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Permit Bidiagonal represents empty matrix #38392

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Dec 9, 2020
Merged

Permit Bidiagonal represents empty matrix #38392

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6 changes: 3 additions & 3 deletions stdlib/LinearAlgebra/src/bidiag.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ struct Bidiagonal{T,V<:AbstractVector{T}} <: AbstractMatrix{T}
uplo::Char # upper bidiagonal ('U') or lower ('L')
function Bidiagonal{T,V}(dv, ev, uplo::AbstractChar) where {T,V<:AbstractVector{T}}
require_one_based_indexing(dv, ev)
if length(ev) != length(dv)-1
if length(ev) != max(length(dv)-1, 0)
throw(DimensionMismatch("length of diagonal vector is $(length(dv)), length of off-diagonal vector is $(length(ev))"))
end
new{T,V}(dv, ev, uplo)
Expand Down Expand Up @@ -352,7 +352,7 @@ function diag(M::Bidiagonal, n::Integer=0)
end

function +(A::Bidiagonal, B::Bidiagonal)
if A.uplo == B.uplo
if A.uplo == B.uplo || length(A.dv) == 0
Bidiagonal(A.dv+B.dv, A.ev+B.ev, A.uplo)
else
newdv = A.dv+B.dv
Expand All @@ -361,7 +361,7 @@ function +(A::Bidiagonal, B::Bidiagonal)
end

function -(A::Bidiagonal, B::Bidiagonal)
if A.uplo == B.uplo
if A.uplo == B.uplo || length(A.dv) == 0
Bidiagonal(A.dv-B.dv, A.ev-B.ev, A.uplo)
else
newdv = A.dv-B.dv
Expand Down
7 changes: 4 additions & 3 deletions stdlib/LinearAlgebra/src/structuredbroadcast.jl
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Expand Up @@ -70,11 +70,12 @@ find_uplo(a) = nothing
find_uplo(bc::Broadcasted) = mapreduce(find_uplo, merge_uplos, bc.args, init=nothing)

function structured_broadcast_alloc(bc, ::Type{<:Bidiagonal}, ::Type{ElType}, n) where {ElType}
uplo = find_uplo(bc)
uplo = n > 0 ? find_uplo(bc) : 'U'
n1 = max(n - 1, 0)
if uplo == 'T'
return Tridiagonal(Array{ElType}(undef, n-1), Array{ElType}(undef, n), Array{ElType}(undef, n-1))
return Tridiagonal(Array{ElType}(undef, n1), Array{ElType}(undef, n), Array{ElType}(undef, n1))
end
return Bidiagonal(Array{ElType}(undef, n),Array{ElType}(undef, n-1), uplo)
return Bidiagonal(Array{ElType}(undef, n),Array{ElType}(undef, n1), uplo)
end
structured_broadcast_alloc(bc, ::Type{<:SymTridiagonal}, ::Type{ElType}, n) where {ElType} =
SymTridiagonal(Array{ElType}(undef, n),Array{ElType}(undef, n-1))
Expand Down
48 changes: 45 additions & 3 deletions stdlib/LinearAlgebra/test/bidiag.jl
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Expand Up @@ -26,17 +26,19 @@ Random.seed!(1)
ev += im*convert(Vector{elty}, rand(1:10, n-1))
end
end
dv0 = zeros(elty, 0)
ev0 = zeros(elty, 0)

@testset "Constructors" begin
for (x, y) in ((dv, ev), (GenericArray(dv), GenericArray(ev)))
for (x, y) in ((dv0, ev0), (dv, ev), (GenericArray(dv), GenericArray(ev)))
# from vectors
ubd = Bidiagonal(x, y, :U)
lbd = Bidiagonal(x, y, :L)
@test ubd != lbd
@test ubd != lbd || x === dv0
@test ubd.dv === x
@test lbd.ev === y
@test_throws ArgumentError Bidiagonal(x, y, :R)
@test_throws DimensionMismatch Bidiagonal(x, x, :U)
x == dv0 || @test_throws DimensionMismatch Bidiagonal(x, x, :U)
@test_throws MethodError Bidiagonal(x, y)
# from matrix
@test Bidiagonal(ubd, :U) == Bidiagonal(Matrix(ubd), :U) == ubd
Expand Down Expand Up @@ -593,4 +595,44 @@ Base.transpose(n::MyNotANumberType) = n
@test transpose(copy(tB)) == B
end

@testset "empty bidiagonal matrices" begin
dv0 = zeros(0)
ev0 = zeros(0)
zm = zeros(0, 0)
ubd = Bidiagonal(dv0, ev0, :U)
lbd = Bidiagonal(dv0, ev0, :L)
@test size(ubd) == (0, 0)
@test_throws BoundsError getindex(ubd, 1, 1)
@test_throws BoundsError setindex!(ubd, 0.0, 1, 1)
@test similar(ubd) == ubd
@test similar(lbd, Int) == zeros(Int, 0, 0)
@test ubd == zm
@test lbd == zm
@test ubd == lbd
@test ubd * ubd == ubd
@test lbd + lbd == lbd
@test lbd' == ubd
@test ubd' == lbd
@test triu(ubd, 1) == ubd
@test triu(lbd, 1) == ubd
@test tril(ubd, -1) == ubd
@test tril(lbd, -1) == ubd
@test_throws ArgumentError triu(ubd)
@test_throws ArgumentError tril(ubd)
@test sum(ubd) == 0.0
@test reduce(+, ubd) == 0.0
@test reduce(+, ubd, dims=1) == zeros(1, 0)
@test reduce(+, ubd, dims=2) == zeros(0, 1)
@test hcat(ubd, ubd) == zm
@test vcat(ubd, lbd) == zm
@test hcat(lbd, ones(0, 3)) == ones(0, 3)
@test fill!(copy(ubd), 1.0) == ubd
@test map(abs, ubd) == zm
@test lbd .+ 1 == zm
@test lbd + ubd isa Bidiagonal
@test lbd .+ ubd isa Bidiagonal
@test ubd * 5 == ubd
@test ubd .* 3 == ubd
end

end # module TestBidiagonal
1 change: 1 addition & 0 deletions stdlib/SparseArrays/src/sparsematrix.jl
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Expand Up @@ -568,6 +568,7 @@ end
SparseMatrixCSC(B::Bidiagonal{Tv}) where Tv = SparseMatrixCSC{Tv,Int}(B)
function SparseMatrixCSC{Tv,Ti}(B::Bidiagonal) where {Tv,Ti}
m = length(B.dv)
m == 0 && return SparseMatrixCSC{Tv,Ti}(zeros(Tv, 0, 0))

colptr = Vector{Ti}(undef, m+1)
colptr[1] = 1
Expand Down