Slowdown with reinterpret

General Usage Performance
, ,
3

You can cast the memory region. However, notice that this is somewhat unsafe and you will need to take care for Julia GC do not deallocate xdata:

function myfunc3(n::Int)
    xdata = Vector{Tuple{Int,Int,Int}}(undef, n)
    GC.@preserve xdata begin
        p = Base.unsafe_convert(Ptr{Int}, xdata)
        x = unsafe_wrap(Array, p, 3 * n)

        for i in eachindex(x)
          x[i] = i
        end
    end
    return xdata
end

julia> @btime myfunc1($n);
  2.484 ms (2 allocations: 22.89 MiB)

julia> @btime myfunc2($n);
  16.915 ms (2 allocations: 22.89 MiB)

julia> @btime myfunc3($n);
  2.487 ms (3 allocations: 22.89 MiB)
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