Function zero() with type"Any"

General Usage
1

Hi!

Nowadays I’m learning about Julia, mainly to solve non-linear optimization problem. Because of the low efficiency of dense matrix, I transfer some of the matrix into sparse matrix. When I’m trying to multiply two matrix with type"Any", an error trough out:
ERROR: MethodError: no method matching zero(::Type{Any})

It seems that function zero() cannot have type “Any” as input, but I don’t understand why and how to solve this problem.

2

Blockquote
julia> matrix
2×2 SparseMatrixCSC{Any,Int64} with 3 stored entries:
[1, 1] = 1
[2, 1] = 1
[2, 2] = 1
julia> matrix=Any[1 1;1 2]
2×2 Array{Any,2}:
1 1
1 2
julia> matrix-matrix
ERROR: MethodError: no method matching zero(::Type{Any})
Closest candidates are:
zero(::Type{Union{Missing, T}}) where T at missing.jl:87
zero(::Type{LibGit2.GitHash}) at C:\Users\julia\AppData\Local\Julia-1.1.1\share\julia\stdlib\v1.1\LibGit2\src\oid.jl:220
zero(::Type{Pkg.Resolve.VersionWeights.VersionWeight}) at C:\Users\julia\AppData\Local\Julia-1.1.1\share\julia\stdlib\v1.1\Pkg\src\resolve\VersionWeights.jl:19

It seems that while operating sparse matrix, function zero() is used, in missing.jl, I find that:

Blockquote
for f in (:(Base.zero), :(Base.one), :(Base.oneunit))
@eval function $(f)(::Type{Union{T, Missing}}) where T
T === Any && throw(MethodError($f, (Any,))) # To prevent StackOverflowError
$f(T)
end
end

I try to delete that ,but it doesn’t work

3

Why not write matrix = [1 1;1 2]?



julia> matrix = [1 1;1 2]
2×2 Array{Int64,2}:
 1  1
 1  2

julia> matrix - matrix
2×2 Array{Int64,2}:
 0  0
 0  0
4

While using Any as an element type is probably not good style unless you have a good reason, the methods should work, so this looks like a bug. Probably non-numeric types should just use 0 here.

Please make a self-contained MWE and open an issue.

5

It appears they do work (Julia v1.1.1)

julia>  matrix=Any[1 1;1 2]
2×2 Array{Any,2}:
 1  1
 1  2

julia> matrix - matrix
2×2 Array{Int64,2}:
 0  0
 0  0
8

yeah it works in this situation… but in my problem I try to use sparse matrix to improve the operating speed, it seems like something wrong with sparse matrix in type “Any”

9

yeah… actually I’m using JuMP to do nonlinear optimization, my input is a 1*144 matrix, in the value function some entries of the matrix is constant, e.g., zero, but some others are VariableRef , so I need to use Any

10

I really need them in my question, I need to build a matrix with some entries are variable, thank you for your advice!

11

zero(Any) should definitely not be 0, and throwing an error is the right thing in the absence of a generic additive-identity object. See also #8092, #4808, and #27766, for example.

That being said, it should be possible to perform a matrix multiplication or subtraction for non-empty arrays without calling zero on the element type, by instead using the first element of the matrices to initialize the sums.

4 Likes
12

I can’t reproduce? Not sure what is the problem.
I am on Julia 1.0.3, by the way.

julia> using SparseArrays

julia> A = sparse([1,2,2],[1,1,2],[1,1,1])
2×2 SparseMatrixCSC{Int64,Int64} with 3 stored entries:
  [1, 1]  =  1
  [2, 1]  =  1
  [2, 2]  =  1

julia> B=Any[1 1;1 2]
2×2 Array{Any,2}:
 1  1
 1  2

julia> A-B
2×2 Array{Int64,2}:
 0  -1
 0  -1

julia> A-A
2×2 SparseMatrixCSC{Int64,Int64} with 0 stored entries

julia> B-B
2×2 Array{Int64,2}:
 0  0
 0  0

how did you make this?
SparseMatrixCSC{Any,Int64}, a {Any, Int64}?

Edit:
oh

julia> C = sparse([1,2,2],[1,1,2],Any[1,1,1])
2×2 SparseMatrixCSC{Any,Int64} with 3 stored entries:
  [1, 1]  =  1
  [2, 1]  =  1
  [2, 2]  =  1

julia> A-C
ERROR: MethodError: no method matching zero(::Type{Any})
13

right！But I really need sparse matrix with type Any, I don’t know how to solve this problem…

14

thank you for your reply! I’m sorry but I don’t fully understand how to use the first element of the matrices to initialize the sums, Could you show more details or give a simple example? thank you very much!

15

Why?

I think this was a suggestion as a fix for the implementation of the relevant methods, not something the user would do.

16

You could use Union{Real,VariableRef} and then define Base.zero(::Type{Union,VariableRef}) = 0.

Arguably, JuMP should define AbstractJuMPScalar <: Real (or maybe <: Number) to help with this sort of problem (AbstractJuMPScalar is the supertype of VariableRef).

2 Likes
17

I have a similar problem, but my input file is a biom file
julia> netw_results = learn_network(data_path, meta_data_path, sensitive=true, heterogeneous=false, alpha= 0.05)

ERROR: MethodError: no method matching zero(::Type{Any})

Thanks in advance