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Merged
merged 4 commits into from
Mar 19, 2020
Merged

add issingular #42

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ea40a66
add issingular
ChrisRackauckas Mar 18, 2020
486fd71
Add `issingular` for triangular and her/sym matrix
YingboMa Mar 18, 2020
63e3ffb
Add tests and fix README
YingboMa Mar 18, 2020
023b75a
fix README and add a bunch of other dispatches for issingular
ChrisRackauckas Mar 19, 2020
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2 changes: 1 addition & 1 deletion Project.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
name = "ArrayInterface"
uuid = "4fba245c-0d91-5ea0-9b3e-6abc04ee57a9"
version = "2.5.1"
version = "2.6.0"

[deps]
LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
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5 changes: 5 additions & 0 deletions README.md
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Expand Up @@ -65,6 +65,11 @@ A `setindex!` which is always allowed.
Return an instance of the LU factorization object with the correct type
cheaply.

## issingular(A)

Return an instance of the LU factorization object with the correct type
cheaply.

## List of things to add

- https://github.com/JuliaLang/julia/issues/22216
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11 changes: 10 additions & 1 deletion src/ArrayInterface.jl
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Expand Up @@ -95,7 +95,7 @@ isstructured(::Diagonal) = true
"""
has_sparsestruct(x::AbstractArray)

determine whether `findstructralnz` accepts the parameter `x`
Determine whether `findstructralnz` accepts the parameter `x`
"""
has_sparsestruct(x) = false
has_sparsestruct(x::AbstractArray) = has_sparsestruct(typeof(x))
Expand All @@ -106,6 +106,15 @@ has_sparsestruct(x::Type{<:Bidiagonal}) = true
has_sparsestruct(x::Type{<:Tridiagonal}) = true
has_sparsestruct(x::Type{<:SymTridiagonal}) = true

"""
issingular(A::AbstractMatrix)

Determine whether a given abstract matrix is singular.
"""
issingular(A::Matrix) = !issuccess(lu(A, check=false))
issingular(A::UniformScaling) = A.λ == 0
issingular(A::Diagonal) = any(iszero,A.diag)
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One could add here

issingular(B::Bidiagonal) = any(iszero, A.dv)
issingular(S::SymTridiagonal) = diaganyzero(iszero, ldlt(S).data)
issingular(T::Tridiagonal) = !issuccess(lu(A, check=false))

And perhaps as a fallback (which fulfills the promise of the docstring)

issingular(A::AbstractMatrix) = issingular(Matrix(A))
issingular(A::AbstractSparseMatrix) = !issuccess(lu(A, check=false))


"""
findstructralnz(x::AbstractArray)

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