string to table benchmark test

stringtotablebt.lua

local function subtt(str)
	local t = {}
	for i = 1, #str do
		t[i] = str:sub(i, i)
	end
	return t
end

local function gsubtt(str)
	local t = {}
	local i = 1
	str:gsub(".", function(c)
		t[i] = c
		i = i+1
	end)
	return t
end

local txt = [[
local function subtt(str)
	local t = {}
	for i = 1, #str do
		t[i] = str:sub(i, i)
	end
	return t
end

local function gsubtt(str)
	local t = {}
	local i = 1
	str:gsub(".", function(c)
		t[i] = c
		i = i+1
	end)
	return t
end
]]

local function bt()
	local s = benchmark_function(subtt, txt)
	local g = benchmark_function(gsubtt, txt)
	print("s", s)
	print("g", g)
	print(dump(subtt(txt)) == dump(gsubtt(txt)))
end

minetest.register_chatcommand("bt", {
	params = "a",
	description = "ahref",
	func = bt,
})

--[[ result:
	subtt is ~between 3 (long txt) and 6 (short text) times as fast as gsubtt
]]



------------------------------------------------------------------------------------------------------



function string.charIter(txt)
	-- return txt:gmatch"."
	local i = 0
	local l = #txt
	return function()
		i = i+1
		if i > l then
			return
		end
		return txt:sub(i, i), i
	end
end

local function gsubtt(str)
	for c in str:gmatch"." do
	end
end

local function subtt(str)
	for c,i in str:charIter() do
	end
end

local txt = [[
local function subtt(str)
	local t = {}
	for i = 1, #str do
		t[i] = str:sub(i, i)
	end
	return t
end

local function gsubtt(str)
	local t = {}
	local i = 1
	str:gsub(".", function(c)
		t[i] = c
		i = i+1
	end)
	return t
end
]]

local function bt()
	local s = benchmark_function(subtt, txt)
	local g = benchmark_function(gsubtt, txt)
	print("s", s)
	print("g", g)
	print(dump(subtt(txt)) == dump(gsubtt(txt)), s/g)
end

minetest.register_chatcommand("bt", {
	params = "a",
	description = "ahref",
	func = bt,
})

--[[ result:
s	200267.1995992
g	68422.226311095
true	2.9269319400489
2016-07-05 10:22:05: ACTION[Server]: msg to singleplayer: "@#f3d2ff) (4.000136 s)@#ffffff)"
s	204012.3979938
g	69244.223023108
true	2.9462731919993
2016-07-05 10:22:11: ACTION[Server]: msg to singleplayer: "@#f3d2ff) (4.000134 s)@#ffffff)"
s	205426.89728655
g	68805.465597267
true	2.9856188822115
2016-07-05 10:22:23: ACTION[Server]: msg to singleplayer: "@#f3d2ff) (4.000122 s)@#ffffff)"
]]

http://stackoverflow.com/questions/20423406/lua-convert-string-to-table