im    1.28885+0.694938im
 -0.177623-0.213032im  -0.607246+0.719279im  -2.87126+1.34141im 
  0.565711-0.303921im   -1.38508+0.684031im  0.416797-0.26476im 

julia> x = randn(N)
3-element Array{Float64,1}:
 -0.00922375082321524
 -0.0683463031968038 
 -0.29722269002054613

julia> z = x'*A
1×3 LinearAlgebra.Adjoint{Complex{Float64},Array{Complex{Float64},1}}:
 -0.159531+0.107347im  0.468845-0.269648im  0.0604705-0.0193976im

julia> vec(z)
3-element Array{Complex{Float64},1}:
  -0.1595307578638994 - 0.10734716516787285im 
   0.4688454575032254 + 0.2696475874174454im  
 0.060470534170491766 + 0.019397566097290375im

Notice that vec(), besides reshaping z, also computes its conjugate. Things work differently in 1.1 though:

julia> N = 3
3

julia> A = randn(N,N) + im .* randn(N,N)
3×3 Array{Complex{Float64},2}:
    2.30835+1.173im       0.777158-2.76038im   -0.434369+1.84468im 
 -0.0812661-0.674808im      1.3555+0.468595im  -0.104688+0.238554im
  -0.649005+0.0857933im  -0.556948-0.524496im   -1.19101+0.45196im 

julia> x = randn(N)
3-element Array{Float64,1}:
 -0.10756799853360234
 -1.5958910088917135 
 -0.9507274395938174 

julia> z = x'*A
1×3 LinearAlgebra.Adjoint{Complex{Float64},Array{Complex{Float64},1}}:
 0.498415+0.869177im  -1.71732+0.0477544im  1.34612-1.00883im

julia> vec(z)
3-element reshape(::LinearAlgebra.Adjoint{Complex{Float64},Array{Complex{Float64},1}}, 3) with eltype Complex{Float64}:
 0.4984145172595025 + 0.8691770844949784im  
 -1.717324546759147 + 0.047754399003301196im
 1.3461160206833889 - 1.0088254082365649im  

Since the behavior of vec() changed from 0.7 to 1.1 (I didn’t test this on 1.0), I guess this has been discussed somewhere. I did a quick search but couldn’t find anything though. Does anybody know anything about this?

This was a bug and fixed shortly after 1.0 was released. I think it was incorporated into 1.0.1.

1 Like

I see. Thanks!!!