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Avoid copy in empty bidiag ldiv! #1275

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Merged
merged 2 commits into from
Apr 8, 2025
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Avoid copy in empty bidiag ldiv! #1275

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abbd086
Avoid copy in empty bidiag `ldiv!`
jishnub Apr 8, 2025
02045d4
Update error messages
jishnub Apr 8, 2025
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12 changes: 6 additions & 6 deletions src/bidiag.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -1250,19 +1250,19 @@ end
ldiv!(A::Bidiagonal, b::AbstractVecOrMat) = @inline ldiv!(b, A, b)
function ldiv!(c::AbstractVecOrMat, A::Bidiagonal, b::AbstractVecOrMat)
require_one_based_indexing(c, A, b)
N = size(A, 2)
N = size(A, 1)
mb, nb = size(b, 1), size(b, 2)
if N != mb
throw(DimensionMismatch(lazy"second dimension of A, $N, does not match first dimension of b, $mb"))
dimstr = b isa AbstractVector ? "length" : "first dimension"
throw(DimensionMismatch(LazyString(lazy"the first dimension of the Bidiagonal matrix, $N, ",
lazy"does not match the $dimstr of the right-hand-side, $mb")))
end
mc, nc = size(c, 1), size(c, 2)
if mc != mb || nc != nb
throw(DimensionMismatch(lazy"size of result, ($mc, $nc), does not match the size of b, ($mb, $nb)"))
throw(DimensionMismatch(lazy"size of result, $(size(c)), does not match the size of b, $(size(b))"))
end

if N == 0
return copyto!(c, b)
end
N == 0 && return c # in this case c and b are also empty

zi = findfirst(iszero, A.dv)
isnothing(zi) || throw(SingularException(zi))
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11 changes: 11 additions & 0 deletions test/bidiag.jl
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Expand Up @@ -1180,4 +1180,15 @@ end
@test !isreal(im*M)
end

@testset "ldiv! error message" begin
C = zeros(2)
B = Bidiagonal(1:0, 1:0, :U)
msg = "size of result, (2,), does not match the size of b, (0, 1)"
@test_throws msg ldiv!(C, B, zeros(0,1))
msg = "the first dimension of the Bidiagonal matrix, 0, does not match the length of the right-hand-side, 2"
@test_throws msg ldiv!(C, B, zeros(2))
msg = "the first dimension of the Bidiagonal matrix, 0, does not match the first dimension of the right-hand-side, 2"
@test_throws msg ldiv!(C, B, zeros(2,1))
end

end # module TestBidiagonal