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LinearAlgebra: Type-stability in broadcasting numbers over Bidiagonal #54067

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Merged
merged 3 commits into from
May 2, 2024
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LinearAlgebra: Type-stability in broadcasting numbers over Bidiagonal #54067

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2588d66
LinearAlgebra: Type-stability in broadcasting numbers over Bidiagonal
jishnub Apr 12, 2024
3aaca7c
count_structedmatrix instead of find_uplo flag
jishnub May 1, 2024
18943f3
Update stdlib/LinearAlgebra/src/structuredbroadcast.jl
N5N3 May 2, 2024
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4 changes: 3 additions & 1 deletion stdlib/LinearAlgebra/src/structuredbroadcast.jl
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Expand Up @@ -78,7 +78,7 @@ find_uplo(bc::Broadcasted) = mapfoldl(find_uplo, merge_uplos, Broadcast.cat_nest
function structured_broadcast_alloc(bc, ::Type{Bidiagonal}, ::Type{ElType}, n) where {ElType}
uplo = n > 0 ? find_uplo(bc) : 'U'
n1 = max(n - 1, 0)
if uplo == 'T'
if count_structedmatrix(Bidiagonal, bc) > 1 && uplo == 'T'
return Tridiagonal(Array{ElType}(undef, n1), Array{ElType}(undef, n), Array{ElType}(undef, n1))
end
return Bidiagonal(Array{ElType}(undef, n),Array{ElType}(undef, n1), uplo)
Expand Down Expand Up @@ -135,6 +135,8 @@ iszerodefined(::Type{<:Number}) = true
iszerodefined(::Type{<:AbstractArray{T}}) where T = iszerodefined(T)
iszerodefined(::Type{<:UniformScaling{T}}) where T = iszerodefined(T)

count_structedmatrix(T, bc::Broadcasted) = sum(Base.Fix2(isa, T), Broadcast.cat_nested(bc); init = 0)

fzeropreserving(bc) = (v = fzero(bc); !ismissing(v) && (iszerodefined(typeof(v)) ? iszero(v) : v == 0))
# Like sparse matrices, we assume that the zero-preservation property of a broadcasted
# expression is stable. We can test the zero-preservability by applying the function
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18 changes: 18 additions & 0 deletions stdlib/LinearAlgebra/test/structuredbroadcast.jl
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Expand Up @@ -96,6 +96,24 @@ using Test, LinearAlgebra
@test broadcast!(*, Z, X, Y) == broadcast(*, fX, fY)
end
end

@testset "type-stability in Bidiagonal" begin
B2 = @inferred (B -> .- B)(B)
@test B2 isa Bidiagonal
@test B2 == -1 * B
B2 = @inferred (B -> B .* 2)(B)
@test B2 isa Bidiagonal
@test B2 == B + B
B2 = @inferred (B -> 2 .* B)(B)
@test B2 isa Bidiagonal
@test B2 == B + B
B2 = @inferred (B -> B ./ 1)(B)
@test B2 isa Bidiagonal
@test B2 == B
B2 = @inferred (B -> 1 .\ B)(B)
@test B2 isa Bidiagonal
@test B2 == B
end
end

@testset "broadcast! where the destination is a structured matrix" begin
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