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Only apply Base.Sort.SubArrayOptimization when iszero(v.offset1) #59572

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Merged
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Sep 17, 2025
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Only apply Base.Sort.SubArrayOptimization when iszero(v.offset1) #59572

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684086d
Only apply SubArrayOptimization when iszero(v.offset1)
LilithHafner Sep 16, 2025
ac33e5a
Test the behavior in issue #59569
LilithHafner Sep 16, 2025
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7 changes: 5 additions & 2 deletions base/sort.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -563,12 +563,15 @@ function _sort!(v::UnwrappableSubArray, a::SubArrayOptimization, o::Ordering, kw
@getkw lo hi
# @assert v.stride1 == 1
parent = v.parent
if parent isa Array && !(parent isa Vector) && hi - lo < 100
if parent isa Array && !(parent isa Vector) && hi - lo < 100 || !iszero(v.offset1)
# vec(::Array{T, ≠1}) allocates and is therefore somewhat expensive.
# We don't want that for small inputs.

# Additionally, if offset1 is non-zero, then this optimization is incompatible with
# algorithms that track absolute first and last indices (e.g. ScratchQuickSort)
_sort!(v, a.next, o, kw)
else
_sort!(vec(parent), a.next, o, (;kw..., lo = lo + v.offset1, hi = hi + v.offset1))
_sort!(vec(parent), a.next, o, kw)
end
end

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5 changes: 5 additions & 0 deletions test/sorting.jl
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Expand Up @@ -1140,6 +1140,11 @@ end
end
end

@testset "partialsort! for UnwrappableSubArray with non-zero offset on 1.11 (#59569)" begin
a = reshape(6000:-1:1, 1000, :) |> collect;
@test partialsort!(view(copy(a), :, 6), 500:501) == [500, 501]
end

# This testset is at the end of the file because it is slow.
@testset "searchsorted" begin
numTypes = [ Int8, Int16, Int32, Int64, Int128,
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