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Apply InitialOptimizations more consistently in sorting #47946

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Dec 22, 2022
Merged

Apply InitialOptimizations more consistently in sorting #47946

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f770e72
Apply InitialOptimizations by default in several cases when it was pr…
Dec 21, 2022
22a8dcc
fixup for MissingOptimization
Dec 21, 2022
22ed59f
fix stability in the sortperm union with missing case
Dec 21, 2022
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47 changes: 38 additions & 9 deletions base/sort.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,7 @@ issorted(itr;
issorted(itr, ord(lt,by,rev,order))

function partialsort!(v::AbstractVector, k::Union{Integer,OrdinalRange}, o::Ordering)
_sort!(v, QuickerSort(k), o, (;))
_sort!(v, InitialOptimizations(QuickerSort(k)), o, (;))
maybeview(v, k)
end

Expand Down Expand Up @@ -566,8 +566,30 @@ function _sort!(v::AbstractVector, a::MissingOptimization, o::Ordering, kw)
if nonmissingtype(eltype(v)) != eltype(v) && o isa DirectOrdering
lo, hi = send_to_end!(ismissing, v, o; lo, hi)
_sort!(WithoutMissingVector(v, unsafe=true), a.next, o, (;kw..., lo, hi))
elseif eltype(v) <: Integer && o isa Perm{DirectOrdering} && nonmissingtype(eltype(o.data)) != eltype(o.data)
lo, hi = send_to_end!(i -> ismissing(@inbounds o.data[i]), v, o)
elseif eltype(v) <: Integer && o isa Perm && o.order isa DirectOrdering &&
nonmissingtype(eltype(o.data)) != eltype(o.data) &&
all(i === j for (i,j) in zip(v, eachindex(o.data)))
# TODO make this branch known at compile time
# This uses a custom function because we need to ensure stability of both sides and
# we can assume v is equal to eachindex(o.data) which allows a copying partition
# without allocations.
lo_i, hi_i = lo, hi
for (i,x) in zip(eachindex(o.data), o.data)
if ismissing(x) == (o.order == Reverse) # should i go at the beginning?
v[lo_i] = i
lo_i += 1
else
v[hi_i] = i
hi_i -= 1
end
end
reverse!(v, lo_i, hi)
if o.order == Reverse
lo = lo_i
else
hi = hi_i
end

_sort!(v, a.next, Perm(o.order, WithoutMissingVector(o.data, unsafe=true)), (;kw..., lo, hi))
else
_sort!(v, a.next, o, kw)
Expand Down Expand Up @@ -1160,7 +1182,9 @@ end
"""
InitialOptimizations(next) <: Algorithm

Attempt to apply a suite of low-cost optimizations to the input vector before sorting.
Attempt to apply a suite of low-cost optimizations to the input vector before sorting. These
optimizations may be automatically applied by the `sort!` family of functions when
`alg=InsertionSort`, `alg=MergeSort`, or `alg=QuickSort` is passed as an argument.

`InitialOptimizations` is an implementation detail and subject to change or removal in
future versions of Julia.
Expand Down Expand Up @@ -1347,7 +1371,7 @@ function sort!(v::AbstractVector{T};
rev::Union{Bool,Nothing}=nothing,
order::Ordering=Forward,
scratch::Union{Vector{T}, Nothing}=nothing) where T
_sort!(v, alg, ord(lt,by,rev,order), (;scratch))
_sort!(v, maybe_apply_initial_optimizations(alg), ord(lt,by,rev,order), (;scratch))
v
end

Expand Down Expand Up @@ -1474,7 +1498,7 @@ function partialsortperm!(ix::AbstractVector{<:Integer}, v::AbstractVector,
end

# do partial quicksort
_sort!(ix, QuickerSort(k), Perm(ord(lt, by, rev, order), v), (;))
_sort!(ix, InitialOptimizations(QuickerSort(k)), Perm(ord(lt, by, rev, order), v), (;))

maybeview(ix, k)
end
Expand Down Expand Up @@ -1679,11 +1703,11 @@ function sort(A::AbstractArray{T};
pdims = (dim, setdiff(1:ndims(A), dim)...) # put the selected dimension first
Ap = permutedims(A, pdims)
Av = vec(Ap)
sort_chunks!(Av, n, alg, order, scratch)
sort_chunks!(Av, n, maybe_apply_initial_optimizations(alg), order, scratch)
permutedims(Ap, invperm(pdims))
else
Av = A[:]
sort_chunks!(Av, n, alg, order, scratch)
sort_chunks!(Av, n, maybe_apply_initial_optimizations(alg), order, scratch)
reshape(Av, axes(A))
end
end
Expand Down Expand Up @@ -1746,7 +1770,7 @@ function sort!(A::AbstractArray{T};
rev::Union{Bool,Nothing}=nothing,
order::Ordering=Forward, # TODO stop eagerly over-allocating.
scratch::Union{Vector{T}, Nothing}=similar(A, size(A, dims))) where T
__sort!(A, Val(dims), alg, ord(lt, by, rev, order), scratch)
__sort!(A, Val(dims), maybe_apply_initial_optimizations(alg), ord(lt, by, rev, order), scratch)
end
function __sort!(A::AbstractArray{T}, ::Val{K},
alg::Algorithm,
Expand Down Expand Up @@ -1911,6 +1935,11 @@ Characteristics:
"""
const MergeSort = MergeSortAlg()

maybe_apply_initial_optimizations(alg::Algorithm) = alg
maybe_apply_initial_optimizations(alg::QuickSortAlg) = InitialOptimizations(alg)
maybe_apply_initial_optimizations(alg::MergeSortAlg) = InitialOptimizations(alg)
maybe_apply_initial_optimizations(alg::InsertionSortAlg) = InitialOptimizations(alg)

# selectpivot!
#
# Given 3 locations in an array (lo, mi, and hi), sort v[lo], v[mi], v[hi]) and
Expand Down