Lua - local vs global performance

local_vs_global.lua

local NUMBER_OF_CALLS = 20
x = {}

for i = 1, 1e4 do
	x[string.char(math.random(128))] = "foo"
end

function x.test()
	local o = {}

	for i = 1, 1e6 do
		local t = {foo = function() return i end}
		table.insert(o, t)
	end

	for i = #o, 1, -1 do
		table.remove(o, i)
	end
end

local b = {}

for i = 1, NUMBER_OF_CALLS do
	local start = os.clock()
	x.test()
	local res = (os.clock() - start) * 1000
	table.insert(b, res)
	print("GLOBAL", string.format("%.2f ms", res))
end

local bb = 0

for _, v in ipairs(b) do
	bb = bb + v
end

print()
print("Average (GLOBAL)", string.format("%.2f ms", bb / #b))
print("---------------------------------")
print()


local test = x.test
b = {}

for i = 1, NUMBER_OF_CALLS do
	local start = os.clock()
	test()
	local res = (os.clock() - start) * 1000
	table.insert(b, res)
	print("LOCAL", string.format("%.2f ms", res))
end

bb = 0

for _, v in ipairs(b) do
	bb = bb + v
end

print()
print("Average (LOCAL)", string.format("%.2f ms", bb / #b))
print("---------------------------------")
print()