Showing sparse arrays in dictionaries

[ViralBShah]

This is probably more general than sparse, but at least for the sparse matrix case, I would love to show something better than .... Something like m x n sparse matrix with nnz nonzeros.

julia> a = Dict()
Dict{Any,Any} with 0 entries

julia> a["sparse"] = speye(5)
5x5 sparse matrix with 5 Float64 entries:
    [1, 1]  =  1.0
    [2, 2]  =  1.0
    [3, 3]  =  1.0
    [4, 4]  =  1.0
    [5, 5]  =  1.0

julia> a
Dict{Any,Any} with 1 entry:
  "sparse" => …

[jakebolewski]

Related performance issue with current implementation

julia> @time a = sprandn(50_000, 100_000, 0.01);
elapsed time: 3.249520351 seconds (1474 MB allocated, 7.23% gc time in 5 pauses with 3 full sweep)

julia> D = Dict("a"=>a);

julia> @time display(D)
Dict{ASCIIString,Base.SparseMatrix.SparseMatrixCSC{Float64,Int64}} with 1 entry:
  "a" => …
elapsed time: 72.493628928 seconds (29965 MB allocated, 4.88% gc time in 1291 pauses with 1 full sweep)

[mbauman]

Hah, yes, that's unfortunate. It's happening because sparse matrices print with a leading '\n'. It'd make sense for showdict to trim leading newlines, but it'd also probably be sensible to get rid of that newline in the sparse print method.

[mbauman]

This is significantly better now, but still not ideal:

julia> a
Dict{Any,Any} with 1 entry:
  "sparse" => 5x5 sparse matrix with 5 Float64 entries:…

[mbauman]

Actually, it now matches dense matrices. Is there more you want done here? If so, either the title should change or it should be closed in favor of a more general printing issue.

julia> a
Dict{Any,Any} with 2 entries:
  "dense"  => 5x5 Array{Float64,2}:…
  "sparse" => 5x5 sparse matrix with 5 Float64 entries:…

[ViralBShah]

This is completely fine. I think we can close this specific issue.