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Equality/hash edge cases for QRCompactWY #1582

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Equality/hash edge cases for QRCompactWY #1582

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a1e55df
Equality/`hash` edge cases for `QRCompactWY`
jishnub Apr 27, 2026
43a3be6
Trim empty lines
jishnub Apr 27, 2026
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5 changes: 4 additions & 1 deletion src/qr.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -148,7 +148,8 @@ Base.iterate(S::QRCompactWY, ::Val{:done}) = nothing
#
function _triuppers_qr(T)
blocksize, cols = size(T)
return Iterators.map(0:div(cols - 1, blocksize)) do i
nblocks = iszero(cols) || iszero(blocksize) ? 0 : cld(cols, blocksize)
return Iterators.map(range(0, length=nblocks)) do i
n = min(blocksize, cols - i * blocksize)
return UpperTriangular(view(T, 1:n, (1:n) .+ i * blocksize))
end
Expand All @@ -158,9 +159,11 @@ function Base.hash(F::QRCompactWY, h::UInt)
return hash(F.factors, foldr(hash, _triuppers_qr(F.T); init=hash(QRCompactWY, h)))
end
function Base.:(==)(A::QRCompactWY, B::QRCompactWY)
size(A.T) == size(B.T) || return false
return A.factors == B.factors && all(splat(==), zip(_triuppers_qr.((A.T, B.T))...))
end
function Base.isequal(A::QRCompactWY, B::QRCompactWY)
size(A.T) == size(B.T) || return false
return isequal(A.factors, B.factors) && all(zip(_triuppers_qr.((A.T, B.T))...)) do (a, b)
isequal(a, b)::Bool
end
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21 changes: 20 additions & 1 deletion test/qr.jl
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Expand Up @@ -517,7 +517,7 @@ end
# this should have worked before, Q is square, and R is 0 × 0:
A_zero_cols = rand(F, dimA, 0)
qr_zero_cols = qr(A_zero_cols)
@test size(qr_zero_cols.Q) == (dimA, dimA)
@test size(qr_zero_cols.Q) == (dimA, dimA)
@test size(qr_zero_cols.R) == (0, 0)
@test qr_zero_cols.Q == LinearAlgebra.I(dimA)

Expand All @@ -542,4 +542,23 @@ end
@test rank(qr([1.0 2.0 3.0; 4.0 5.0 6.0 ; 7.0 8.0 9.0], ColumnNorm())) == 2
end

@testset "QRCompactWY equality/hash" begin
@testset "$(size(A))" for A in (zeros(0, 0), zeros(0, 3), zeros(3, 0))
F, G = qr(A), qr(A)
@test F == G
@test isequal(F, G)
@test hash(F) == hash(G)
end

@testset "QRCompactWY equality checks T shape" begin
# This is a contrived example, but ensures that we don't violate the hash contract
F = LinearAlgebra.QRCompactWY(zeros(1, 1), reshape([1.0], 1, 1))
G = LinearAlgebra.QRCompactWY(zeros(1, 1), reshape([1.0 99.0], 1, 2))

@araujoms araujoms Apr 29, 2026

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Why is G even valid, though? Shouldn't the constructor just throw an error?

@jishnub jishnub May 5, 2026

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Perhaps it should


@test F != G
@test !isequal(F, G)
@test hash(F) != hash(G)
end
end

end # module TestQR
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