applyreduce has 1 allocation where sum does not

[asinghvi17]

using Chairmarks
import GeometryOps as GO, GeoInterface as GI


function _area(p::GI.LinearRing)
    first_point = p.geom[1]
    area = 0.0
    for next_point in view(p.geom, 2:length(p.geom))
        area += first_point[1] * next_point[2] - first_point[2] * next_point[1]
        first_point = next_point
    end
    return area
end

_area(p::GI.Polygon) = if length(p.geom) == 1
    _area(p.geom[1])
else
    _area(p.geom[1]) - sum(_area, view(p.geom, 2:length(p.geom)))
end


p = GI.Polygon([GI.LinearRing([(0, 0), (0,1), (1, 1), (1, 0), (0, 0)])])

@be GO.area($p) # ~6 ns
@be _area($p)   # ~7 ns
# These two are at least equivalent - showing that `apply` and `applyreduce` are indeed cost-free.

@be GO.area($([p, p])) # ~17 ns, 1 allocation
@be sum($_area, $([p, p])) # ~15 ns, no allocations
# So there is work to do here.

We need to isolate and remove this allocation!