SparseMatrixCSC as a general sparse container: Setindex!(…) not working for SparseMatrixCSC with vector elements (v0.7)

[HTSykora]

In my application I have a sparse matrix, but every element of this matrix is a discretised function. If I try to use SparseMatrixCSC{Array{Float64,1},Int64} as the container, setindex!(...) in 0.7 throws a stackoverflow:

julia> sa=sparse([1],[1],[Vector{Float64}(undef,3)],3,3)
3×3 SparseMatrixCSC{Array{Float64,1},Int64} with 1 stored entry:
  [1, 1]  =  [6.93279e-310, 6.93279e-310, 6.93279e-310]

julia> sa[1,1] = [1.0,2.0,3.0]
StackOverflowError:
Stacktrace:
 [1] setindex!(::SparseMatrixCSC{Array{Int64,1},Int64}, ::Array{Int64,1}, ::Int64, ::Int64) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v0.7/SparseArrays/src/sparsematrix.jl:2540 (repeats 80000 times)

This can be solved by using broadcasted setindex!(...), but it does not solve the problem adding new elements to the array:

julia> sa[1,1] .= [1.0,2.0,3.0]
3-element Array{Float64,1}:
 1.0
 2.0
 3.0

julia> sa[2,2] = [1.0,2.0,3.0]
StackOverflowError:
Stacktrace:
 [1] setindex!(::SparseMatrixCSC{Array{Float64,1},Int64}, ::Array{Float64,1}, ::Int64, ::Int64) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v0.7/SparseArrays/src/sparsematrix.jl:2540 (repeats 80000 times)

I can work around it using custom structures, but this has worked in 0.6.x.

The version producing the bug

julia> versioninfo()
Julia Version 0.7.0
Commit a4cb80f3ed (2018-08-08 06:46 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, skylake)

[HTSykora]

On discourse Sukera pointed out, that the issue originates from the following lines:

julia/stdlib/SparseArrays/src/sparsematrix.jl

Line 2538 in c8450d8

setindex!(A::SparseMatrixCSC{Tv}, B::AbstractVecOrMat, I::Integer, J::Integer) where {Tv} = setindex!(A, convert(Tv, B), I, J)

[HTSykora]

Sorry, accidently closed it...

[Seelengrab]

To mirror my thinking on discourse on here:

What I think is happening is an endless convert loop, as the B being put in is already a Tv, but is also an Array{Float64,1} and thus gets caught by the same setindex! again and again.