Member access fails when SparseVector is used

[marekdedic]

Hi, I got this error while trying to use sparse matrices and vectors with Flux.

julia> a = TrackedArray(sparse([1, 2, 3]))
Tracked 3-element SparseVector{Int64,Int64}:
 1
 2
 3

julia> a[2]
ERROR: MethodError: no method matching spzeros(::Type{Int64})
Closest candidates are:
  spzeros(::Type{T}, ::Integer) where T at sparse/sparsevector.jl:47
  spzeros(::Type{Tv}, ::Integer, ::Integer) where Tv at sparse/sparsematrix.jl:1375
  spzeros(::Type{Tv}, ::Type{Ti<:Integer}, ::Integer) where {Tv, Ti<:Integer} at sparse/sparsevector.jl:48
  ...
Stacktrace:
 [1] getindex(::TrackedArray{…,SparseVector{Int64,Int64}}, ::Int64) at /home/user/.julia/v0.6/Flux/src/tracker/lib.jl:9

From what I know, the problem is a call to similar with empty tuple as last parameter (in function toarray) - In Julia, there isn't such a thing as a 0-dimensional sparse array AFAIK.

Thank you

[MikeInnes]

Yup, it fails for anything other than 1 or 2D:

x = sparse([1,2,3])
similar(x, ())

This seems like a Base bug to me -- similar should just return an Array if it can't do anything else.

You could solve it by monkey-patching similar(::SparseVector, ::Tuple{}).

[marekdedic]

Agreed, opened JuliaLang/julia#23905.

[marekdedic]

The issue JuliaLang/julia#23905 has been successfully resolved.