Speed up permsort by utilizing stability of the default sorting algorithm #47587
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@@ -560,13 +560,49 @@ elements that are not | |
| @inline send_to_end!(f::F, v::AbstractVector, ::ReverseOrdering, end_stable=false; lo, hi) where F <: Function = | ||
| end_stable ? (send_to_end!(!f, v; lo, hi)+1, hi) : (hi-send_to_end!(f, view(v, hi:-1:lo))+1, hi) | ||
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| """ | ||
| send_to_end_stable!(f::Function, v::AbstractVector; [lo, hi]) | ||
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| Send every element of `v` for which `f` returns `true` to the end of the vector `out` and return | ||
| the index of the last element which for which `f` returns `false`. | ||
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| `send_to_end_stable!(f, v, out, lo, hi)` is equivalent to `send_to_end_stable!(f, view(v, lo:hi), view(out, lo:hi))+lo-1` | ||
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| Preserves the order of the elements. | ||
| """ | ||
| function send_to_end_stable!(f::F, v::AbstractVector, out::AbstractVector; lo=firstindex(v), hi=lastindex(v)) where F <: Function | ||
| offset = 0 | ||
| @inbounds begin | ||
| while lo <= hi | ||
| x = v[lo] | ||
| fx = f(x)::Bool | ||
| out[(fx ? hi : lo) - offset] = x | ||
| offset += fx | ||
| lo += 1 | ||
| end | ||
| end | ||
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| # This is similar to the partition function | ||
| pivot_index = lo-offset-1 | ||
| # out[<=pivot_index] <* f(x) = false | ||
| # out[>pivot_index] >* f(x) = true | ||
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| # Make the results stable | ||
| reverse!(out, pivot_index+1, hi) | ||
| return pivot_index | ||
| end | ||
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| @inline send_to_end_stable!(f::F, v::AbstractVector, out::AbstractVector, ::ForwardOrdering; lo, hi) where F <: Function = | ||
| (lo, send_to_end_stable!(f, v, out; lo, hi)) | ||
| @inline send_to_end_stable!(f::F, v::AbstractVector, out::AbstractVector, ::ReverseOrdering; lo, hi) where F <: Function = | ||
| (hi-send_to_end_stable!(f, view(v, hi:-1:lo), view(out, hi:-1:lo))+1, hi) | ||
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| function _sort!(v::AbstractVector, a::MissingOptimization, o::Ordering, kw) | ||
| @getkw lo hi | ||
| 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 || o isa PermT) && 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 | ||
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@@ -590,7 +626,8 @@ function _sort!(v::AbstractVector, a::MissingOptimization, o::Ordering, kw) | |
| hi = hi_i | ||
| end | ||
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| PermT = o isa PermFast ? PermFast : Perm | ||
| _sort!(v, a.next, PermT(o.order, WithoutMissingVector(o.data, unsafe=true)), (;kw..., lo, hi)) | ||
| else | ||
| _sort!(v, a.next, o, kw) | ||
| end | ||
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@@ -618,26 +655,39 @@ after_zero(::ForwardOrdering, x) = !signbit(x) | |
| after_zero(::ReverseOrdering, x) = signbit(x) | ||
| is_concrete_IEEEFloat(T::Type) = T <: Base.IEEEFloat && isconcretetype(T) | ||
| function _sort!(v::AbstractVector, a::IEEEFloatOptimization, o::Ordering, kw) | ||
| @getkw lo hi scratch | ||
| if is_concrete_IEEEFloat(eltype(v)) && o isa DirectOrdering | ||
| lo, hi = send_to_end!(isnan, v, o, true; lo, hi) | ||
| iv = reinterpret(UIntType(eltype(v)), v) | ||
| j = send_to_end!(x -> after_zero(o, x), v; lo, hi) | ||
| scratch = _sort!(iv, a.next, Reverse, (;kw..., lo, hi=j)) | ||
| if scratch === nothing # Union split | ||
| _sort!(iv, a.next, Forward, (;kw..., lo=j+1, hi, nothing)) | ||
| else | ||
| _sort!(iv, a.next, Forward, (;kw..., lo=j+1, hi, scratch)) | ||
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There was a problem hiding this comment. @LilithHafner Btw, is There was a problem hiding this comment. I recall that removing the if statement entirely introduced dynamic dispatch. IICU, all of type inference is an implementation detail, so I'm not totally sure, but I believe that we need an if statement to force union splitting though it works well whether we use |
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| end | ||
| elseif eltype(v) <: Integer && (o isa Perm || o isa PermFast) && o.order isa DirectOrdering && is_concrete_IEEEFloat(eltype(o.data)) | ||
| if o isa Perm | ||
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| lo, hi = send_to_end!(i -> isnan(@inbounds o.data[i]), v, o.order, true; lo, hi) | ||
| j = send_to_end!(i -> after_zero(o.order, @inbounds o.data[i]), v; lo, hi) | ||
| PermT = Perm | ||
| kw = (;kw..., lo, hi=j) | ||
| else | ||
| scratch, t = make_scratch(scratch, eltype(v), hi-lo+1) | ||
| lo2, hi2 = send_to_end_stable!(i -> isnan(@inbounds o.data[i]), v, scratch, o.order; lo, hi) | ||
| ran = lo < lo2 ? (lo:lo2-1) : (hi2+1:hi) | ||
| v[ran] = view(scratch, ran) | ||
| lo, hi = lo2, hi2 | ||
| j = send_to_end_stable!(i -> after_zero(o.order, @inbounds o.data[i]), scratch, v; lo, hi) | ||
| PermT = PermFast | ||
| kw = (;kw..., lo, hi=j, scratch=scratch) | ||
| end | ||
| ip = reinterpret(UIntType(eltype(o.data)), o.data) | ||
| scratch = _sort!(v, a.next, Perm(Reverse, ip), kw) | ||
| if scratch === nothing # Union split | ||
| _sort!(v, a.next, PermT(Forward, ip), (;kw..., lo=j+1, hi, nothing)) | ||
| else | ||
| _sort!(v, a.next, PermT(Forward, ip), (;kw..., lo=j+1, hi, scratch)) | ||
| end | ||
| else | ||
| _sort!(v, a.next, o, kw) | ||
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@@ -1579,7 +1629,11 @@ function _sortperm(A::AbstractArray; alg, order, scratch, dims...) | |
| end | ||
| end | ||
| ix = copymutable(LinearIndices(A)) | ||
| if alg == DEFAULT_STABLE | ||
| sort!(ix; alg, order = PermFast(order, vec(A)), scratch, dims...) | ||
| else | ||
| sort!(ix; alg, order = Perm(order, vec(A)), scratch, dims...) | ||
| end | ||
| end | ||
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@@ -1636,11 +1690,11 @@ julia> sortperm!(p, A; dims=2); p | |
| if !initialized | ||
| ix .= LinearIndices(A) | ||
| end | ||
| PermT = alg == DEFAULT_STABLE ? PermFast : Perm | ||
| if rev === true | ||
| sort!(ix; alg, order = PermT(ord(lt, by, rev, order), vec(A)), scratch, dims...) | ||
| else | ||
| sort!(ix; alg, order = PermT(ord(lt, by, nothing, order), vec(A)), scratch, dims...) | ||
| end | ||
| end | ||
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It would be nice to have code re-use; the loop here is almost exactly the same as the loops in
partition!There was a problem hiding this comment.
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It would be nice. However,
partition!left a pivot on the place and split to two parts with. Thus it seems challenging.