arr.lua

local N = 10000
local function run_original_proxy()
	local arr = setmetatable({length = 0}, {
        __newindex = function(t,k,v)
            if type(k) == 'number' and k >= t.length then
                t.length = k + 1
            end
            rawset(t,k,v)
        end
    })

	local t1 = os.clock()

	for i = 1, N do
		arr[i] = i
	end

	local t2 = os.clock()

	for i = 1, N do 
		arr[i] = -arr[i]
	end

	local t3 = os.clock()
	
    return t2 - t1, t3 - t2
end

local function run_simple_proxy()
    local data = {}
	local arr = setmetatable({length = 0}, {
        __newindex = function(t,k,v)
            local len = t.length
            t.length = k >= len and (k + 1) or len
            rawset(t,k,v)
        end
    })

	local t1 = os.clock()

	for i = 1, N do
		arr[i] = i
	end

	local t2 = os.clock()

	for i = 1, N do 
		arr[i] = -arr[i]
	end

	local t3 = os.clock()
	
    return t2 - t1, t3 - t2
end

local function run_without_proxy()
    local data = {}
	local arr = {}

	local t1 = os.clock()

	for i = 1, N do
		arr[i] = i
	end

	local t2 = os.clock()

	for i = 1, N do 
		arr[i] = -arr[i]
	end

	local t3 = os.clock()
	
    return t2 - t1, t3 - t2
end

local time = {
    simple = {},
    original = {},
    without = {}
}

local function get_avg_time(arr)
    local sum = {
        init = 0,
        modify = 0
    }
    for i = 1, #arr do
        sum.init = sum.init + arr[i].init
        sum.modify = sum.modify + arr[i].modify
    end
    sum.init = sum.init / #arr
    sum.modify = sum.modify / #arr
    return sum
end

for i = 1, 100 do
    print(i .. "/100")
    local result = {run_simple_proxy()}
    table.insert(time.simple, {init = result[1], modify = result[2]})
    result = {run_original_proxy()}
    table.insert(time.original, {init = result[1], modify = result[2]})
    result = {run_without_proxy()}
    table.insert(time.without, {init = result[1], modify = result[2]})
end

local average = {
    simple = get_avg_time(time.simple),
    original = get_avg_time(time.original),
    without = get_avg_time(time.without)
}

print("average time original metatable")
print("init:", average.original.init, "modify:", average.original.modify)

print("average time simple metatable")
print("init:", average.simple.init, "modify:", average.simple.modify)

print("average time without metatable")
print("init:", average.without.init, "modify:", average.without.modify)