Hack to get a sortperm working for CUDA

sortperm.jl

import Base: zero, one


function uint_type(t)
    s = sizeof(t)
    if s == 2
        Int16
    elseif s == 4
        Int32
    elseif s == 8
        Int64
    else
        throw("Invalid size")
    end
end

# CUDA Quicksort kernel needs these to be defined to sort tuples
zero(::Type{Tuple{T1,T2}}) where {T1,T2} = (T1(0), T2(0))
one(::Type{Tuple{T1,T2}}) where {T1,T2} = (T1(1), T2(1))


function _sortperm(a::AbstractVector{<:Number})
    T1, T2 = eltype(a), uint_type(eltype(a))
    N = length(a)
    indexed = similar(a, T2, (2, N))
    indexed[1, :] .= reinterpret(T2, a)
    indexed[2, :] .= T2(1):T2(N)
    indexed = reshape(reinterpret(Tuple{T1,T2}, indexed), N)
    sort!(indexed)
    @views reinterpret(T2, reshape(indexed, 1, N))[2, :]
end